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Title: Carvacrol as a Bacterial Growth Inhibitor: Mechanisms, Efficacy, and Potential Applications
Carvacrol as a Key Antibacterial Constituent in Plant Essential Oils
Carvacrol as a Key Antibacterial Component in Essential Oils from Lamiaceae and Other Plant Species
Carvacrol is a key antibacterial component in essential oils (EOs) from multiple Lamiaceae species, including thyme, oregano, savory, and Thymus accessions, with variable abundance across sources and extraction methods. Its antibacterial efficacy is well-documented, with activity linked to membrane disruption, synergistic interactions with other EO components, and effects on bacterial adhesion and protein interactions. Mechanistically, carvacrol’s phenolic hydroxyl group drives membrane permeability changes, and its efficacy is enhanced by precursors like p-cymene, while Gram-positive bacteria are more sensitive than Gram-negative counterparts due to outer membrane differences.
Carvacrol Content in Essential Oils from Lamiaceae and Non-Lamiaceae Species
| Source | Carvacrol Content | Citation(s) |
|---|---|---|
| Thyme EO | 12.42% | [1] |
| Oregano EO | Up to 81.85% | [1], [2] |
| Thymus species (range) | 4.37%–42.14% | [3] |
| T. carmanicus | 42.14% | [3] |
| T. fedtschenkoi-1 | 38.52% | [3] |
| T. transcaspicus | 37.11% | [3] |
| Greek oregano EO (chemotype study) | 37.21% | [4] |
| Greek oregano EO (mixed report) | 72.0% | [2] |
| Spanish oregano EO | 42.0% | [2] |
| Savoury EO | 32.8% | [2] |
| Summer savory EO (hydrodistillation, HD) | 48.7% | [5] |
| Summer savory EO (microwave-assisted hydrodistillation, MAHD) | 47.7% | [5] |
| T. spicata var. Spicata EO (solvent-free microwave extraction, SFME) | 44.8% | [6] |
| T. spicata var. Spicata EO (HD) | 36.1% | [6] |
| Mexican oregano EO | 26.9% | [7] |
| Thymus daenensis ecotypes (range) | 5.14%–51.89% | [8] |
| Thymus capitatus EO | 68.07% | [9] |
| Origanum EOs (4 of 9 samples, range) | 58%–86% (relative percentage) | [10] |
| Satureja subspicata EO | 16.76% | [11] |
| Satureja hortensis L. EO | Major constituent | [12] |
| Oregano EO (high-content report) | 91.6% | [13] |
| Satureja thymbra EO | 29.2% | [14] |
| Origanum vulgare EO | 14.5% | [15] |
| Thymus vulgaris “carvacrol” chemotype EO | 44.66% | [16] |
| T. zygis EO (as part of combined major components) | 75.6% (total with thymol, p-cymene, terpinene, linalool) | [17] |
| Wild O. vulgare subsp. hirtum EO (range) | 7.5%–82.9% | [18] |
| Cultivated O. vulgare subsp. hirtum EO (range) | 5.3%–85.4% | [18] |
| Lippia micromera leaf EO | 22.0% | [19] |
| Plectranthus amboinicus leaf EO | 51.3% | [19] |
| Salvia macrantha EO (Kaleybar samples) | Up to 48.6% | [20] |
| A. debrana roots (via SDE) | 4.15% | [21] |
| OVEO | Up to 81.98% | [22] |
| A. tenuifolia (range across growth stages) | 30.85%–34.11% | [23] |
| Greek oregano EO (high-content report) | 84.4% | [24] |
| S. montana | 306 g L⁻¹ | [25] |
| T. vulgaris (accession 1) | 4.62% | [26] |
| T. vulgaris (accession 2) | 75.27% | [27] |
| Oregano EO (mixed report) | 72.9% | [28] |
| SEO | 14.3% | [29] |
| P. longiflora (non-Lamiaceae) | Major component | [30] |
| Cluster Group I (EO samples) | 54.9% | [31] |
| Cluster Group II (EO samples, range) | Up to 96.7% (mean 76.2%) | [31] |
| Oregano EO (variability range) | 31%–81% | [32] |
| Thymus population 'II' | 64.6% | [33] |
Antibacterial Efficacy of Carvacrol and Carvacrol-Rich Essential Oils
| Source | Antibacterial Activity Metric | Target Pathogens/Groups | Citation(s) |
|---|---|---|---|
| Greek oregano, savoury, Spanish oregano EOs | IC₅₀ 26–88 μg mL⁻¹ | All tested pathogens | [2] |
| Thyme EO (high carvacrol) | Highest inhibitory activity, comparable to control antibiotics | Not specified | [34] |
| Sage EO (0.69% carvacrol) | Lowest activity among tested EOs | Not specified | [34] |
| Greek oregano EO (37.21% carvacrol) | MIC 0.25–1 mg mL⁻¹; MBC 0.5–2 mg mL⁻¹ | Gram-negative (E. coli, Salmonella enterica); Gram-positive (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus) | [4] |
| Carvacrol (pure) | Most active component of ECO (26.25% carvacrol) | Fusobacterium nucleatum, Porphyromonas gingivalis (planktonic cells) | [35] |
| Oregano EO (2% in QSMF films) | Reduced LAB counts by <1 log CFU/g; extended shelf life to 15–18 days (control: 7–9 days) | Lactic acid bacteria (rainbow trout fillets) | [1] |
| T. capitatus EO | MIC 1–2 μg ml⁻¹; MBC 1–40 μg ml⁻¹ | Not specified | [9] |
| Pure carvacrol | MIC 2.5–50 μg ml⁻¹; MBC 5–100 μg ml⁻¹ | Not specified | [9] |
| Origanum EOs (carvacrol chemotype) | MIC 0.15 mg/mL (H. influenzae, H. parainfluenzae); MIC 0.6 mg/mL (MRSA) | H. influenzae, H. parainfluenzae, methicillin-resistant S. aureus (MRSA) | [10] |
| S. subspicata EO | Inhibition zones 28–34 mm; MIC 0.09 μl/ml | Gram-positive (S. aureus) | [11] |
| S. hortensis L. EO | MIC 0.125 μl/ml | All tested bacteria | [12] |
| Oregano EO (91.6% carvacrol) | 99.9% elimination of initial inoculum (5 min, 0.5 mg/mL) | S. pyogenes | [13] |
| S. thymbra EO | Inhibited growth initiation (0.1% vol/vol effective) | L. monocytogenes, Salmonella Enteritidis (enhanced at high salt/low temp) | [14] |
| Origanum vulgare EO | MIC <5 mg mL⁻¹ | All tested bacterial strains | [15] |
| Thymus vulgaris “carvacrol” chemotype EO | MIC 1.25 μL/mL; MBC 5.0 μL/mL | S. mutans | [16] |
| T. zygis EO | MIC 1 mg mL⁻¹; MBC 2 mg mL⁻¹ | Not specified | [17] |
| Wild/cultivated O. vulgare subsp. hirtum EOs | Antibacterial activity | Not specified | [18] |
| L. micromera, P. amboinicus leaf EOs | MIC 0.03–0.12%; MBC 0.12–0.25% | S. aureus, S. epidermidis | [19] |
| S. macrantha EOs (up to 48.6% carvacrol) | MICs, MBCs <100 µg/mL | Not specified | [20] |
| Pure carvacrol (10 μg ml⁻¹) | Inhibited L. monocytogenes adhesion by 49%; lesser E. coli inhibition | Bacterial adhesion to colon epithelium | [9] |
| Pure carvacrol | Interacts with brpA, gbpB, spaP proteins (low affinity) | Not specified (mechanistic) | [16] |
| Carvacrol (vapor-phase) | Inhibited Gram-negative/Gram-positive bacteria; less effective than thymol against S. choleraesuis | S. choleraesuis (comparative) | [36] |
| A. debrana root EO | High antibacterial activity | Not specified | [21] |
| OVEO (81.98% carvacrol) | Potent effects | Not specified | [22] |
| A. tenuifolia EOs | Higher activity than gentamicin/nalidixic acid | Most tested bacteria | [23] |
| Greek oregano EO (84.4% carvacrol) | Inhibition zones 50, 40, 35 mm (4 µl/disc) | S. aureus, B. subtilis, E. coli | [24] |
| P. longiflora EO | Better activity than L. graveolens | Not specified | [30] |
| S. montana EO | MIC 0.80–2.10 µg mL⁻¹ | B. thermosphacta, L. innocua, L. monocytogenes | [25] |
| T. vulgaris (75.27% carvacrol) | MIC 0.05% | S. aureus, E. coli O157:H7, S. typhimurium | [27] |
| Oregano EO (72.9% carvacrol) | Antibacterial activity | Not specified | [28] |
| SEO (14.3% carvacrol) | MIC/MLC 0.125/0.25 μg/ml | S. aureus, P. mirabilis, K. pneumonia | [29] |
| Thymus population 'II' (64.6% carvacrol) | MIC 1/6400 | Enterococcus faecalis | [33] |
| OSS EO | Strong activity attributed to carvacrol/thymol | Not specified | [37] |
| Pure carvacrol | MIC 128–1024 μg/mL (moderate activity) | Not specified | [30] |
Mechanistically, carvacrol disrupts bacterial membranes by disintegrating the outer membrane of Gram-negative bacteria and increasing cytoplasmic membrane permeability, with its phenolic hydroxyl group critical to this effect [38], [2]. Gram-positive bacteria (e.g., S. aureus) are more sensitive than Gram-negative counterparts (e.g., E. coli) due to the latter’s lipopolysaccharide outer membrane restricting hydrophobic compound diffusion [38], [5]. Synergistic interactions enhance efficacy: p-cymene (a carvacrol precursor) swells cell membranes to facilitate carvacrol entry [38], [2], and combinations with p-cymene/phellandrene show synergistic/additive effects against F. nucleatum and P. gingivalis [35]. Biosynthetically, thymol and carvacrol production in Thymus species are negatively correlated (indicating competitive pathways), while p-cymene and total phenolic content are positively correlated (confirming p-cymene as a precursor) [3].
Additional mechanisms include depletion of intracellular ATP pools, reduced ATP synthesis, membrane permeability disruption leading to ion leakage and osmotic disturbances [4], and morphological changes (e.g., reduced size/length of S. pyogenes, ruptured cell structures) [13]. Cell surface damage is observed in S. aureus (sunken/malformed surfaces), E. coli (irregular/collapsed surfaces), and L. monocytogenes (cell destruction, pore formation) [39]. Carvacrol-rich EOs also inhibit biofilm formation: oregano EO reduces S. pyogenes biofilms concentration-dependently [13], and subinhibitory concentrations inhibit biofilm production [39]. The hydroxyl group position influences activity (thymol is more effective against S. choleraesuis than carvacrol vapor-phase) [36], and the phenolic ring is critical (p-cymene lacks activity) [36].
Further supporting evidence includes: high antibacterial activity of A. debrana root EO (linked to carvacrol) [21]; potent effects of OVEO (81.98% carvacrol) [22]; A. tenuifolia EOs (high carvacrol) outperforming gentamicin/nalidixic acid [23]; strong inhibition of S. aureus, B. subtilis, and E. coli by Greek oregano EO (84.4% carvacrol) [24]; better activity of P. longiflora EO (higher carvacrol) than L. graveolens [30]; inhibition of B. thermosphacta, L. innocua, and L. monocytogenes by S. montana EO [25]; MIC 0.05% of T. vulgaris EO (75.27% carvacrol) against S. aureus, E. coli O157:H7, and S. typhimurium [27]; antibacterial activity of oregano EO (72.9% carvacrol) [28]; MIC/MLC 0.125/0.25 μg/ml of SEO (14.3% carvacrol) against S. aureus, P. mirabilis, and K. pneumonia [29]; and high efficacy of Thymus population 'II' (64.6% carvacrol) against E. faecalis [33]. PCA analysis links T. vulgaris EO carvacrol content to stronger activity against Streptococcus spp., E. coli, and K. oxytoca [40].
Efficacy of Carvacrol-Containing Essential Oils Against Gram-Positive, Gram-Negative, and Antibiotic-Resistant Bacterial Strains
Carvacrol is a key antibacterial constituent in numerous plant essential oils (EOs), with its abundance varying widely across species and cultivars. Its presence and concentration are closely linked to the antibacterial efficacy of the EOs, with synergistic interactions often observed between carvacrol and other EO components (e.g., p-cymene, γ-terpinene, borneol) that enhance its activity [38][41][2]. High antibacterial properties of natural extracts are frequently attributed to their carvacrol and thymol content, with Zataria multiflora EO’s activity explicitly linked to these two compounds [42][43][44]. The hydroxyl group in carvacrol’s phenolic structure is fundamental to its antimicrobial effectiveness, explaining its stronger activity compared to non-phenolic compounds, while the position of this group influences efficacy against specific Gram-negative strains [36]. Carvacrol’s mechanism of action involves disrupting bacterial cell membranes (including the lipopolysaccharide outer layer of Gram-negative strains), increasing permeability to ATP, and disrupting the proton motive force, ultimately inhibiting growth [38][2][4].
Carvacrol Content in Plant Essential Oils
| Plant Source | Carvacrol Content | Citation(s) |
|---|---|---|
| Oregano EO | 81.85% | [1] |
| Thyme EO | 12.42% | [1] |
| Satureja montana EO | 825.0–950.0 μg/mg | [45] |
| Greek oregano EO | 37.21% | [4] |
| Spanish oregano EO | 42.0% | [2] |
| Savoury EO | 32.8% | [2] |
| Greek oregano EO | 72.0% | [2] |
| Origanum vulgare cultivars ‘Hirtum’, ‘Margarita’, ‘Hot & Spicy’; Origanum syriacum EOs | 58–86% (relative percentages) | [10] |
| Oregano EO | 91.6% | [13] |
| Origanum vulgare EO | 14.5% | [15] |
| Wild oregano EOs (Samothraki, Skopelos, Nafpaktia, Greece) | 63.14–82.76% | [46] |
| Thymus zygis EO | 75.6% | [17] |
| Zataria multiflora EO (SC-CO₂ extraction) | 21.37 wt.% | [44] |
| Satureja montana L. EO | 11.07% | [47] |
| Thymus capitatus EO (Group A’) | 56.1 ± 3.0% (among monoterpene phenols: 1.02 ± 0.4–56.6 ± 2.8%) | [48] |
| TpC EO | 25.43% | [49] |
| Lavandula micromera leaf EO | 22.0% | [19] |
| Plectranthus amboinicus leaf EO | 51.3% | [19] |
| Satureja macrantha EO (Kaleybar population) | 48.6% | [20] |
| Satureja macrantha EO (Marand population) | 41.5% | [20] |
| Achillea debrana root EO | 4.15% | [21] |
| Achillea tenuifolia EOs (vegetative stage) | 33.19% | [23] |
| Achillea tenuifolia EOs (flowering stage) | 34.11% | [23] |
| Achillea tenuifolia EOs (fruiting stage) | 30.85% | [23] |
| Greek oregano EO | 84.4% | [24] |
| Satureja montana EO | 306 g L⁻¹ | [25] |
| Thymus vulgaris L. EO | 4.62% | [26] |
| Thyme EO | 75.27% | [27] |
| Oregano EO | 72.9% | [28] |
| Population ‘II’ EO | 64.6% | [33] |
| Supplier A EO | 10.61/3.84% | [50] |
| Supplier B EO | 10.85/5.59% | [50] |
| Supplier C EO | 10.92/3.60% | [50] |
Carvacrol-containing EOs demonstrate efficacy against both Gram-positive and Gram-negative bacterial strains, though Gram-positive strains (e.g., Staphylococcus aureus) often show larger inhibition zones due to the protective lipopolysaccharide layer of Gram-negative strains [38]. However, carvacrol disrupts this layer, enhancing its activity against Gram-negative pathogens [51][4]. For example, Greek oregano EO (high carvacrol) inhibits Escherichia coli and E. coli O157:H7 with MIC values of 0.25–1 mg mL⁻¹ [4], while Spanish oregano, savoury, and Greek oregano EOs (high carvacrol) exhibit IC₅₀ concentrations of 26–88 μg mL⁻¹ against all tested pathogens [2]. Variability in sensitivity exists: Achillea tenuifolia EOs are ineffective against Pseudomonas aeruginosa [23], while Satureja montana L. EO inhibits E. coli more effectively than S. aureus [47]. Vapor-phase carvacrol also significantly inhibits both Gram types [36].
Against antibiotic-resistant strains, carvacrol-containing EOs show promising synergistic interactions with conventional antibiotics. Thymus maroccanus EO (76.35% carvacrol) synergizes with ciprofloxacin, gentamicin, and pristinamycin [45], while Thymus saturejoides EOs (25.3–45.3% carvacrol) work synergistically with cefixime against Klebsiella pneumoniae [45]. These synergies arise from carvacrol targeting bacterial membranes, enzymes, ATP, and DNA, complementing the cell wall or protein targets of antibiotics [45]. Carvacrol associations also synergize against Enterobacter aerogenes and E. coli [51]. EOs with high carvacrol content (e.g., Origanum vulgare cultivars, oregano EO with 91.6% carvacrol) exhibit low MICs against MRSA and multi-drug resistant (MDR) Enterobacteriaceae [10][52][53], though some EOs (e.g., Lavandula micromera) are less effective against MRSA [19].
Carvacrol-containing EOs also exhibit significant anti-biofilm activity. High-carvacrol EOs (e.g., LOT, LOC) inhibit biofilm formation by over 70% in E. coli and MRSA, with LOC EO altering bacterial morphology and preventing biofilm development [54]. Origanum vulgare EO inhibits S. pyogenes biofilm formation in a concentration-dependent manner, with 0.5 mg/mL as the minimum biofilm inhibitory concentration (MBIC) [13]. All tested EOs (including carvacrol-rich ones) inhibit S. aureus biofilm formation by ~95% at half their MIC [53], though Satureja hortensis L. EO has limited anti-biofilm activity at subinhibitory concentrations [12].
In practical applications, carvacrol-containing EOs extend food shelf life by inhibiting bacterial growth. Rainbow trout fillets wrapped in quinoa starch-based film with 2% oregano EO (high carvacrol) have a shelf life of 15–18 days (vs. 7–9 days for controls) [1], while thyme EO (high carvacrol) reduces Salmonella typhimurium counts in minced meat stored at 4°C [27]. The phenological stage of plants also influences efficacy: Achillea tenuifolia EOs from vegetative and flowering stages have better antibacterial activity than those from the fruiting stage [23], highlighting the importance of harvest timing for optimal therapeutic properties.
Mechanisms of Bacterial Growth Inhibition by Carvacrol, Including Membrane Disruption and Anti-Biofilm Activity
Carvacrol is a key antibacterial constituent in plant essential oils (EOs), often identified as the most abundant component in EOs from species like Origanum compactum, Thymbra spicata var. spicata, and Satureja hortensis L. [38][41][6][12]. Its antimicrobial activity is primarily attributed to its phenolic structure, where the hydroxyl group and its position are fundamental for effectiveness [38]. Carvacrol exerts bacteriostatic and bactericidal effects by disrupting bacterial membrane integrity: it disturbs the outer membrane of Gram-negative bacteria, releasing lipopolysaccharides, and increases cytoplasmic membrane permeability, leading to ATP leakage and proton motive force disruption [51][41][6][4]. For example, incubation of Bacillus subtilis with Origanum compactum EO (rich in carvacrol) caused culture broth color change due to increased membrane permeability and H+ release [41]. Gram-positive bacteria typically show larger inhibition zones than Gram-negative bacteria, as the latter’s lipopolysaccharide outer membrane restricts diffusion of hydrophobic compounds like carvacrol [38]. However, carvacrol can disintegrate the extrinsic membrane of Gram-negative bacteria, overcoming this resistance [38].
Synergistic interactions enhance carvacrol’s efficacy: p-cymene, a common co-component in carvacrol-rich EOs, swells bacterial cell membranes to facilitate carvacrol entry [38], and associations with carvacrol are synergistic against Enterobacter aerogenes and Escherichia coli [51]. Borneol also acts synergistically with carvacrol and thymol to increase bacterial growth inhibition [41]. Carvacrol-rich EOs demonstrate potent antibacterial activity against a range of pathogens, with specific efficacy data summarized below:
Antibacterial Efficacy of Carvacrol-Rich Essential Oils Against Pathogenic Bacteria
| Source of EO (Carvacrol Content) | Target Bacteria | Key Efficacy Metric | Reference |
|---|---|---|---|
| Greek oregano EO (37.21% carvacrol) | E. coli, Salmonella enteritidis, Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus | MIC values: 0.25–1 mg/mL | [4] |
| Lippia origanoides thymol–carvacrol (LTC II) EO | Tested strains | MIC50: 0.45 mg/mL; MBC: 0.75 mg/mL | [55] |
| S. hortensis L. EO (major component carvacrol) | All tested bacteria | Inhibition at 0.125 μL/mL | [12] |
| Oregano EO (91.6% carvacrol) | Streptococcus pyogenes | 99.9% inoculum elimination at 0.5 mg/mL (5 min) | [13] |
Beyond planktonic growth inhibition, carvacrol contributes to anti-biofilm activity. Specific anti-biofilm effects of carvacrol-rich EOs are detailed below:
Anti-Biofilm Activity of Carvacrol-Rich Essential Oils
| Source of EO (Carvacrol Content) | Target Bacteria/Strains | Key Anti-Biofilm Effect | Reference |
|---|---|---|---|
| LTC II EO | S. aureus ATCC 29213; E. coli ATCC | Biofilm formation inhibition: 71% (S. aureus); 76% (E. coli) | [55] |
| Origanum vulgare cultivars ‘Hirtum’, ‘Margarita’, ‘Hot & Spicy’ EO (58–86% carvacrol) | Tested bacteria | Prevented mature biofilm formation (treated bacteria remained discrete) | [10] |
| Oregano EO (91.6% carvacrol) | Streptococcus pyogenes | Concentration-dependent biofilm reduction; MBIC: 0.5 mg/mL | [13] |
| Thymbra capitata EO (43.9% carvacrol) | Tested strains | Biofilm production inhibition at subinhibitory concentrations (1/4 to 1/8 MIC) | [39] |
| Thymus vulgaris carvacrol chemotype EO (44.66% carvacrol) | Streptococcus mutans | Antibacterial activity (phenols including carvacrol correlated with inhibition zone sizes) | [16] |
Carvacrol also interacts with bacterial proteins involved in biofilm formation, such as gbpB, gtfB, gtfC, and spaP, via stable binding at specific pockets [16].
Correlation Between Carvacrol Content Variability (Chemotypes, Extraction Methods, Phenological Stages) and Antibacterial Efficacy
Carvacrol is a key antibacterial constituent in plant essential oils (EOs), with its content variability across chemotypes, extraction methods, environmental conditions, geographic origins, and phenological stages directly correlating with antibacterial efficacy. Among Thymus species, carvacrol content ranges widely, forming a distinct high-carvacrol subgroup (20.19–42.14%) alongside three broader chemotypes: high thymol, geraniol/linalool, and high carvacrol [3]. A negative correlation (-0.597*) between thymol and carvacrol supports this chemotype classification [3]. Variability in carvacrol content and its associated antibacterial activity is further shaped by extraction methods, environmental stressors, and species-specific traits, as detailed below.
Carvacrol Content Variability Across Plant Species, Extraction Methods, and Phenological Stages
| Plant Species/Accession | Carvacrol Content (%) | Context | Citation |
|---|---|---|---|
| T. carmanicus | 42.14 | Maximum among Thymus species | [3] |
| T. fedtschenkoi-1 | 38.52 | High-carvacrol Thymus accession | [3] |
| T. transcaspicus | 37.11 | High-carvacrol Thymus accession | [3] |
| T. spicata var. spicata (SFME) | 44.8 | Supercritical fluid microwave extraction | [6] |
| T. spicata var. spicata (HD) | 36.1 | Hydrodistillation | [6] |
| Summer savory (HD) | 48.7 | Hydrodistillation | [5] |
| Summer savory (MAHD) | 47.7 | Microwave-assisted hydrodistillation | [5] |
| S. hortensis (Kahnuj, NaCl-stressed) | 8.38 | Increased under salinity stress | [56] |
| S. hortensis (Bardsir, NaCl-stressed) | (36% reduction) | Decreased under salinity stress | [56] |
| O. vulgare subsp. hirtum (Skopelos) | 82.76 | Highest among Greek populations | [46] |
| O. vulgare subsp. hirtum (Samothraki) | 63.14 | Greek carvacrol-type population | [46] |
| O. vulgare subsp. hirtum (Nafpaktia) | (Range: 63.14–82.76) | Greek carvacrol-type populations | [46] |
| Wild O. vulgare subsp. hirtum (Turkey) | 7.5–82.9 | Marmara region populations | [18] |
| Cultivated O. vulgare subsp. hirtum (Turkey) | 5.3–85.4 | Marmara region populations | [18] |
| Cluster analysis Group II | Up to 96.7 | 527-sample dataset | [31] |
| Population I (unspecified species) | 9.9 | Comparative population study | [33] |
| Population II (unspecified species) | 64.6 | Comparative population study | [33] |
| A. tenuifolia (vegetative) | 33.19 | Phenological stage | [23] |
| A. tenuifolia (flowering) | 34.11 | Phenological stage | [23] |
| A. tenuifolia (fruiting) | 30.85 | Phenological stage | [23] |
| O. vulgare subsp. glandulosum (early vegetative) | 61.08 | Phenological stage | [57] |
| O. vulgare subsp. glandulosum (fruiting) | 83.37 | Phenological stage | [57] |
| T. daenensis ecotypes | 5.14–51.89 | Ecotype variability | [8] |
| TEO4 (Thymus carvacrol chemotype) | 44.66 | Chemotype-specific EO | [16] |
| S. subspicata | 16.76 | EO with broad antibacterial activity | [11] |
EOs rich in carvacrol exhibit potent antibacterial activity, with efficacy varying by carvacrol concentration, target pathogen, and synergistic interactions with antibiotics. For example, Thymus high-carvacrol EOs sometimes match control antibiotic efficacy, while sage EO (0.69% carvacrol) shows the lowest activity [34]. Oregano EO with 91.6% carvacrol eliminates 99.9% of S. pyogenes within 5 minutes at 0.5 mg/mL [13], and S. subspicata EO (16.76% carvacrol) inhibits 13 bacterial species, with Gram-positive S. aureus being most sensitive (28–34 mm inhibition zones) [11]. Thymus daenensis ecotypes with higher carvacrol (5.14–51.89%) display varying potency, with TD5, TD3, and TD10 most active against S. aureus and B. subtilis [8].
The antibacterial mechanism of carvacrol involves disrupting bacterial membrane integrity—observed as cell size reduction, deformed structures, and ruptured cells in S. pyogenes treated with oregano EO [6][13]. It also inhibits biofilm formation: high-carvacrol oregano EO reduces MRSA biofilm by 70% and prevents E. coli biofilm development, with SEM showing lysed bacteria and disrupted extracellular matrix [54][10]. In Thymus carvacrol chemotype EO (TEO4, 44.66% carvacrol), MIC values against S. mutans are 1.25 μL/mL, with carvacrol interacting strongly with bacterial proteins brpA and gbpB [16]. Additionally, carvacrol-rich EOs synergize with antibiotics: Satureja hortensis EO (SEO) at 1/4 MIC reduces gentamicin MIC against E. coli and L. monocytogenes, with FIC indices ≤0.5 [39].
Consistent correlations between carvacrol content and efficacy confirm its role as a primary driver of antimicrobial potential. Greek carvacrol-type O. vulgare subsp. hirtum EOs completely inhibit four pathogens, with Gram-positive bacteria (S. aureus > B. cereus) more susceptible than Gram-negative (S. Typhimurium > E. coli) [46]. A. tenuifolia EOs from vegetative/flowering stages (higher carvacrol) have greater activity than fruiting-stage EOs (lower carvacrol) [23], and O. vulgare subsp. glandulosum fruiting-stage EO (83.37% carvacrol) shows larger inhibition zones (23 mm vs. 18 mm) against E. coli than early vegetative-stage EO (61.08% carvacrol) [57]. Population II (64.6% carvacrol) also has stronger activity against S. aureus and E. aerogenes (MIC 1/3200) than Population I (9.9% carvacrol) [33]. PCA of T. serpyllum and T. vulgaris EOs links carvacrol presence to stronger activity against Streptococcus spp., E. coli, and E. sakazakii [40], while S. macrantha EOs from Kaleybar (48.6% carvacrol) and Marand (41.5% carvacrol) have MICs of 4.69–37.50 µg/mL against four strains, with Marand EO (41.5% carvacrol) showing the highest activity [20].
Synergistic Effects of Carvacrol with Other Essential Oil Components and Antibiotics on Bacterial Inhibition
Carvacrol is a key antibacterial constituent in essential oils (EOs) from multiple plant species, with its abundance varying across sources. Its antibacterial efficacy spans diverse pathogens, and it exerts antimicrobial effects through membrane disruption and interactions involving its phenolic hydroxyl group. Synergistic combinations with other EO components and antibiotics further enhance its bacterial inhibition, with synergism often correlating with carvacrol content.
Carvacrol Abundance in Plant-Derived Essential Oils
| Plant Species/Essential Oil Source | Carvacrol Abundance | Citation |
|---|---|---|
| Satureja montana | 825.0–950.0 μg/mg | [45] |
| Thymus maroccanus | 76.35% | [45] |
| Thymus saturejoides | 25.3–45.3% | [45] |
| Origanum compactum | Not specified (component present) | [41] |
| EO with carvacrol as most abundant component | 43.9% | [39] |
Antibacterial Efficacy of Carvacrol Against Pathogens
| Target Pathogen(s) | Efficacy Outcome | Citation |
|---|---|---|
| 15 Salmonella enterica subsp. serovar Heidelberg strains | Entirely suppressed growth | [45] |
| Salmonella enterica sv Anatum SF2 | Minimum inhibitory concentration (MIC) = 250 μg/mL | [45] |
| Fusobacterium nucleatum, Porphyromonas gingivalis (planktonic cells) | Strong activity; better efficacy than p-cymene and phellandrene | [35] |
| Staphylococcus aureus | MIC = 1.38 mg/mL, Minimum bactericidal concentration (MBC) = 2.77 mg/mL | [58] |
| Streptococcus dysgalactiae | MIC = 0.05 mg/mL, MBC = 0.11 mg/mL | [58] |
Against Gram-negative bacteria, carvacrol’s hydrophobic nature disturbs the outer membrane, releases lipopolysaccharides, increases cytoplasmic membrane permeability to ATP [51], and enhances H+ release into culture media (evidenced by broth color changes in Bacillus subtilis cultures) [41]. Its phenolic hydroxyl group is fundamental to this antimicrobial activity, explaining greater efficacy compared to non-phenolic components [38].
Synergistic effects of carvacrol with other EO components and antibiotics enhance bacterial inhibition. Pairwise combinations of carvacrol with p-cymene and phellandrene from an EO showed synergistic inhibition of F. nucleatum and additive effects on P. gingivalis [35]. p-Cymene specifically swells bacterial cell membranes, facilitating carvacrol entry [38], while borneol in Thymus satureioides acts synergistically with carvacrol and thymol in O. compactum to increase bacterial growth inhibition [41]. With antibiotics, Thymus maroccanus EO (high carvacrol content) demonstrated synergism with ciprofloxacin, gentamicin, and pristinamycin—attributed to carvacrol targeting membranes, enzymes, ATP, and DNA, alongside antibiotic actions on proteins or DNA [45]. Thymus saturejoides EOs (carvacrol-rich) synergized with cefixime against Klebsiella pneumoniae [45], and an EO with 43.9% carvacrol reduced gentamicin MICs for E. coli (to 1/16 MIC) and Listeria monocytogenes (FICI < 0.38) [39]. Additionally, EOs containing carvacrol (e.g., from Thymus species) synergized with tetracycline (Tc) to reduce Tc MICs from 256 μg/mL to 4 μg/mL against Salmonella enterica strains, with TSEO (high carvacrol) showing notable bioactivity in combination [59]. These synergistic interactions often correlate with carvacrol content: Thymus maroccanus EO (76.35% carvacrol) had broader antibiotic synergism than Thymus broussonetii EO (39.77% carvacrol) [45].
Molecular Mechanisms of Carvacrol-Mediated Bacterial Growth Inhibition
Carvacrol-Mediated Bacterial Membrane Disruption and Ion Leakage
Carvacrol’s hydrophobic nature enables it to disrupt the outer membrane of Gram-negative bacteria, releasing lipopolysaccharides and increasing cytoplasmic membrane permeability to ATP [60]. This membrane disruption is supported by electron microscopy and dye permeabilization assays across multiple bacterial species, with effects often concentration-dependent and linked to visible morphological damage. Synergistic interactions with other compounds, encapsulation strategies, and structural features (e.g., the hydroxyl group) further modulate its membrane-disrupting efficacy.
Carvacrol-Induced Morphological and Membrane Damage Across Bacterial Species
| Bacterial Species | Treatment Details | Observed Effects | Citation(s) |
|---|---|---|---|
| Listeria monocytogenes | Oregano oil (rich in carvacrol) | Morphological damage, disrupted membranes, increased dye permeabilization | [61] |
| L. monocytogenes | 0.020% (wt/vol) carvacrol (intermediate) | Irregular cell walls | [61] |
| L. monocytogenes | 0.025% (wt/vol) carvacrol (MIC) | Severe wall damage, deep dye penetration, muropeptide degradation | [61] |
| Escherichia coli | Carvacrol | Surface protrusions, morphological damage, nucleic acid/protein leakage | [62] |
| Staphylococcus pyogenes | ½ × MIC carvacrol | Significant cell death | [63] |
| S. pyogenes | Concentration-dependent carvacrol | Ruptured walls, detached cytoplasmic membranes, cytoplasmic dispersion | [63] |
| Pseudomonas aeruginosa | Carvacrol (biofilm cells) | Complete cell shrinkage, deflation, cell wall holes | [64] |
| Enterococcus faecalis | Carvacrol (biofilm cells) | Complete cell shrinkage, deflation, cell wall holes | [64] |
| P. fluorescens | Carvacrol | Wrinkled surfaces, punctuated holes, protoplasm reduction, membrane detachment | [65] |
| E. coli / Bacillus subtilis | Carvacrol | Diffuse membranes, cellular debris, flagella loss, nucleic acid leakage | [275, 230] |
| Staphylococcus epidermidis | Oregano essential oil (rich in carvacrol) | Wrinkled surfaces, partial membrane disintegration | [66] |
| Salmonella Typhimurium DT104 | 0.8 mM carvacrol (sub-lethal) | ATP leakage, membrane permeability to nucleotides | [67] |
| Xanthomonas campestris pv. campestris (Xcc) | 0.0195% carvacrol | Cytoplasmic membrane deformations, no viable cells after 1 h | [68] |
The hydroxyl group in carvacrol’s structure is critical for its membrane-disrupting activity; removal of this group (as in p-cymene) results in complete loss of antimicrobial activity [69][38][70]. Carvacrol interacts with phospholipid membranes by fluidizing the lipid bilayer, decreasing the phase transition temperature (Tm) of dimyristoylphosphatidylcholine (DMPC) liposomes—effects stronger than non-phenolic monoterpenes at higher molar fractions [71]. This fluidizing effect is concentration-dependent: carvacrol and thymol caused concentration-dependent carboxyfluorescein (CF) leakage from large unilamellar vesicles (LUVs), with greater dye release than p-cymene or γ-terpinene [71]. Carvacrol also depletes intracellular ATP pools by reducing synthesis and increasing hydrolysis, enhancing proton permeability and reducing transmembrane electric potential [72]. In Bacillus cereus, this leads to altered membrane potential and increased permeability to protons and K+ ions [73].
Concentration-dependence is a key feature of carvacrol’s activity: higher concentrations cause more severe damage (e.g., L. monocytogenes [61], S. pyogenes [63]) and can reduce growth rates in Salmonella strains [67]. Encapsulation enhances efficacy: encapsulated carvacrol (E-CARV) caused greater K+ leakage and GFP release in P. aeruginosa than free carvacrol (F-CARV), with a 4-fold lower MIC [64]. Carvacrol-loaded nanoparticles and nanofiber webs also disrupt membranes, as shown by live/dead staining and electron microscopy [275, 108].
Synergistic interactions further enhance carvacrol’s effects. Combinations with nisin improved γ-irradiation inactivation of B. cereus [74], while carvacrol/cinnamaldehyde mixtures showed synergism against E. coli and L. innocua [75]. For Xcc, carvacrol-thymol combinations yielded a synergistic FICI of 0.31 [68], and carvacrol-p-cymene combinations facilitate transport across B. cereus membranes [60]. Additive effects were noted for carvacrol-thymol against S. aureus and P. aeruginosa [76].
Synergistic Antibacterial Effects of Carvacrol with Co-Compounds and Formulations
Carvacrol exerts its antibacterial activity primarily through membrane disruption mechanisms: as a hydrophobic compound, it disturbs the outer membrane of Gram-negative bacteria, releasing lipopolysaccharides, and increases cytoplasmic membrane permeability to ATP [75][51][60]. The hydroxyl group in its phenolic structure is fundamental to this activity, explaining its greater efficacy compared to non-phenolic or hydroxyl-deficient compounds like p-cymene [38][70][77]. This membrane damage leads to leakage of intracellular contents (e.g., potassium, phosphate) and dissipation of pH gradients, as observed in Pseudomonas aeruginosa and Staphylococcus aureus [78], and can cause visible morphological deformations (e.g., wrinkling, collapse) in bacterial cells [79][80][68][81][65]. Specifically, carvacrol acts as a transmembrane monovalent cation (hydroxyl proton for a potassium cation) exchanger, further contributing to membrane dysfunction [77]. Beyond membrane effects, carvacrol induces rRNA degradation in Acinetobacter baumannii [82] and downregulates ribosomal subunit assembly genes in multidrug-resistant (MDR) A. baumannii [83], further inhibiting growth.
Carvacrol Synergistic Combinations and Their Effects
| Combination Pair | Target Organism(s) | Key Mechanism/Outcome | Citations |
|---|---|---|---|
| Carvacrol/cinnamaldehyde | E. coli, Listeria innocua, S. typhimurium | Optimal 1:0.1 ratio (MIC 0.55 mg/mL) against E. coli; membrane permeability enhancement or pore modulation for S. typhimurium | [75][84] |
| Carvacrol/eugenol | E. coli | 25% concentration reduction at 1:4 ratio; carvacrol facilitates eugenol cytoplasmic entry | [75][84] |
| Carvacrol/thymol | S. typhimurium, MDR A. baumannii, S. aureus, P. aeruginosa, X. campestris pv. campestris, B. subtilis | Synergism (FICI 0.5 with meropenem); efflux pump inhibition (with tetracycline); non-cytotoxic to mammalian cells | [78][83][84][85][81] |
| Carvacrol/p-cymene | B. cereus | p-cymene swells membranes to enhance carvacrol penetration | [77][84][86][60] |
| Carvacrol/borneol | Bacteria (unspecified) | Enhanced membrane disruption | [41] |
| Carvacrol/doxycycline | Bacterial targets (unspecified) | Synergistic activity | [85] |
| Carvacrol/meropenem | Clinical bacterial strains | Fourfold reduction in meropenem MIC (FICI 0.5) | [79] |
| Carvacrol/nisin + γ-irradiation | Bacillus cereus | 1.5-fold greater reduction in viable cells than carvacrol alone | [74] |
Formulations enhance carvacrol’s efficacy: polythioether nanoparticles loaded with thymol/carvacrol (TC NPs) show higher antimicrobial activity than pure carvacrol-loaded NPs (C NPs), inhibiting growth of antibiotic-resistant species like S. aureus and B. cenocepacia [81]. TC NPs cause cell envelope damage (diffuse membranes, cellular debris) and pore-like lesions in B. subtilis, consistent with membrane targeting [81]. Carvacrol-loaded chitosan nanoparticles (Th-CNPs) reduce MIC values by 17–67-fold compared to pure thyme essential oil (e.g., 0.03 mg/mL for L. monocytogenes vs. 1 mg/mL for pure EO) [70], while microencapsulation improves solubility and bioavailability, boosting growth inhibition [76]. Oregano essential oil (OEO)-loaded SMV formulations exhibit lower MIC values (0.64 mg/mL) than free OEO (1.28 mg/mL) against E. coli and S. epidermidis, with sustained bactericidal activity over 72 h and visible membrane damage [66]. Additionally, carvacrol/thymol combinations with low-temperature storage (0 to 3 °C) optimize antibacterial effects in poultry patties [84]. Notably, carvacrol combinations (e.g., with thymol) against MDR A. baumannii remain non-cytotoxic to mammalian cells [83], supporting their potential for therapeutic and food safety applications.
Carvacrol’s Inhibition of Bacterial Virulence Factors and Biofilm Formation
Carvacrol exhibits potent inhibition of bacterial virulence factors and biofilm formation across diverse pathogens, with mechanisms linked to membrane disruption, metabolic interference, and direct interaction with virulence-related proteins. Its biofilm-inhibitory and eradicative effects vary by pathogen, carvacrol formulation, and concentration, as summarized below:
Carvacrol-Mediated Biofilm Inhibition and Eradication Across Pathogens
| Pathogen | Carvacrol Type/Source | Concentration | Effect | Citations |
|---|---|---|---|---|
| Pseudomonas aeruginosa | Free carvacrol (F-CARV) | Minimum inhibitory concentration (MIC) | 4.8 log CFU/mL reduction in preformed biofilm after 15 minutes | [64] |
| Pseudomonas aeruginosa | Encapsulated carvacrol (E-CARV) | MIC | Near-complete cell death in preformed biofilm after 15 minutes; higher K⁺ leakage than F-CARV | [64] |
| Pseudomonas aeruginosa | Pure carvacrol | N/A | Reduced biofilm formation on stainless steel surfaces | [87][64] |
| Salmonella enterica serovar Typhimurium | Carvacrol + thymol | N/A | Decreased biofilm mass | [87][88] |
| Enterococcus faecalis | E-CARV | MIC | 5.5 log CFU/mL reduction in preformed biofilm after 15 minutes | [64] |
| Staphylococcus aureus | Pure carvacrol | 0.5 mg/mL (sub-MBC); 1 mg/mL (MBC) | 3 logs reduction in preformed biofilm at 0.5 mg/mL; >5 logs reduction at 1 mg/mL | [80] |
| Escherichia coli | Pure carvacrol | 0.5 mg/mL (sub-MBC); 1 mg/mL (MBC) | 3 logs reduction in preformed biofilm at 0.5 mg/mL; >5 logs reduction at 1 mg/mL | [80] |
| Streptococcus pyogenes | Oregano essential oil (91.6% carvacrol) | 0.5 mg/mL (minimum biofilm inhibitory concentration, MBIC) | Inhibits biofilm formation (concentration-dependent); eradicates one-day-old preformed biofilms | [13] |
| Klebsiella pneumoniae | Carvacrol-rich essential oil (ASHEO) | 0.015 mg/mL (sub-MIC) | 72.8% reduction in biofilm formation | [89] |
| Acinetobacter baumannii | ASHEO | 0.015 mg/mL (sub-MIC) | 64.15% reduction in biofilm formation | [89] |
| E. coli | ASHEO | 0.015 mg/mL (sub-MIC) | 52.08% reduction in biofilm formation | [89] |
| Streptococcus mutans | Pure carvacrol | 10× MIC | Rapid elimination of mature biofilms; reduced intracellular ATP; morphological changes (cell deformation, vesicular formation) | [90] |
| Streptococcus sanguinis | Pure carvacrol | 10× MIC | Rapid elimination of mature biofilms | [90] |
Beyond biofilms, carvacrol suppresses key virulence factors including motility, invasion, and hemolysis. Salmonella Typhimurium DT104 shows reduced motility at 0.4 mM carvacrol and complete abolition at 1 mM—without flagellar loss, indicating impaired function rather than structure [67]. Invasion of IPEC-J2 and Caco-2 cells by S. Typhimurium is reduced to 34% and 14% of controls at 0.5 mM and 0.8 mM carvacrol, respectively, with no significant adhesion effects at lower concentrations [67]. Lippia origanoides essential oil (high in carvacrol) reduces S. aureus hemolytic activity by 54% and inhibits E. coli swimming motility by 55% at subinhibitory concentrations [55]. Molecular docking studies reveal carvacrol binds to critical virulence-related enzymes: polyketide synthase (aflatoxin biosynthesis) with -7.0 kcal/mol binding energy and enzyme 2ZDQ (cell wall/protein biosynthesis) with -8.1 kcal/mol, via hydrogen bonding, π-anion, and hydrophobic interactions [89]. Against S. mutans, it interacts with virulence proteins brpA (-5.8 kcal/mol), gbpB, and spaP (-5.7 kcal/mol), disrupting adhesion and biofilm pathways [16]. Additionally, carvacrol downregulates virulence gene expression (e.g., faeG) in enterotoxigenic E. coli, though eugenol has no effect on faeG [91].
The mechanisms underlying these effects center on membrane disruption, evidenced by potassium ion leakage and cytoplasmic content release. P. aeruginosa and E. faecalis exposed to carvacrol show immediate extracellular K⁺ increases within 30 seconds, with E-CARV inducing higher leakage in P. aeruginosa than F-CARV [64]. P. aeruginosa GFP strains treated with carvacrol exhibit 6.5-fold higher extracellular GFP fluorescence after 40 minutes, indicating membrane damage and cytoplasmic protein leakage [64]. In S. aureus and E. coli, carvacrol at MBC causes membrane disruption, confirmed by flow cytometry (peaks matching chlorhexidine-induced damage) and confocal microscopy (propidium iodide staining for membrane compromise) [80]. SEM analysis of carvacrol-treated biofilm cells shows P. aeruginosa shrinkage/deflation and E. faecalis cell wall holes/deformation, confirming structural damage [64]. For S. pyogenes, carvacrol reduces cell surface hydrophobicity, contributing to biofilm inhibition [90]. These multi-targeted actions—disrupting membranes, interfering with virulence protein function, and modulating gene expression—make carvacrol a promising agent for controlling bacterial virulence and biofilm-related infections.
Mechanisms of Carvacrol Resistance Development in Bacterial Strains
Adaptive laboratory evolution (ALE) has been used to investigate carvacrol resistance development in Salmonella Typhimurium and Escherichia coli, revealing species-specific resistance profiles, genetic drivers, and associated phenotypic traits.
Carvacrol MIC Values of Wild-Type and Evolved Bacterial Strains
| Species/Strain | Carvacrol MIC (μL/L) | Reference(s) |
|---|---|---|
| S. Typhimurium SeWT (wild-type) | 133 | [92] |
| S. Typhimurium SeCarA (evolved lineage A) | 200 | [92] |
| S. Typhimurium SeCarB (evolved lineage B) | 350 | [92] |
| S. Typhimurium Selon (lon mutation) | 300 | [92] |
| S. Typhimurium Serob (rob mutation) | 350 | [92] |
| E. coli MG1655 WT (wild-type) | 200 | [93][94] |
| E. coli CAR (evolved) | 600 | [93][94] |
| E. coli BC010 (soxR reverted) | 200 | [93] |
In S. Typhimurium, 10 days of carvacrol ALE produced four lineages with variable resistance: SeCarA (50% MIC increase), SeCarB (highest resistance), and lineages C/D (no resistance) [92]. Genetic analysis linked single nucleotide variations (SNVs) in lon (ATP-dependent serine Lon protease) and rob (transcriptional regulator) to resistance: single-mutation constructs Selon and Serob matched the MICs of SeCarA and SeCarB, respectively [92]. All evolved S. Typhimurium strains also tolerated lethal carvacrol (150 μL/L) treatments, with only ~2.5 log₁₀ inactivation after 25 min compared to >5.5 log₁₀ for SeWT [92].
For E. coli MG1655, 10-day carvacrol ALE selected the CAR strain, with a missense mutation in soxR (superoxide response regulator) confirmed as the resistance driver via allelic reversion (strain BC010) [93]. The CAR strain showed cross-resistance to citral and (+)-limonene oxide (2 log₁₀ inactivation vs. 5 log₁₀ for WT under lethal treatments) [94], but higher sensitivity to acute carvacrol (200 μL/L) at 2–5 min [93].
Cross-resistance to antibiotics was observed in both species: S. Typhimurium SeCarA had 2-fold higher ampicillin/chloramphenicol MICs, while SeCarB was cross-resistant to most tested antibiotics (except cephalexin/kanamycin) [92]; E. coli CAR showed increased resistance to ampicillin, trimethoprim, chloramphenicol, and tetracycline, linked to the soxR mutation [93]. Fitness costs were associated with resistance: E. coli CAR had lower late-stationary cell counts (≤1×10⁹ CFU/mL vs. 2×10⁹ CFU/mL for WT) and reduced co-culture fitness (improved in sub-MIC carvacrol) [94], while evolved S. Typhimurium strains (SeCarA/SeCarB) had shorter lag phases and faster growth rates in carvacrol-containing media [92].
Carvacrol’s Efficacy in Targeted Applications (Food Preservation, Animal Feed, and Surface Disinfection)
Carvacrol exerts antibacterial activity through multiple molecular mechanisms centered on bacterial cell membranes and stress responses. Its hydrophobicity drives accumulation in cell membranes, causing permeabilization, disruption of the proton motive force, and leakage of intracellular contents (potassium ions, nucleic acids, proteins) [6][95][80][63][64][72]. For instance, Pseudomonas aeruginosa and Enterococcus faecalis exhibited rapid potassium leakage within 30 seconds of carvacrol exposure, with stable extracellular potassium levels after 5 minutes [64]. In Acinetobacter baumannii, carvacrol induced rRNA degradation within 30 minutes (a effect not seen with cinnamaldehyde) and triggered extreme upregulation of heat shock protein (HSP) genes (e.g., 60-fold overexpression of clpB) and oxidative stress genes (e.g., 15-fold upregulation of katE) after 0.5 hours [82]. The hydroxyl group and delocalized electrons are critical for membrane-disrupting effects [87]. Additionally, carvacrol increases cell membrane permeability, reduces cytoplasmic pH gradients, inhibits ATP synthesis, and modifies lipid monolayers by forming antimicrobial−lipid complexes, reducing packing effectiveness, increasing fluidity, and altering dipole moments [96][73]. Against Gram-negative bacteria, it acts on outer membranes to release lipopolysaccharides, depolarize membranes, and inactivate enzymes via hydrogen bonding with active sites [97], while also decreasing respiratory activity in Listeria monocytogenes [98]. Synergism with p-cymene enhances efficacy by swelling membranes to facilitate carvacrol penetration [84][60], and electron microscopy of carvacrol-loaded nanoparticle-treated bacteria confirms cell envelope damage, diffuse membranes, debris, and pore-like lesions [81].
The antibacterial efficacy of carvacrol is concentration- and time-dependent, with minimal inhibitory concentrations (MICs) varying across bacterial strains. Time-kill assays show bacteriostatic activity against A. baumannii at 3 hours and bactericidal activity from 6–24 hours [82], while 2× MIC (250 µg/mL) achieved immediate complete killing of Staphylococcus pyogenes [63]. A 0.0195% carvacrol solution was bactericidal against Xanthomonas campestris pv. campestris within 30 minutes [68]. Encapsulated carvacrol also shows improved efficacy, with lower bacterial inhibition concentrations (BICs) than free carvacrol [98].
Carvacrol and Carvacrol-Containing Essential Oil (EO) Antibacterial Efficacy Metrics
| Bacterial Strain | Metric | Value | Citation |
|---|---|---|---|
| Staphylococcus pyogenes | MIC | 125 µg/mL | [63] |
| Xanthomonas campestris pv. campestris | MIC | 0.0098–0.0195% | [68] |
| Acinetobacter baumannii | MIC | 0.16–0.31 mg/mL | [82] |
| Shigella sonnei | MIC | 0.1−1.0% | [73] |
| Shigella flexneri | MIC | 0.1−1.0% | [73] |
| Mycobacterium avium subsp. paratuberculosis | MIC | 72.2 μg/mL | [97] |
| Escherichia coli | MIC | 65 µg·mL⁻¹ | [73] |
| Staphylococcus aureus | MIC | 36 µg·mL⁻¹ | [73] |
| Clostridium perfringens | MIC | 18 µg·mL⁻¹ | [73] |
| Pathogens (general) | MIC (SMEO, 53.58% carvacrol) | 0.44–3.55 µL/mL | [96] |
| Escherichia coli | Inhibition (EO, 91.56% carvacrol) | 0.05% v/v | [99] |
| Salmonella enterica | Inhibition (EO, 91.56% carvacrol) | 0.05% v/v | [99] |
| Salmonella enterica | BIC (chia nanoparticles, encapsulated carvacrol) | 0.42 mg/mL | [98] |
| Salmonella enterica | BIC (free carvacrol) | 1.77 mg/mL | [98] |
Carvacrol shows promise in targeted applications, particularly food preservation, where incorporation into biodegradable films or microcapsules enhances stability and efficacy. Chitosan films with carvacrol inhibited Bacillus subtilis, E. coli, Listeria innocua, and Salmonella Enteritidis, with the highest vapour concentration (1.08 × 10⁻⁷ g mL⁻¹) completely inhibiting just-inoculated bacteria [95]. Sodium and calcium caseinate films containing carvacrol targeted S. aureus and E. coli, with larger inhibition zones for S. aureus due to Gram-positive sensitivity [100]. Encapsulated carvacrol (E-CARV) reduced P. aeruginosa biofilm biomass by >99% at MIC within 15 minutes (vs. 4.8 log CFU/mL reduction for free carvacrol [F-CARV]) [64], and carvacrol-containing edible films inactivated E. coli, Salmonella, and L. monocytogenes on chicken breast, ham, and lettuce [73]. SMEO (high carvacrol) reduced Salmonella enterica serovar Typhimurium growth in fresh pork sausage at 0.075–0.150 µL/g [96].
In animal feed, carvacrol supplementation improves broiler meat quality via lipid oxidation inhibition [87], increases body weight by 2.64% vs. antibiotic controls [97], and inhibits Brachyspira intermedia in laying hens [73]. Blends with thymol and low temperatures (0–3 °C) enhance non-conventional poultry patty quality [84]. For surface disinfection, 10% carvacrol-loaded poly(lactic acid) (PLA) nanofiber webs inhibited over 92% of E. coli and S. epidermidis growth within 24 hours (complete E. coli inhibition within 2 hours) [101], while a 1% carvacrol-rich EO sanitizer achieved 5 log CFU/ml reductions of E. coli and S. enterica within 30 seconds [99]. Carvacrol vapor also eliminates S. enterica on raw chicken surfaces [73]. Synergistic combinations include meropenem (FICI = 0.5 against clinical strains [79]), nisin (enhances γ-irradiation efficacy against Bacillus cereus [74]), lauric alginate (reduces Salmonella in ground turkey by 4 log cfu/g [73]), and blends with cinnamaldehyde or eugenol (synergism against S. typhimurium [84][60]).
Antibacterial Efficacy of Carvacrol Against Diverse Bacterial Strains
Carvacrol Content in Plant Essential Oils and Correlated Antibacterial Efficacy
Carvacrol is a key phenolic monoterpene in essential oils (EOs) from diverse plant species, with concentrations varying widely across sources (see Table 1). This variability in carvacrol content correlates with the antibacterial efficacy of EOs: higher concentrations typically correspond to stronger activity against planktonic bacteria, resistant strains, and biofilms.
Carvacrol Concentrations in Essential Oils from Various Plant Sources
| Plant Source | Carvacrol Concentration | Reference |
|---|---|---|
| Greek oregano EOs | Up to 35.79% | [102] |
| M. didyma EO | 49.03% | [97] |
| SMEO | 53.58% | [96] |
| Carvacrol chemotype Origanum EOs | 58–86% | [10] |
| Wild oregano (O. minutiflorum) EO | 81.5% | [58] |
| EO6 | 91.56% | [99] |
| Oregano EO | 91.6% | [13] |
| S. thymbra EO | 29.2% | [14] |
| Unspecified EO | 43.9% | [39] |
| O. vulgare EO | 14.5% | [103] |
| T. vulgaris “carvacrol” type EO | 44.66% | [16] |
| Wild O. vulgare subsp hirtum EOs | 63.14–82.76% | [46] |
| Z. multiflora EO | 21.37% | [44] |
| S. montana EO | 11.07% | [47] |
| T. capitatus EO Group A’ | 56.1 ± 3.0% | [48] |
| L. micromera EO | 22.0% | [19] |
| P. amboinicus EO | 51.3% | [19] |
| Kaleybar S. macrantha EO | 48.6% | [20] |
| Marand S. macrantha EO | 41.5% | [20] |
| ZMEO | 30.50% | [104] |
| Oregano oil | 49.1% | [105] |
| A. tenuifolia EOs (vegetative stage) | 33.19% | [23] |
| A. tenuifolia EOs (flowering stage) | 34.11% | [23] |
| A. tenuifolia EOs (fruiting stage) | 30.85% | [23] |
| Carvacrol-dominated population EO | 64.6% | [33] |
| Thyme EO | 75.27% | [27] |
| O. vulgare subsp. glandulosum EO | 83.37% | [57] |
| Three EO samples (third most abundant) | 10.61–10.92% | [50] |
For example, Chemotype I of Z. multiflora EOs (higher carvacrol content) exhibited greater inhibitory activity against Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) than other chemotypes, with MIC values of 0.032 mg/ml against both strains—twice as strong as chloramphenicol against E. coli [106]. Similarly, EO6 (91.56% carvacrol) had the lowest MIC (0.05% v/v) against E. coli and S. enterica, with the widest inhibitory haloes [99]. Oregano EO with 91.6% carvacrol showed strong bactericidal activity against S. pyogenes, achieving 99.9% elimination of the initial inoculum after 5 minutes at 0.5 mg/mL [13]. S. thymbra EO (29.2% carvacrol) demonstrated concentration-dependent inhibition of L. monocytogenes and Salmonella Enteritidis: 0.1% (vol/vol) EO greatly inhibited growth initiation, especially at high salt contents and low temperatures, with greater effectiveness against Salmonella Enteritidis than L. monocytogenes [14]. An EO with 43.9% carvacrol showed MIC values of 0.39–0.78 mg/mL against S. aureus, 0.78–1.56 mg/mL against L. monocytogenes, and 1.56–3.12 mg/mL against uropathogenic E. coli [39]. T. vulgaris “carvacrol” type EO (44.66% carvacrol) had MIC and MBC values of 1.25 μL/mL and 5.0 μL/mL against S. mutans, respectively [16]. Wild O. vulgare subsp hirtum EOs (63.14–82.76% carvacrol) completely inhibited S. aureus, B. cereus, E. coli, and S. Typhimurium, with Gram-positive bacteria more susceptible than Gram-negative [46]. Z. multiflora EO (21.37% carvacrol) showed high antibacterial activity against E. coli and S. aureus, with viability not detected in samples with higher impregnation yields of the EO [44]. T. capitatus EO Group A’ (56.1 ± 3.0% carvacrol) was extremely active against E. coli, S. enterica, and P. aeruginosa (IZD 20.3 ± 0.6 mm) and very active against S. aureus (IZD 15.0 ± 1.0 mm), with MIC range 0.73–2.94 mg/mL [48]. L. micromera (22.0% carvacrol) and P. amboinicus (51.3% carvacrol) EOs had maximum activity against S. aureus and S. epidermidis (MIC 0.03–0.12%) but were least effective against MRSA (MIC 2.00%) [19]. Marand S. macrantha EO (41.5% carvacrol) had the highest antibacterial activity (MIC 4.69–18.75 µg/mL) among tested S. macrantha EOs [20]. ZMEO (30.50% carvacrol) showed antilisterial effects, with higher ZMEO concentrations causing greater L. monocytogenes population decreases [104]. A. tenuifolia EOs with higher carvacrol content in vegetative and flowering stages (33.19% and 34.11%, respectively) exhibited significantly higher antibacterial activities against Gram-positive and Gram-negative bacteria (except P. aeruginosa) compared to the fruiting stage (30.85% carvacrol) [23]. The essential oil of P. longiflora, with higher carvacrol content, exerted better antimicrobial activity than L. graveolens EO, with carvacrol more active than thymol and p-cymene against tested microorganisms [30]. S. montana EO, containing 306 g L−1 carvacrol, inhibited the growth of B. thermosphacta, L. innocua, L. monocytogenes, and P. putida with MIC values 0.80–2.10 µg mL−1 [25]. Thyme EO with 75.27% carvacrol had MIC values of 0.05% against S. aureus, E. coli O157:H7, and S. typhimurium [27]. O. vulgare subsp. glandulosum EO with 83.37% carvacrol at the flowering stage showed high antibacterial activity against E. coli and S. typhimurium with MIC values of 250 μg/mL [57]. The carvacrol-dominated population (64.6% carvacrol) showed significant activity against S. aureus and E. aerogenes (MIC: 1/3200) [33]. Principal components analysis (PCA) of Thymus EOs linked higher carvacrol content in T. vulgaris EO to stronger antibacterial potential against Streptococcus spp. (β-hemolytic), E. sakazakii, E. coli, and K. oxytoca [40]. The strong antibacterial action of OSS essential oils was attributed to carvacrol and thymol, with EOs showing lower or equal MIC values to carvacrol against tested bacterial strains [37]. SEO, with carvacrol as the major compound (14.3%), had higher antibacterial activity than WEO (thymol-dominated) against S. aureus, P. mirabilis, and K. pneumonia with MIC/MLC 0.125/0.25 μg/ml [29].
Carvacrol alone demonstrates potent antibacterial activity against planktonic cells of various pathogens. For F. nucleatum and P. gingivalis, carvacrol had the best activity among major ECO components, with slightly higher MIC than ECO itself, while p-cymene and phellandrene showed significantly lower activity [35]. Against E. coli and S. aureus, carvacrol in M. didyma EO had MIC values of 65 µg·mL⁻¹ and 36 µg·mL⁻¹, respectively, and was active against C. perfringens with an MIC of 18 µg·mL⁻¹ [97]. Its mechanism of action involves increasing cell membrane permeability, reducing the cytoplasmic membrane pH gradient, inhibiting ATP synthesis, and causing bacterial cell death [96]. Carvacrol and thymol can penetrate or disrupt lipid structures, affect the cytoplasmic membrane, damage its integrity, change motive power, and interfere with cell membrane sulfur-containing biomolecules, releasing lipopolysaccharides in Gram-positive bacteria [104]. Oregano oil and its phenolic components (including carvacrol) caused a rapid release of 260 nm absorbing material from E. coli and B. subtilis, with viable bacteria decreasing markedly at MIC concentrations [105]. Additionally, carvacrol contributes to EO activity against resistant strains: carvacrol-rich EOs (e.g., LOC EO) inhibited MRSA with MIC values of 0.6 mg/mL [54], and carvacrol chemotype Origanum EOs inhibited MRSA at 0.6 mg/mL [10].
Beyond planktonic cells, carvacrol-rich EOs exhibit antibiofilm activity. LOC EO, with high carvacrol content, reduced MRSA biofilm formation by 70% with an MIBC50 of 0.7 mg/mL and caused morphological changes (23% smaller cell size) and extracellular matrix disruption [54]. Oregano EO (91.6% carvacrol) inhibited S. pyogenes biofilm formation in a concentration-dependent manner, with an MBIC of 0.5 mg/mL, and caused cell debris accumulation and morphological changes (reduced cell size, ruptured structures) [13]. Wild oregano EO (81.5% carvacrol) inhibited S. aureus biofilm formation by 33.46% at MIC and destroyed 61.96% of preformed biofilm after 30 seconds [58]. Origanum EOs with high carvacrol prevented mature biofilm formation in Haemophilus strains, MRSA, and P. aeruginosa, though P. aeruginosa showed partial resistance [10]. An EO with 43.9% carvacrol, at 1/4 and 1/8 MIC, significantly inhibited biofilm production for all tested strains, with a dose-dependent reduction for L. monocytogenes [39].
Carvacrol’s Antibacterial Activity Against Diverse Bacterial Strains (Including Resistant Isolates)
Carvacrol exhibits broad-spectrum antibacterial efficacy against diverse Gram-negative and Gram-positive bacterial strains, including multidrug-resistant (MDR) isolates. Its activity spans reference strains, MDR pathogens, foodborne and oral pathogens, spoilage bacteria, and biofilm-forming isolates, with efficacy often enhanced by encapsulation, cocrystallization, or combination with other compounds. Carvacrol’s effects extend to practical applications in food preservation, agricultural settings, and antimicrobial coatings, with rapid bactericidal action observed against planktonic and biofilm-forming cells.
Carvacrol Antibacterial Activity: MIC, MBC, and Key Efficacy Data by Bacterial Strain/Context
| Bacterial Strain/Context | MIC/MBC/Activity Metric | Value | Citation(s) |
|---|---|---|---|
| Salmonella enterica serotype Typhimurium (ATCC 14028), Escherichia coli (ATCC 25922), Aeromonas hydrophila (ATCC 7966), Staphylococcus aureus (ATCC 25923) | MIC | 312 μg/ml | [107] |
| E. coli, Bacillus cereus | MIC | 0.2 mg/mL | [108] |
| Pseudomonas aeruginosa ATCC 9027 | MIC | 0.6 mL/mL | [109] |
| MDR strains (KPC-producing Klebsiella pneumoniae, carbapenem-resistant Acinetobacter baumannii, MRSA N315) | Mean MIC | 0.6 ± 0.3 mg/ml | [62] |
| Coagulase-negative staphylococci (CoNS) | Inhibitory concentration range | 1–2 mM | [110] |
| Listeria monocytogenes (fish fillets) | Inhibitory concentration | 0.5% (significantly lower counts vs. controls) | [111] |
| A. hydrophila, E. coli | Bactericidal concentration | 100 ppm, 200 ppm respectively | [112] |
| Brochothrix thermosphacta, Pseudomonas fragi | Bacteriostatic concentration | 100 ppm, 200 ppm respectively | [112] |
| Gram-negative vs. Gram-positive microorganisms | Activity type | Bactericidal (Gram-negative); bacteriostatic (Gram-positive) | [113] |
| S. aureus (ATCC 25923), E. coli (ATCC 25922) (carvacrol-rich essential oil chemotypes) | MIC | As low as 0.032 mg/ml | [106] |
| L. monocytogenes | Growth inhibition | 1.0 mmol/liter inhibits growth for ≥24 h (some strains) | [114] |
| L. monocytogenes (pH 4.0) | Inactivation | >5 log₁₀ cycles within 5 h (25 μl l⁻¹ carvacrol) | [115] |
| Aggregatibacter actinomycetemcomitans | MIC range | 0.16–0.31 mg/ml | [82] |
| Multi-resistant clinical strains (E. coli 128 MR, S. aureus 75 MR) | Complete inhibition time | 4 h (E. coli), 2 h (S. aureus) | [116] |
| Oral pathogens (Fusobacterium nucleatum, Porphyromonas gingivalis) | Activity | Effective | [35] |
| Salmonella Typhi | Sensitivity | Significantly reduced vs. thymol | [117] |
| E. coli | Inhibitory concentration | 1.5 mM | [118] |
| Shigella sonnei, S. flexneri | MIC range | 0.1–1.0% | [73] |
| Mycobacterium avium subsp. paratuberculosis | MIC | 72.2 μg/mL | [73] |
| Oral pathogen Streptococcus mutans | Activity | Effective | [73], [119] |
| Carbapenemase-producing Gram-negative bacilli | MIC range | 62–250 μg/mL | [120] |
| MRSA (carvacrol chemotype essential oils) | MIC | 0.6 mg/mL | [10] |
| Haemophilus influenzae, H. parainfluenzae | MIC | 0.15 mg/mL | [10] |
| Vegetable spoilage bacteria (15 strains) | Average MIC | 167 mg/ml | [121] |
| Listeria innocua (liquid culture, pH 7.0, aw 0.99) | MBC | 150 mg kg⁻¹ | [122] |
| Satureja hortensis L. essential oil (all tested strains) | Inhibitory concentration | 0.125 μl/ml | [12] |
| S. hortensis essential oil (54.069% carvacrol) | MIC range | 0.08–10.91 mg/mL | [123] |
| S. hortensis essential oil (Streptococcus sp. strains) | MIC range | 0.17–2.72 mg/mL | [123] |
| Oregano essential oil (91.6% carvacrol, S. pyogenes ATCC 19615) | MIC/MBC | 0.5 mg/mL (both); 99.9% elimination after 5 min | [13] |
| M. didyma essential oil (49.03% carvacrol) | MIC | 65 µg·mL⁻¹ (E. coli), 36 µg·mL⁻¹ (S. aureus), 18 µg·mL⁻¹ (C. perfringens) | [97] |
| O. minutiflorum essential oil (81.5% carvacrol) | MIC range | 0.03–1.38 mg/mL | [58] |
| S. hortensis essential oil (43.9% carvacrol) | MIC range | 0.39–0.78 mg/mL (S. aureus), 0.78–1.56 mg/mL (L. monocytogenes), 1.56–3.12 mg/mL (uropathogenic E. coli) | [39] |
| Mastitis pathogens (Staph. aureus, E. coli, Strep. uberis) | MIC/MBC range | 0.4–0.8% (MIC), 0.8–1.5% (MBC) | [124] |
| ASHEO (45.15% carvacrol) | MIC | 0.031 mg/mL (S. aureus, B. subtilis); 0.062 mg/mL (MRSA, E. coli); 0.125 mg/mL (P. aeruginosa, A. baumannii) | [89] |
| S. enterica, L. monocytogenes (encapsulated carvacrol) | BIC | Lower than free carvacrol | [98] |
| S. aureus IS-58 | MIC | 256 µg/mL | [125] |
| L. monocytogenes | MIC | 1.63 mM | [126] |
Carvacrol’s efficacy extends to combinations with other compounds, often resulting in synergistic or additive effects. Carvacrol/cinnamaldehyde combinations show synergistic activity against E. coli (1:0.1 ratio most effective, MIC 0.55 mg/mL) and synergism against L. innocua only when cinnamaldehyde is the major component[75]. Eugenol/carvacrol combinations exhibit synergistic/additive effects against E. coli (ratio-dependent) but antagonism against L. innocua[75], while carvacrol/thymol combinations show antagonism for E. coli but mild synergy for L. innocua at the highest carvacrol ratio[75]. Additionally, carvacrol combined with bioactive silver nanoparticles (bioAgNP) reduces carvacrol’s MIC by 67 ± 19%[62], and carvacrol/thymol combinations reduce both compounds’ MICs by 62 ± 19% and 76 ± 16%, respectively[62]. Carvacrol and cymene combinations synergistically reduce L. monocytogenes viability, with 0.75 mmol/liter of both causing a 4.7-log reduction in 10 min[114], and carvacrol/meropenem combinations show synergism against eight clinical strains, reducing colony counts by >3 log₁₀ CFU/mL[79]. However, carvacrol/cymene combinations synergistically reduce L. monocytogenes viability, with 0.75 mmol/liter of both causing a 4.7-log reduction in 10 min[114], and carvacrol/meropenem combinations show synergism against eight clinical strains, reducing colony counts by >3 log₁₀ CFU/mL[79]. However, carvacrol/1,8-cineol combinations exhibit antagonism against A. hydrophila[112], while carvacrol/cymene combinations synergistically reduce L. monocytogenes viability[114]. Carvacrol and lauric alginate combinations synergistically reduce Salmonella counts in ground turkey by 4 log cfu/g[73]. For vegetable spoilage bacteria, carvacrol + thymol, carvacrol + eugenol, and carvacrol + thymol + eugenol combinations have average MICs of 47, 43, and 42 mg/ml, respectively, with synergistic effects against multiple strains[121]. Against L. innocua, carvacrol–thymol binary mixtures have the highest number of synergistic combinations[122], and nisin/carvacrol combinations are bactericidal against L. monocytogenes[127]. Satureja hortensis essential oil (43.9% carvacrol) at 1/4 MIC synergizes with gentamicin to reduce gentamicin’s MIC to 1/16 for E. coli and shows synergistic effects (FICI < 0.38) with 1/8 gentamicin MIC for L. monocytogenes LM2[39]. O. minutiflorum essential oil (81.5% carvacrol) has indifferent effects with amoxicillin/clavulanic acid or cefimixin against S. aureus[58], while carvacrol shows antagonism with tetracycline against S. aureus IS-58 but synergism with CCCP[125]. The isonicotinamide-carvacrol (INA-CAR) cocrystal enhances carvacrol’s inhibition capability by a factor of 3 compared to chitosan-coated packaging[113].
In practical applications, carvacrol integrated into edible coatings or films effectively controls bacterial growth. A cassava starch coating with 625 μg/ml carvacrol completely inhibits E. coli, S. Typhimurium, A. hydrophila, and S. aureus in minimally processed pumpkin during storage[107], while coatings containing 0.0125 g carvacrol inhibit S. aureus growth when combined with ZnO nanoparticles[128]. In ground beef, sublethal carvacrol concentrations (1/2 and 1/4 MIC) do not induce direct or cross-tolerance in P. aeruginosa to lactic acid, salt, or high temperature[109]. Carvacrol acts rapidly: 500 μg/ml reduces E. coli O157:H7 to undetectable levels within 0.5 h[129], and against planktonic CoNS, it causes significant CFU reductions within 5 min and eliminates culturability by 15 min[110]. For biofilm-forming CoNS, carvacrol reduces cell counts by up to 4 log10 CFU/ml after 90 min[110], and against carbapenem-resistant A. baumannii, it reduces populations by 5.1 ± 0.04 log after 10 seconds[62]. Carvacrol embedded in PLGA films inhibits E. coli and S. aureus biofilm formation at 0.1% and 1.0%, respectively[118], and in carrot juice, carvacrol/cymene combinations reduce L. monocytogenes counts dose-dependently[114]. Carvacrol reduces radiation D10 values for E. coli and Salmonella Typhi in meat samples[117], and its vapor inhibits S. enterica growth and eliminates it on raw chicken surfaces[73]. Carvacrol-containing edible films inactivate E. coli, Salmonella, and L. monocytogenes on chicken breast, ham, and lettuce[73], while a 1% carvacrol chemotype essential oil sanitizer inhibits ~8 log CFU/ml of E. coli and S. enterica after 30 and 60 seconds, respectively[99]. Encapsulated carvacrol in polyethyleneimine (PEI)-coated polylactide nanoparticles maintains high activity against L. monocytogenes and S. aureus for 48–72 h[130]. Oregano essential oil (91.6% carvacrol) inhibits S. pyogenes biofilm formation and eradicates one-day-old biofilms[13], and O. minutiflorum essential oil (81.5% carvacrol) inhibits S. aureus biofilm formation at MIC, 0.5 MIC, and 0.25 MIC[58]. Satureja hortensis essential oil (43.9% carvacrol) inhibits biofilm production at 1/4 and 1/8 MIC[39], while Thymus sibthorpii (52.62% carvacrol) and Origanum vulgare (78.72% carvacrol) essential oils inhibit S. aureus biofilm formation by ~95% at half MIC[53]. ASHEO (45.15% carvacrol) suppresses biofilm formation of K. pneumoniae, A. baumannii, and E. coli by 72.8%, 64.15%, and 52.08%, respectively, at sub-MIC concentrations[89]. Carvacrol at 0.5% reduces L. monocytogenes by 4 log CFU/mL in fresh catfish fillets within 30 minutes[131], and 1.5% Zataria multiflora essential oil (66.2% carvacrol) reduces P. aeruginosa and total mesophilic aerobic bacteria on rainbow trout fillets over 12 days[131]. Carvacrol in edible films reduces Salmonella counts in leafy greens[132] and inhibits bacterial growth via direct contact and released activity in chitosan films[133]. In hake medallions, carvacrol-coated films delay bacterial growth[134], and in steak tartare, it interacts with BSA, affecting activity against L. monocytogenes[126]. Carvacrol has low phytotoxicity on olive plants[135], and the INA-CAR cocrystal maintains vapor-phase release for 14 days and achieves over 86% inhibition on treated grapes after 3–7 days[113].
Mechanisms of Carvacrol-Mediated Bacterial Growth Inhibition
Carvacrol, a monoterpenoid phenol isomer of thymol, exhibits broad-spectrum antibacterial efficacy against Gram-positive and Gram-negative bacterial strains, with activity influenced by concentration, pH, temperature, proteins, fats, salts, preservative conditions, and combination with other compounds [136]. It shows similar minimum inhibitory concentration (MIC) values to thymol for Escherichia coli and Listeria innocua, with E. coli being more susceptible [75]. Notably, carvacrol is effective against multidrug-resistant strains and is among the most inhibitory terpenes against E. coli; Gram-positive Staphylococcus aureus tends to be more sensitive to carvacrol than Gram-negative E. coli [71].
Carvacrol Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) Values Against Bacterial Strains
| Bacterial Strain | MIC Range | MBC Range | Reference(s) |
|---|---|---|---|
| Staphylococcus aureus (clinical/reference strains) | 0.39–0.78 mg·mL⁻¹ | — | [39] |
| Listeria monocytogenes | 0.78–1.56 mg·mL⁻¹ | — | [39] |
| Escherichia coli | 1.56–3.12 mg·mL⁻¹ | — | [39] |
| Acinetobacter baumannii | 0.16–0.31 mg/mL | — | [82] |
| Aeromonas hydrophila NJ-35 | 125 µg/mL | 250 µg/mL | [137] |
| Shigella sonnei | 0.1−1.0% | — | [73] |
| Shigella flexneri | 0.1−1.0% | — | [73] |
| Mycobacterium avium subsp. paratuberculosis | 72.2 μg/mL | — | [73] |
| Escherichia coli | 65 µg·mL⁻¹ | — | [97] |
| Staphylococcus aureus | 36 µg·mL⁻¹ | — | [97] |
| Clostridium perfringens | 18 µg·mL⁻¹ | — | [97] |
| Streptococcus mutans | 0.1% (93.4 μg/mL) | 0.39% (373.4 μg/mL) | [90] |
| Streptococcus sanguinis | 0.1% (93.4 μg/mL) | 0.39% (373.4 μg/mL) | [90] |
| Salmonella Enteritidis | 1.75 mM | Similar to MIC | [67] |
| Salmonella Typhimurium DT104 | 2 mM | Similar to MIC | [67] |
| Staphylococcus aureus ATCC 6538 | 78.125 µg/mL | — | [138] |
| Escherichia coli ATCC 10536 | 156.25 µg/mL | — | [138] |
| Pseudomonas aeruginosa ATCC 15442 | 625 µg/mL | — | [138] |
| Enterococcus hirae ATCC 10541 | 312.5 µg/mL | — | [138] |
| Escherichia coli (ATCC 25922) | 1.0–2.0 mmol·L⁻¹ | — | [139] |
| Staphylococcus aureus (ATCC 25923) | 0.5–1.0 mmol·L⁻¹ | — | [139] |
| Pseudomonas savastanoi pv. savastanoi | 1.25 mg/mL | — | [135] |
| Pseudomonas aeruginosa (free carvacrol) | 5 mg/mL | — | [64] |
| Pseudomonas aeruginosa (encapsulated carvacrol) | 1.25 mg/mL | — | [64] |
| Enterococcus faecalis (free/encapsulated carvacrol) | 0.625 mg/mL | — | [64] |
Carvacrol’s efficacy is enhanced under acidic conditions: at pH 4.0, 50 μL·L⁻¹ carvacrol inactivates >5 log₁₀ cycles of L. monocytogenes within 5 h, compared to 1 log₁₀ cycle for E. coli [115]. At 8 ˚C (upper refrigeration temperature), increasing carvacrol concentration reduces the maximum growth rate (μmax) of L. innocua; 0.125 μL/mL carvacrol lowers μmax to 0.006 (log₁₀cfu/mL)/h—3 times smaller than the value without carvacrol [140].
Binary combinations of carvacrol with other compounds often yield synergistic effects. Carvacrol/cinnamaldehyde combinations show synergism against E. coli across most ratios (1:0.1 ratio has lowest MIC of 0.55 mg/mL) [75] but are synergistic against L. innocua only when cinnamaldehyde is the major component (0.5:4 ratio, MIC 0.45 mg/mL) [75]. Associations with carvacrol are also synergistic against Enterobacter aerogenes and E. coli [51]. In contrast, carvacrol/thymol combinations are antagonistic against E. coli but mildly synergistic against L. innocua at the highest carvacrol ratio [75], while eugenol/carvacrol combinations are antagonistic against L. innocua but synergistic or additive against E. coli depending on the ratio [75]. Carvacrol and lauric alginate act synergistically to reduce Salmonella counts in ground turkey by 4 log cfu/g [73]. Microencapsulation improves carvacrol’s solubility and bioavailability: encapsulated carvacrol (E-CARV) has a lower bactericidal concentration (BIC) than carvacrol solution against Salmonella enterica and L. monocytogenes (p < 0.05) [98]. Carvacrol-loaded PLA nanofiber webs show dose-dependent activity, with 10% carvacrol (C10) inhibiting over 92% of E. coli and S. epidermidis growth within 24 h [101]. Combinations with mild heat treatment or weak organic acids enhance carvacrol’s effects [136]. The carvacrol/nerol (C + N*) combination shows synergistic activity against S. aureus, P. aeruginosa, E. coli, and E. hirae (fractional inhibitory concentration indices [FICI] 0.5–0.25) [138]; at 80X and 100X ratios, it achieves >5 log reduction in viable counts of both Gram-positive and Gram-negative bacteria after 1-minute contact time [138]. Conversely, carvacrol/tetracycline combinations are antagonistic against S. aureus IS-58, increasing tetracycline’s MIC from 128 to 203 µg/mL [125].
The primary mechanism of carvacrol-mediated inhibition involves disrupting cell membrane integrity. As a hydrophobic compound, carvacrol disturbs the outer membrane of Gram-negative bacteria, releasing lipopolysaccharides and increasing cytoplasmic membrane permeability to ATP [75][51]. It causes leakage of intracellular potassium (K⁺) ions—1 mM carvacrol reduces bacterial cell K⁺ content within 5 min, indicating membrane damage [72]. Adding 0.1% carvacrol results in 90% ± 0.7 fluorescent cells of Ps. aeruginosa and Staph. aureus, indicating impaired membranes and accessible intracellular nucleic acids [78]. Exposure of Bacillus cereus to carvacrol depletes intracellular ATP pools, alters membrane potential, and increases cytoplasmic membrane permeability for protons and potassium ions [73]. Carvacrol modifies lipid monolayer structures by integrating into the monolayer, forming antimicrobial−lipid complexes, reducing lipid packing, increasing fluidity, and altering the total dipole moment [73]. It causes concentration-dependent carboxyfluorescein (CF) leakage from large unilamellar vesicles (LUVs) and markedly decreases dimyristoylphosphatidylcholine (DMPC) melting temperature (Tm), with stronger effects at higher molar fractions [71]. Thymol and carvacrol act on the outer membrane of Gram-negative bacteria, provoking lipopolysaccharide release, increasing cytoplasmic membrane permeability, and depolarizing the membrane [97]. At pH 4.0, carvacrol alters β-sheet proteins (1624 cm⁻¹) and COO⁻ groups (1395 cm⁻¹); at pH 7.0, it affects phosphodiester bonds in cell membranes (1083 and 1215 cm⁻¹) [115].
Carvacrol also causes concentration-dependent release of intracellular components: 0.02–0.1% (v/v) carvacrol increases 260 nm absorbing material (DNA/RNA) release linearly in E. coli and B. subtilis over 24 h [105]. Treatment of E. coli and S. aureus with carvacrol above MIC triggers significant genetic material release (260 nm absorbance) and increased membrane permeability (o-nitrophenyl-β-D-galactopyranoside [ONPG] hydrolysis at 420 nm) [139]. Against P. savastanoi pv. savastanoi, carvacrol provokes stronger protein and DNA leakage than oregano essential oil [135]. Key structural features—free phenolic hydroxyl group and hydrophobicity—drive bioactivity; O-methyl derivatives lack activity against Gram-negative E. coli and have limited activity against Gram-positive S. aureus, as they fail to cause ion leakage or genetic material release [139][136].
Carvacrol depletes intracellular ATP pools by reducing synthesis and increasing hydrolysis, lowering internal pH from 7.1 to 5.8 at 1 mM [72], and inhibiting ATP synthesis by disrupting the respiratory chain [87]. It reduces intracellular ATPase activity and increases extracellular ATPase activity in S. aureus [141]. For Salmonella, sub-lethal concentrations (0.8 mM) cause significant extracellular ATP leakage in log-phase cells [67]. Additionally, carvacrol induces rRNA degradation in A. baumannii [82] and upregulates heat shock genes (groES, groEL, dnaK, clpB) and oxidative stress genes (katE) in response to cell damage [82]. It binds to critical enzymes involved in cell wall, protein, and nucleic acid biosynthesis/repair with binding free energies of −5.2 to −8.1 kcal/mol [89]. At sub-MIC concentrations, it inhibits biofilm formation and extracellular polymeric substance (EPS) production in A. hydrophila [137] and reduces virulence gene expression (e.g., flaB, aha, ompA) [137]. Continuous carvacrol exposure is as effective as commercial sanitizers in inhibiting biofilm formation by S. aureus and S. enterica [73], and it inhibits oral pathogens (Fusobacterium nucleatum, Porphyromonas gingivalis, Streptococcus mutans) and their preformed biofilms on titanium discs [73]. Carvacrol has a significant anti-biofilm effect on S. aureus at 0.078 mg/mL (p < 0.05), with increasing effect at higher concentrations [141]. In packaging, carvacrol vapor (1.08 × 10⁻⁷ g·mL⁻¹) from films inhibits growth of B. subtilis, E. coli, L. innocua, and S. Enteritidis by permeabilizing cell membranes [95]; it also inhibits S. enterica growth and eliminates the pathogen on raw chicken surfaces [73]. Growth in carvacrol increases relative amounts of iso-C13:0, C14:0, and iso-C15:0 fatty acids and reduces cis-C16:1 and C18:0 fatty acids in B. cereus [142]. Cells pre-exposed to carvacrol are less sensitive to subsequent exposure than non-adapted cells, with concentration-dependent decreased sensitivity [142]. The C + N* combination impairs the EPS matrix of mature mono-species (S. aureus) and mixed-species (S. aureus + P. aeruginosa) biofilms, reducing carbohydrate, protein, and lipid contents [138][136]. Novel carvacrol codrugs show improved antimicrobial/antibiofilm activities and reduced toxicity [136].
Synergistic and Combined Antibacterial Effects of Carvacrol with Other Compounds
Carvacrol exhibits broad-spectrum antibacterial and antifungal efficacy against diverse microbial strains, with dose-dependent and strain-specific effects that vary by application context (e.g., temperature, food models) [143][144][145][114][79][119][121][122][58][146][147][125][140]. Its activity spans Gram-negative bacteria (e.g., E. coli, A. baumannii, S. enteritidis), Gram-positive bacteria (e.g., L. innocua, B. cereus, E. faecalis, S. aureus), and fungal isolates (e.g., C. albicans) [143][145][146]. Additionally, wild oregano essential oil (81.5% carvacrol) demonstrates antibacterial activity against strains including S. dysgalactiae and S. aureus [58].
Carvacrol’s Antimicrobial Activity Against Specific Microbial Strains and Contexts
| Microorganism/Context | Key Findings | Citation(s) |
|---|---|---|
| Diverse bacterial strains | MIC range: 32–128 µg/mL; active against Gram-negative and Gram-positive bacteria | [143][145][79] |
| B. cereus | 0.19 mg/g: ~1 log unit reduction in final population; 0.38 mg/g: full growth suppression; 0.53 mg/g: counts below detection within 7 days | [144] |
| Salmonella serovars (S. enteritidis, S. senftenberg) | 0.77 mM: doubled stationary phase time for S. enteritidis (7→15 h); ~2 h increase for S. senftenberg; S. enteritidis showed greater growth rate reduction | [145] |
| L. monocytogenes | 2.0 mmol/L: >3 log cycle reduction in <15 min; lower concentrations showed biphasic reductions | [114] |
| A. hydrophila, E. coli | 100 ppm: bactericidal against A. hydrophila; 200 ppm: bactericidal against E. coli | [112] |
| Oral pathogens (E. coli) | E. coli more sensitive to carvacrol than thymol (inhibition zones in diffusion tests) | [119] |
| 15 vegetable spoilage bacteria | Average MIC: 167 mg/mL; average MBC: 555 mg/mL (lower than thymol’s average MIC of 648 mg/mL) | [121] |
| L. innocua (liquid media) | MBC: 150 mg kg⁻¹ | [122] |
| Wild oregano EO (81.5% carvacrol) | MIC range: 0.03–1.38 mg/mL (S. dysgalactiae: 0.05 mg/mL; S. aureus: 1.38 mg/mL) | [58] |
| C. albicans and co-isolated bacteria | C. albicans MIC: 0.25–1 mg/mL; co-isolated bacteria MIC: 1 mg/mL | [146] |
| S. aureus IS-58 strain | MIC: 256 µg/mL | [125] |
| Lactobacillus curvatus (meat model, formulation AR) | 10.9% reduction in maximum growth rate | [147] |
| E. coli K12, L. innocua | MIC values vary by temperature (37, 30, 15, 8 ˚C); more effective against E. coli K12 than L. innocua; reduced E. coli K12 μmax and increased lag phase across temperatures | [140] |
The mechanisms underlying carvacrol’s activity center on membrane disruption: as a hydrophobic compound, it disturbs the outer membrane of Gram-negative bacteria, releasing lipopolysaccharides and increasing cytoplasmic membrane permeability to ATP [75][51]. This is supported by observations of impaired cell membranes (via fluorescent nucleic acid staining), increased potassium/phosphate leakage, and dissipation of internal pH gradients in Ps. aeruginosa and Staph. aureus [78]. In Gram-negative bacteria, carvacrol disintegrates the polysaccharidic capsule, increases membrane fluidity, disrupts the proton motive force, and inhibits ATP/DNA synthesis [148]. Collectively, its effects include destabilizing cell membranes, depleting intracellular ATP pools, and disrupting the proton-motive force [140].
Carvacrol also shows context-dependent synergistic or antagonistic interactions with various compounds. Synergism is common with terpenoids, antibiotics, and other agents, though some combinations (e.g., carvacrol/thymol against E. coli) exhibit antagonism [75][41][112][114][79][149][121][122][150][146][151][152][138][153][147][154][155].
Synergistic and Antagonistic Interactions of Carvacrol with Other Compounds
| Combination | Microorganism(s) | Key Findings | Citation(s) |
|---|---|---|---|
| Carvacrol/cinnamaldehyde | E. coli, L. innocua | Synergistic against E. coli (1:0.1 ratio most effective, MIC 0.55 mg/mL); synergistic against L. innocua when cinnamaldehyde is major (0.5:4 ratio, MIC 0.45 mg/mL) | [75] |
| Eugenol/carvacrol | E. coli, L. innocua | Synergistic/additive against E. coli; antagonistic against L. innocua | [75] |
| Carvacrol/cymene | L. monocytogenes, B. cereus | L. monocytogenes: 0.75 mmol/L each → 4.7 log reduction in 10 min (vs. 0.6 log with carvacrol alone over 20 min); B. cereus: 0.5 mM + 0.25 mM → 50% count reduction in 48 min | [144][114] |
| Carvacrol/meropenem | 8 clinical strains | Synergistic (FICI 0.5); reduced meropenem MICs by fourfold | [79] |
| Carvacrol/thymol or gallic acid | E. faecalis | Synergistic/additive (FICI 0.5–0.75) | [149] |
| Carvacrol/borneol (with thymol) | Bacteria | Synergistic via action with thymol | [41] |
| Carvacrol/fatty acids (formulation SYN) | Brochothrix thermosphacta, Lactobacillus curvatus | Stronger inhibition than fatty acids alone (P < 0.05); almost bactericidal against B. thermosphacta; 63.3% reduction in L. curvatus specific growth rate | [147] |
| Carvacrol/nisin | B. subtilis, L. innocua | Synergistic | [154] |
| Carvacrol/citral | L. monocytogenes, L. innocua | Potentiated antibiotic activity (reduced bacitracin/colistin MICs); prolonged lag phases and caused sublethal damage at higher concentrations | [151][155] |
| Carvacrol/ZnO (composite sponges) | E. coli, S. aureus | Synergistic antibacterial activity | [150] |
| Carvacrol (S. thymbra EO)/honey | E. coli, S. faecalis | Partial/total synergism (FICI 0.156–0.312) | [152] |
| Carvacrol/nerol | S. aureus, P. aeruginosa, E. coli, E. hirae | Synergistic (FICI 0.25–0.5) | [138] |
| Carvacrol/cuminaldehyde | C. albicans (12 strains) | Synergistic (FICI 0.36–0.5); reduced SMIC50 ~8-fold for cuminaldehyde, 4-fold for carvacrol | [146] |
| Carvacrol/XTZ + PMBN (triple) | V. cholerae, E. coli | Synergistic; complete killing of E. coli within 2 h | [153] |
| Carvacrol/thymol | E. coli | Antagonistic at all ratios | [75] |
| Carvacrol/1,8-cineol | A. hydrophila | Antagonistic | [112] |
| Carvacrol/tetracycline | S. aureus IS-58 | Antagonistic; increased tetracycline MIC from 128 to 203 µg/mL | [125] |
| Carvacrol/CCCP | S. aureus IS-58 | Synergistic | [125] |
| Carvacrol/chlorpromazine | S. aureus IS-58 | No difference from control | [125] |
| Carvacrol/thymol | L. innocua | Highest number of synergistic bactericidal combinations | [122] |
| Carvacrol/eugenol | 10 of 15 vegetable spoilage bacteria | Synergistic | [121] |
| Carvacrol/amoxicillin-clavulanic acid/cefimixin | S. aureus | Indifferent effects | [58] |
Notably, carvacrol combinations with fatty acids (formulation SYN) showed stronger inhibition of Lactobacillus curvatus (63.3% reduction in specific growth rate) and almost bactericidal effects against Brochothrix thermosphacta in a meat model [147]. Triple combinations (e.g., XTZ + PMBN + carvacrol) achieved complete killing of E. coli within 2 hours [153], while carvacrol combined with zinc oxide or honey enhanced activity against E. coli and S. aureus [150][152]. Antagonism, however, limits efficacy in some cases, such as carvacrol/tetracycline against S. aureus IS-58 [125].
Formulated Carvacrol Applications for Bacterial Growth Inhibition
Carvacrol exhibits broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacterial strains, with distinct modes of action: bactericidal effects on Gram-negative and bacteriostatic effects on Gram-positive microorganisms [113]. Its efficacy varies by bacterial strain, formulation, and application method, as summarized in the tables below. Notably, carvacrol is more effective against Gram-positive bacteria due to differences in cell wall composition [130], a trend observed in gelatin films where it was most effective against Bacillus subtilis and S. aureus, followed by E. coli and P. aeruginosa [156].
Carvacrol Minimum Inhibitory Concentrations (MIC) Against Bacterial Strains
| Bacterial Strain | MIC Value | Method/Context | Citation |
|---|---|---|---|
| Escherichia coli (ATCC 25922) | 312 μg/ml | Broth microdilution | [107] |
| Salmonella enterica ser. Typhimurium (ATCC 14028) | 312 μg/ml | Broth microdilution | [107] |
| Aeromonas hydrophila (ATCC 7966) | 312 μg/ml | Broth microdilution | [107] |
| Staphylococcus aureus (ATCC 25923) | 312 μg/ml | Broth microdilution | [107] |
| Pseudomonas aeruginosa (ATCC 9027) | 0.6 mL/mL | Not specified | [109] |
| Shigella sonnei | 0.1−1.0% | Not specified | [73] |
| Shigella flexneri | 0.1−1.0% | Not specified | [73] |
| Mycobacterium avium subsp. paratuberculosis | 72.2 μg/mL | Not specified | [73] |
| Enterococcus faecalis (free/encapsulated) | 0.625 mg/mL | Not specified | [64] |
| Staphylococcus aureus | 1.0 mM | Growth inhibition threshold | [118] |
| Escherichia coli | 1.5 mM | Growth inhibition threshold | [118] |
| Pseudomonas aeruginosa | 4 mM (highest tested) | Growth inhibition threshold | [118] |
| Escherichia coli | 65 µg·mL⁻¹ | Not specified | [97] |
| Staphylococcus aureus | 36 µg·mL⁻¹ | Not specified | [97] |
| Clostridium perfringens | 18 µg·mL⁻¹ | Not specified | [97] |
Formulated Carvacrol Applications and Efficacy in Food Systems
| Formulation/Application | Target Microorganisms/Effect | Citation |
|---|---|---|
| Edible cassava starch coating (625 μg/ml carvacrol) | Complete inhibition of E. coli, S. Typhimurium, A. hydrophila, S. aureus in minimally processed pumpkin (7 days refrigerated) | [107] |
| Edible cassava starch coating (312 μg/ml carvacrol) | Up to 8 log CFU/g reduction of target bacteria in minimally processed pumpkin (7 days refrigerated) | [107] |
| Microbial biopolymer (MB) foams (20% carvacrol) | Inhibited Listeria monocytogenes, Pseudomonas poae, Salmonella strains, Enterobacter amnigenus in vitro; reduced/eliminated TMM, L. monocytogenes, P. poae in refrigerated melon/pumpkin (7 days) | [157] |
| Carvacrol-loaded PLA nanofiber webs (10% carvacrol, C10) | >92% inhibition of E. coli (complete by 2 h) and S. epidermidis (complete by 4 h) within 24 h | [101] |
| Encapsulated carvacrol vs. free carvacrol | Lower MIC against P. aeruginosa (1.25 mg/mL vs. 5 mg/mL); reduced P. aeruginosa biofilm by >5 log CFU/mL and eliminated E. faecalis biofilm by 5.5 log CFU/mL (15 min at MIC) | [64] |
| PEI-coated PLA nanoparticles (CAR-(PEI)NPs) | Enhanced long-term efficacy: MIC against L. monocytogenes and S. aureus (128–256 μg/mL at 48 h vs. >1024 μg/mL for free carvacrol); activity maintained at 72 h | [130] |
| Carvacrol-loaded chia/flaxseed nanoparticles | Bactericidal concentrations (BIC) of 0.42 mg/mL (chia) and 0.83 mg/mL (flaxseed) against Salmonella enterica cocktails | [98] |
| Apple films (3% carvacrol) | Reduced Salmonella to <1 log CFU/g (day 0) and maintained 1.8–4.6 log CFU/g reductions in leafy greens (7 days) | [132] |
| Chitosan films (20% carvacrol) | Inhibited Pseudomonas fragi, Shewanella putrefaciens, A. hydrophila via direct contact and release | [133] |
| WPI coatings (2.16% carvacrol) | Delayed growth of mesophilic, psychrotrophic, Pseudomonas, Enterobacteriaceae, and H₂S-producing bacteria in hake medallions (12 days storage) | [134] |
| Sanitizing solutions (1% carvacrol-rich EO6) | Inhibited ~8 log CFU/ml of E. coli and S. enterica within 30–60 seconds | [99] |
Carvacrol’s antibacterial mechanism centers on membrane disruption: its hydrophobicity drives accumulation in cell membranes, causing permeabilization, potassium ion leakage, and release of cytoplasmic contents (e.g., GFP in P. aeruginosa) [95][64]. It also reduces lipid packing effectiveness, increases membrane fluidity, and alters lipid monolayer dipole moments [73]. Encapsulated carvacrol induces greater membrane damage in P. aeruginosa than free carvacrol, as shown by 6.5-fold vs. 2.6-fold higher extracellular GFP fluorescence after 40 min [64]. Additional mechanisms include intracellular ATP pool depletion, membrane potential disruption, and ATP synthesis inhibition [96][73]. Sublethal concentrations (1/2 and 1/4 MIC) do not induce direct or cross-tolerance in P. aeruginosa to lactic acid, salt, or high temperature in ground beef [109]. For L. monocytogenes, carvacrol acts via multi-target effects (membrane disruption, lysis, respiratory inhibition), with continuous energetic pool depletion from PEI-coated nanoparticles contributing to long-term efficacy [130]. For Gram-negative bacteria, it provokes lipopolysaccharide release, increases cytoplasmic membrane permeability, and depolarizes membranes [97]; its free phenolic hydroxyl group and hydrophobicity are key structural determinants of bioactivity [136].
In food matrices, carvacrol vapor from high mass transfer coefficient (Kmass) films inhibits B. subtilis, E. coli, L. innocua, and S. Enteritidis, with minimal vapor inhibitory concentrations of 4.62 × 10⁻⁸ to 1.08 × 10⁻⁷ g mL⁻¹ [95]. It reduces radiation D10 values for E. coli (0.126 → 0.057 kGy) and Salmonella Typhi (0.519 → 0.235 kGy) in meat, with modified atmosphere packaging (MAP) enhancing sensitivity [117]. Carvacrol vapor eliminates S. enterica on raw chicken surfaces [73], while edible films inactivate E. coli, Salmonella, and L. monocytogenes on chicken breast, ham, and lettuce [73]. Combinations with lauric alginate synergistically reduce Salmonella in ground turkey by 4 log cfu/g [73]. Spraying 1.5% Zataria multiflora EO (66.2% carvacrol) with potassium sorbate controls L. monocytogenes and spoilage bacteria in rainbow trout fillets [131]. Its efficacy is influenced by pH, proteins, fats, salts, temperature, and preservative conditions [136], with combinations with mild heat or weak organic acids enhancing effects [136].
Formulated applications and combinations further enhance carvacrol’s efficacy. Synergistic effects against 10 of 15 vegetable spoilage bacteria are observed with carvacrol + thymol or carvacrol + eugenol [121], and carvacrol + nisin is bactericidal against L. monocytogenes [127]. A novel isonicotinamide-carvacrol (INA-CAR) cocrystal (1:1 M ratio, stabilized by hydrogen bonds including hydroxyl⋅⋅⋅pyridine interactions (N⋅⋅⋅O = 2.757(2) Å)) has been developed via 10-minute mortar grinding of 1 mmol isonicotinamide and 1 mmol carvacrol [113]. This cocrystal enhances antimicrobial inhibition in packaging prototypes by a factor of 3 relative to chitosan-coated packaging [113], with constant vapor-phase active component release for 14 days [113] and >86% microbial growth inhibition on grapes after 3 and 7 days [113]. Microencapsulation also improves solubility and bioavailability, with antimicrobial effects detectable as early as 2 h post-incubation [76] and controlled evaporation critical for food preservation [130].
Carvacrol-Based Formulations and Delivery Systems for Enhanced Antibacterial Activity
Carvacrol's Mechanisms of Antibacterial Action Against Planktonic Cells, Biofilms, and Membrane Permeability
Carvacrol, a monoterpenoid phenol and GRAS-listed compound, exhibits potent antibacterial activity against diverse pathogens including Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, and Enterococcus faecalis[87][64][96]. Its primary mechanism targets bacterial cell membranes: the hydroxyl group increases cytoplasmic membrane permeability, disrupts membrane pH gradients, inhibits ATP synthesis, and causes leakage of intracellular contents (e.g., potassium ions, GFP) leading to cell death[38][95][87][64][96]. Gram-positive bacteria (e.g., S. aureus) are generally more sensitive than Gram-negative species (e.g., P. aeruginosa), as the latter’s lipopolysaccharide outer membrane restricts diffusion of hydrophobic carvacrol[38][87]. Synergistic effects with p-cymene (which swells cell membranes to facilitate carvacrol entry) and thymol further enhance its efficacy[38][76].
Formulations improve carvacrol’s solubility, bioavailability, and stability, thereby boosting antibacterial performance. Key findings from carvacrol formulation studies are summarized below:
Antibacterial Efficacy of Carvacrol Formulations vs. Free Carvacrol
| Formulation Type | Key Antibacterial Activity | Target Microorganism(s) | Citations |
|---|---|---|---|
| 2% carvacrol-rich essential oil films | Greatest inhibition zones against tested microorganisms | Not specified (tested pathogens) | [38] |
| C10 concentration PLA nanofiber webs | >92% inhibition of growth within 24h; complete E. coli suppression within 2h | E. coli, S. epidermidis | [101] |
| Spray-dried microencapsulated carvacrol (E-CARV) | 4-fold lower MIC vs. free carvacrol (F-CARV); greater potassium ion/GFP leakage; >5 log CFU mL⁻¹ biofilm biomass reduction in 15min at MIC | P. aeruginosa (planktonic and biofilms) | [64] |
| Carvacrol-loaded chitosan nanoparticles (Th-CNPs) | 4–7-fold lower MIC vs. pure thyme essential oil | L. monocytogenes, S. aureus, E. coli | [70] |
| OEO-loaded solid lipid nanoparticles (SMV) | Maintained antibacterial activity for 72h; prevented regrowth (unlike free essential oil) | E. coli, S. epidermidis | [66] |
| Carvacrol-rich SMEO films (1.08 × 10⁻⁷ g mL⁻¹ vapour concentration) | Complete inhibition via vapour-phase membrane permeabilization and cell lysis | Listeria innouca | [95] |
| Carvacrol-rich SMEO (53.58% carvacrol) | Reduced pathogen growth in fresh pork sausage | Foodborne pathogens (unspecified) | [96] |
Carvacrol also targets bacterial biofilms, with formulations enhancing this activity. For example, E-CARV achieved rapid biofilm reduction compared to F-CARV[64]. SEM analysis of treated biofilms revealed cell shrinkage, deflation, and wall damage, confirming membrane destruction[64][66]. In food applications, carvacrol-rich essential oils and loaded films inhibit pathogens via direct or vapour-phase activity[95][96]. Collectively, these formulations highlight carvacrol’s potential for controlled release and sustained antibacterial activity in food, medical, and pharmaceutical contexts[87][64][70][66].
Efficacy of Free and Combined Carvacrol Against Bacterial Pathogens and Spoilage Organisms
Carvacrol, a monoterpenoid phenol isomer of thymol, is a major component of aromatic plants like Thymus capitatus (up to 74.4%) and T. vulgaris (up to 60%) and is recognized as Generally Recognized as Safe (GRAS) for food use [87]. Its broad-spectrum antibacterial activity targets pathogens and spoilage organisms including S. aureus, E. coli, P. syringae, P. damselae, A. hydrophila, S. iniae, L. monocytogenes, Salmonella Typhimurium, and various vegetable spoilage bacteria [158][128][87][121]. Mechanistically, it disrupts bacterial cell membranes, causing potassium ion leakage, increased permeability, and cytoplasmic content leakage (e.g., GFP in P. aeruginosa), which leads to cell death [64][96]; it also reduces ATP synthesis and the cytoplasmic membrane pH gradient [96].
Carvacrol Formulations: Antibacterial Efficacy vs. Free Carvacrol
| Formulation Type | Source/Composition | Target Organism(s) | Key Outcome(s) | Citations |
|---|---|---|---|---|
| Nano-emulsion | O. vulgare (carvacrol-rich) | P. damselae, A. hydrophila, S. iniae | MIC/MBC = 3.12 µg/ml; outperformed tetracycline | [158] |
| Nano-emulsion | Satureja essential oil (SEO3, high carvacrol) | S. aureus, E. coli, S. marcescens | Reduced MIC values compared to free oil | [159] |
| Microencapsulated (E-CARV) | Carvacrol | P. aeruginosa | MIC = 1.25 mg/mL (vs. 5 mg/mL free carvacrol); >99% biofilm biomass reduction | [64] |
| Microencapsulated (MO1/MO2/MO3) | Carvacrol | E. coli | 4-fold MBC reduction (MO1); 2-fold MBC reduction (MO2, MO3) | [160] |
Carvacrol Combinations: Synergistic Antibacterial Effects
| Combination Partner(s) | Target Organism(s) | Key Outcome(s) | Citations |
|---|---|---|---|
| Thymol | L. innocua | Highest number of synergistic bactericidal combinations | [122] |
| Thymol | 15 vegetable spoilage bacteria | Average MIC = 47 mg/ml; synergistic effects against 10 strains | [121] |
| Eugenol | 15 vegetable spoilage bacteria | Average MIC = 43 mg/ml; synergistic effects against 10 strains | [121] |
| Nisin | L. monocytogenes | Bactericidal activity | [127] |
| Citral | Listeria species | Reduced bacitracin MIC from 32.0 µg/ml to 1.0 µg/ml | [155] |
| Potassium sorbate | Bacteria | Synergistic effects (FIC Index 0.405–0.833) | [161] |
Carvacrol’s efficacy is modulated by environmental conditions: its MIC decreases under less favorable conditions (low pH and/or low aw) [161]. It also exhibits a prolonged vapor phase effect compared to thymol, with inhibition zones remaining visible at 96 h while thymol’s zones disappeared [119]. In food applications, carvacrol controls pathogens in rice, tomatoes, grapes, and milk, and its supplementation in broilers improves meat quality by inhibiting lipid oxidation [87]. Notably, its activity against spoilage bacteria is stronger than organic acids, with average MICs of 167 mg/ml against 15 vegetable spoilage bacteria, compared to 1385 mg/ml for acetic acid [121].
Carvacrol-Based Encapsulation and Nanoformulation Strategies for Enhanced Antibacterial Activity
Encapsulation and nanoformulation strategies enhance carvacrol’s antibacterial efficacy by addressing key limitations (volatility, poor water solubility) and enabling targeted delivery, while also boosting anti-biofilm activity. These strategies modify carvacrol’s stability, release kinetics, and interaction with bacterial cells, with carrier materials dictating encapsulation efficiency, release profiles, and performance against Gram-positive and Gram-negative pathogens.
Carvacrol Formulation Efficacy and Key Parameters Across Carriers
| Formulation Type | Key Characteristics & Outcomes | Target Pathogen(s) | Citation(s) |
|---|---|---|---|
| Spray-dried microcapsules (sodium caseinate + maltodextrin DE19) | Spherical, hollow structures; preserved activity post-reconstitution; >99% P. aeruginosa biofilm reduction at MIC (15 min) | S. aureus, Gram-negative bacteria, P. aeruginosa, E. faecalis | [64] |
| Whey-containing Pickering emulsions (whey-NEO) | Outperformed free EO (whey-EO) in coatings (reduced evaporation, better protection) | Not specified (antibacterial coatings) | [162] |
| 0.5% carvacrol nanoemulsion hydrogel | Bactericidal; conventional cream at same concentration inactive (slower release) | S. aureus, Gram-negative bacteria | [163] |
| TEO-chitosan nanoparticles (TEO-CSNPs) | Encapsulation efficiency: 80.5±1%; 100% carvacrol release in 390 min; max inhibition halo (IH) 4.3 cm (S. aureus); MIV 2.5 μL (6 strains) | S. aureus | [164] |
| TEO-chitosan nanocapsules (TEO-CSNCs) | Encapsulation efficiency: 81.4±1%; slower release than TEO-CSNPs; higher MIVs (5–10 μL) for most strains | Not specified (compared to TEO-CSNPs) | [164] |
| Th-CNPs (chitosan nanoparticles) | MIC 0.03 mg/mL (L. monocytogenes; 33-fold lower than pure thyme EO) | L. monocytogenes | [70] |
| β-cyclodextrin (BCD) inclusion complexes | 65–72.7% lower MIC than free carvacrol (improved solubility) | E. coli K12, S. Typhimurium | [165] |
| CAR-(PEI)NPs (PLA + polyethyleneimine) | MIC 128–256 μg/mL (L. monocytogenes, S. aureus; free carvacrol >1024 μg/mL); stable over 72 h | L. monocytogenes, S. aureus | [130] |
| Organically modified montmorillonite/bentonite nanocarriers (LDPE films) | Complete E. coli inhibition at specific carvacrol-thymol ratios | E. coli | [166] |
| Biopolymeric suspensions (0.4% EO, 1% zein + MD/GA) | 0.4% wt. EO; GA formulations superior to MD (enhanced membrane permeability) | E. coli, S. typhimurium, L. monocytogenes | [167] |
| EO-loaded microcapsules (MO1, MO2, MO3) | MO1 reduced E. coli MBC 4-fold; MO1/MO2 reduced S. aureus MBC 2-fold (vs. pure EOs) | E. coli, S. aureus | [160] |
| OEO-loaded solid lipid nanoparticles (SMV) | MIC 0.64 mg/mL (E. coli, S. epidermidis; free OEO 1.28 mg/mL); sustained activity over 72 h | E. coli, S. epidermidis | [66] |
| Chia/flaxseed nanoparticles | Lower BIC against S. enterica (0.42 mg/mL) and L. monocytogenes vs. free carvacrol (1.77 mg/mL) | S. enterica, L. monocytogenes | [98] |
| Microencapsulated additive (AROTEC-G®) | Reduced V. anguillarum/P. anguilliseptica growth in fish skin mucus (50.2±1.6% P. anguilliseptica reduction at 14 h) | V. anguillarum, P. anguilliseptica | [168] |
Anti-biofilm effects are amplified by encapsulation: spray-dried microencapsulated carvacrol (E-CARV) reduced P. aeruginosa biofilm biomass by >99% at MIC (15 min), while free carvacrol (F-CARV) only achieved a 4.8 log CFU/mL reduction [64]. Mechanistically, E-CARV induced 4.6–6.5-fold higher protein leakage (extracellular GFP fluorescence) in P. aeruginosa than F-CARV within 40 min [64]. Nanoencapsulated carvacrol disrupts bacterial cytoplasmic membranes—causing potassium/proton leakage and membrane depolarization—with sustained release from carriers amplifying these effects [70][64]. OEO-loaded SMV further exemplifies this: it adhered to S. epidermidis surfaces, disintegrated membranes, and caused E. coli cell wall damage, aligning with carvacrol’s outer membrane dissolution mechanism [66].
Release kinetics depend on carrier concentration: lower encapsulant levels (e.g., 2% SP vs. 5% SP) accelerate release, with K values of 3.27 × 10⁻⁴ and 1.51 × 10⁻⁴, respectively [169]. Carvacrol’s liquid state (vs. crystalline thymol) contributes to higher encapsulation efficiency and faster release rates than thymol, though total released amounts are lower [169]. Collectively, these strategies enhance carvacrol’s potency against a broad range of pathogens in both laboratory and food-relevant applications.
Carvacrol-Incorporated Edible and Plastic Films for Food Preservation Applications
Carvacrol, a monoterpenoid phenol and GRAS-listed compound, is a key antimicrobial agent for food preservation, with World Health Organization approval for use in various food products and residue limits up to 50 mg/kg [87]. Its antimicrobial activity stems from structural features (hydroxyl group, delocalized electrons) that disrupt bacterial cell membranes, alter respiration, reduce ATP synthesis, and cause membrane permeabilization [87][100]. For example, carvacrol accumulation in cell membranes modifies hydrogen bonding to induce cell death [95], and electron micrographs of oregano oil-treated (carvacrol-rich) cells show disrupted membranes and morphological damage [61]. Gram-positive bacteria (e.g., S. aureus) are generally more sensitive to carvacrol than Gram-negative bacteria (e.g., E. coli, P. aeruginosa) due to the latter’s outer membrane lipopolysaccharides restricting hydrophobic compound diffusion [38][100]. However, carvacrol can disintegrate Gram-negative outer membranes to increase cytoplasmic permeability [38], and synergies with components like p-cymene (which swells membranes to facilitate carvacrol entry) enhance activity [38].
Carvacrol-Incorporated Films: Matrix, Loading, Activity, and Key Observations
| Film Matrix | Carvacrol Loading/Formulation | Target Microorganisms/Activity Outcomes | Key Observations | Citations |
|---|---|---|---|---|
| Sodium/calcium caseinate (SC/CC) | Not specified (via agar diffusion) | S. aureus (larger inhibition zones), E. coli | SC films release carvacrol more effectively than CC films (calcium cross-linking retains carvacrol) | [100] |
| PLA_PHB + oleic acid (OLA) | 10 wt% | S. aureus, E. coli (bactericidal within 3 hours, maintained 24 hours) | — | [42] |
| Polyvinylidene fluoride (PVDF) | 1% (w/w) | High antibacterial efficiency initially; lost inhibition after 3 months (evaporation) | — | [170] |
| Polypropylene (PP) | Not specified (molten extrusion) | E. coli, Alternaria alternata (inhibition) | — | [87] |
| Chitosan | High mass transfer coefficient (Kmass) | B. subtilis, E. coli, L. innocua, S. Enteritidis (complete inhibition via vapor release) | Carvacrol vapor solubilizes in cell membranes | [95] |
| Ethylene vinyl acetate (EVA) | CAR alone; ALD+CAR (25+75%) | Anti-biofilm (60–80% biomass reduction vs. control at 22°C/37°C) | — | [171] |
| Tomato/apple-based edible | 0.5–0.75% (w/w in film-forming solution) | Volatile loss: 60.1 ± 6.5% carvacrol (adjusted for water removal/casting) | — | [172] |
| Cellulose nanocrystal (CNC) | CNC-β-CD grafted; CNC; CNC-FA | Controlled release; CNC-β-CD maintained strong inhibition after 48h/3 washes; CNC/CNC-FA: 5.1/2.1 log reductions (24h) | β-CD grafting prolongs antibacterial activity | [173] |
| Polypropylene (PP) | 4, 6, 8 wt.% (PPC4, PPC6, PPC8) | E. coli, S. aureus (tested via agar disk diffusion) | — | [174] |
| Gelatin | 1–5% (w/w, gelatin powder basis) | B. subtilis, S. aureus (Gram-positive; greater efficacy), E. coli, P. aeruginosa | — | [156] |
| PLA (impregnated with Z. multiflora EO, 21.37 wt.% carvacrol) | 13.65–20.76 wt.% impregnation yield | E. coli, S. aureus (undetectable viability) | — | [44] |
| Electrospun PLA fibers | 5, 10, 20% | 20% carvacrol inhibited 99.6% mold growth on whole wheat bread; improved controlled release | — | [175] |
| Cellulose acetate (CA) | 10% | W. viridescens (reduced growth rate); extended ham shelf life by 10 days | Migration diffusion coefficients: 10⁻¹³–10⁻¹⁵ m²/s in food fluid simulations | [176] |
| Electrospun polycaprolactone (PCL) fiber mats | Carvacrol (60/90-min electrodeposition) | E. coli (bacteriostatic from day 2; bactericidal from day 7) | — | [177] |
| Chitosan | 20% (w/w) | P. fragi, Sh. putrefaciens (most sensitive), A. hydrophila (significant inhibition) | — | [133] |
| Cast polyester monolayer (CP(CA)) | 25 g carvacrol/100 g polymer | E. coli (9 log CFU reduction), L. innocua (5 log CFU reduction) | Released carvacrol exceeded MIC for both bacteria | [178] |
| Isonicotinamide-carvacrol (INA-CAR) cocrystals | Cocrystal formulation (vs. chitosan-coated packaging) | Enhanced inhibition (3x vs. chitosan coating); constant vapor release over 14 days | — | [113] |
Carvacrol-incorporated films also demonstrate efficacy in food preservation. Cooked ham wrapped in 10% carvacrol CA films (786 μg/mL carvacrol) extended shelf life by 9 days vs. controls, inhibiting W. viridescens and P. fluorescens [179]. Baby spinach wrapped in starch-polyvinyl alcohol-silica (SPS) nanocomposite films with 4–6% carvacrol (thyme essential oil component) showed complete microbial (bacteria, yeast, mold) inhibition at 4°C, reducing E. coli and Salmonella by >4.5 log CFU/g [180]. In meat preservation: oregano oil-based films decreased Pseudomonas (0.95 log) and E. coli O157:H7 (1.12 log) over 7 days [181]; whey-based Pickering emulsions (whey-NEO) with carvacrol-containing essential oil reduced beef total viable counts (TVC) to 6.8 log CFU/g after 18 days—lower than free essential oil (whey-EO) due to enhanced protection, reduced evaporation, and easier cell wall transfer [162]. Carvacrol-loaded microcapsules (2% tannic acid crosslinking) in olive paste prolonged protection by reducing volatility, maintaining carvacrol/thymol concentrations and inhibiting mesophilic aerobic bacteria [182].
Synergies with other components further improve performance: biodegradable starch films with carvacrol and montmorillonite synergistically inhibited E. coli via membrane destabilization [87]; PVDF nanofibers with carvacrol and cinnamaldehyde reduced bacterial aggregation [170]; EVA films with carvacrol achieved 2–3 log E. coli reductions, 2.5–4 log S. aureus reductions, and 1–2 log mixed culture reductions at 37°C (slower activity at 22°C, reduced effect at 4°C) [171]; whey protein isolate (WPI) coatings with 2.16% carvacrol delayed growth of mesophilic/psychrotrophic bacteria, Pseudomonas, Enterobacteriaceae, LAB, and H₂S-producing bacteria on hake medallions over 12 days [134]; carboxymethyl cellulose (CMC) coatings with Z. multiflora EO (65.22% carvacrol) and Mentha spicata EO reduced chicken breast TVC (4.88–5.25 log) and psychrotrophic counts (4.17–4.87 log), inhibiting L. monocytogenes, E. coli O157:H7, S. typhimurium, and C. jejuni [183]; gelatin-chitosan (GC) films with 0.4–1.0% carvacrol reduced E. coli O157:H7 (0.75 log) and L. monocytogenes (1.65 log) on ham after 9 days [184]. Sensory considerations include: 0.5% carvacrol tomato-based films did not affect cooked chicken preference (0.75% reduced preference); 0.5% carvacrol apple-based films were less preferred than cinnamaldehyde-containing films due to flavor incompatibility [172].
Carvacrol's Antibacterial Efficacy in Diverse Formulations (Creams, Sponges, Patches) for Non-Food Uses
Carvacrol has been incorporated into diverse non-food formulations—including nanoemulsion hydrogels, creams, cocrystals, essential oil-based blends, composite sponges, and patches—to enhance its antibacterial efficacy. The following table summarizes key formulations, their compositions, and observed antimicrobial activities:
Antimicrobial Activity of Carvacrol in Non-Food Formulations
| Formulation Type | Key Composition Details | Target Microorganism(s) | Activity Observation | Citation |
|---|---|---|---|---|
| Nanoemulsion hydrogel | 0.5% carvacrol; 14.6% Labrafac®WL1349; 14.6% Kolliphor®ELP; 0.5% Carbopol 940; 69.34% deionized water | Staphylococcus aureus, Gram-negative bacteria | Bactericidal activity; conventional cream with same carvacrol concentration was inactive (likely due to slower release) | [163] |
| Cream | 3 wt% carvacrol | Bacteria; Trichophyton rubrum, Candida albicans; Aspergillus niger, Penicillium chrysogenum | Large, clear bacterial inhibition zones; strong fungal inhibition; small mold inhibition zones | [185] |
| Cream | 2 wt% carvacrol | Candida albicans | Hindered development | [185] |
| Phenazine-carvacrol (PHE:CARV) cocrystal | N/A (composition not specified) | Bacillus sp. (strain B7); Cladosporium sp., Trichophyton orientale | Strongest antibacterial inhibition among tested cocrystals (comparable to pure carvacrol); complete fungal growth prevention (matching pure carvacrol) | [43] |
| Essential oil-based formulation (Phyto-Bomat) | 23.11 ± 2.31 mg/mL carvacrol | Escherichia coli, Streptococcus spp., Staphylococcus spp. (and other tested bacteria) | MIC range: 22.72–45.4 mg/mL (lowest values for E. coli, Streptococcus spp., Staphylococcus spp.) | [186] |
| Composite sponge | Carvacrol; modified ZnO; Satureja thymbra L. essential oil | Staphylococcus aureus, Escherichia coli | Enhanced antibacterial activity; samples with ZnO + essential oil had larger inhibition zones than those without | [150] |
| Patch | Carvacrol | Escherichia coli, Listeria monocytogenes | Marked antibacterial activity; significant decrease in viable counts after 3 days vs. empty patches | [187] |
Notably, formulation type and carvacrol concentration directly influenced performance: for example, a nanoemulsion hydrogel’s bactericidal activity contrasted with an inactive conventional cream at the same 0.5% carvacrol concentration, while higher carvacrol levels (3 wt%) in creams broadened antimicrobial coverage to include bacteria, fungi, and molds. Cocrystals and composite sponges further optimized efficacy through structural or additive-based enhancements, highlighting the value of formulation engineering in maximizing carvacrol’s potential for non-food antimicrobial applications.
Practical Applications of Carvacrol in Food Preservation and Animal Health
Carvacrol's Antibacterial Mechanisms: Membrane Disruption, ATP Depletion, and Biofilm Inhibition
Carvacrol, a monoterpenoid phenol and GRAS-listed compound, exhibits broad-spectrum antibacterial activity against foodborne and pathogenic bacteria, including Aeromonas hydrophila, Xanthomonas campestris pv. campestris (Xcc), Escherichia coli, Salmonella enterica, Staphylococcus aureus, Clostridium perfringens, and Bacillus cereus [137][87][68][72][73][97][136][60]. Its antibacterial mechanisms center on three key pathways: membrane disruption, ATP depletion, and biofilm inhibition, with additional synergistic effects enhancing its utility as a natural antimicrobial alternative.
Carvacrol’s Antibacterial Efficacy, Mechanistic Effects, and Applications Across Target Organisms
| Target Organism/Context | Key Effect | Concentration/Dose | Citations |
|---|---|---|---|
| Broad-spectrum bacteria | Broad antibacterial activity | Not specified | [137][87][68][73][97] |
| General membrane disruption | Integrates into lipid monolayers, reduces packing, increases fluidity, alters dipole moments | Not specified | [73] |
| General membrane disruption | Depolarizes cytoplasmic membranes, causes K+ leakage (membrane damage marker) | Not specified | [72][97] |
| Xcc | Induces visible membrane deformations within 30 minutes | 0.0195% | [68] |
| Gram-negative bacteria | Disrupts outer membrane, releases lipopolysaccharides, increases cytoplasmic permeability | Not specified | [97][60] |
| B. cereus | Depletes ATP (reduces synthesis, enhances hydrolysis); alters membrane potential/proton permeability | Not specified | [72][73][136] |
| A. hydrophila NJ-35 | Inhibitory (MIC) and bactericidal (MBC) activity | MIC: 125 µg/mL; MBC: 250 µg/mL | [137] |
| Xcc | Eliminates bacteria from cabbage seeds, eradicates mature biofilms | 0.0195% | [68] |
| C. perfringens | Inhibitory activity (MIC) | MIC: 18 µg/mL | [97] |
| A. hydrophila | Reduces biofilm formation, EPS production, protease/hemolytic activity; downregulates virulence genes (flaB, aha, ompA) | 1/4 MIC | [137] |
| S. aureus, S. enterica | Inhibits biofilm formation (as effective as commercial sanitizers) | Not specified | [73] |
| A. hydrophila | Eradicates mature biofilms (time- and dose-dependent) | Not specified | [137] |
| Food systems (rice, tomatoes, grapes, apple juice) | Controls pathogens | Not specified | [87] |
| Raw chicken surfaces | Eliminates S. enterica (vapor form) | Not specified | [73] |
| Edible films (chicken breast, ham, lettuce) | Inactivates E. coli, Salmonella, L. monocytogenes | Not specified | [73] |
| Starch films | Synergistic antimicrobial effects against E. coli | Not specified | [87] |
| Broiler diets | Improves body weight gain by 2.64% (vs. antibiotic controls) | Not specified | [97] |
| Broiler gut (with thymol/eugenol) | Reduces C. perfringens colonization | Blended with thymol and eugenol | [60] |
| Grass carp (A. hydrophila-infected) | Increases survival rate (56% vs. 24% in controls) | Not specified | [137] |
| Poultry feed | Reduces aflatoxin production by Aspergillus spp. | Not specified | [136] |
| E. coli | Reduced inhibitory concentrations (synergistic with thymol) | Combined with thymol | [87] |
| B. cereus | Improved activity (synergistic with p-cymene) | Combined with p-cymene | [60] |
Practical applications of carvacrol span food preservation and animal health, where its GRAS status supports its use as a promising natural alternative to synthetic antimicrobials. In food systems, it controls pathogens in various commodities and, when incorporated into edible films, inactivates key bacteria on meat and produce surfaces. In animal health, it enhances growth performance, reduces gut pathogen colonization, and boosts survival in infected fish. Synergistic combinations with thymol or p-cymene further reduce inhibitory concentrations against target bacteria, expanding its utility in food and animal production.
Quantitative Antibacterial Efficacy of Carvacrol: MIC, MBC, and Time-Kill Assays Across Pathogens and Matrices
The quantitative antibacterial efficacy of carvacrol spans diverse pathogens, matrices, and application contexts, with consistent dose-dependent activity and synergistic enhancements reported across studies. Its efficacy is maintained at concentrations appropriate for food flavouring (e.g., 0.18 mM/28.54 ppm in nonalcoholic beverages and 15.75 ppm in baked goods [72]) and is influenced by factors like temperature, matrix components, and combination with other compounds. For example, carvacrol exhibited higher bactericidal activity against Listeria monocytogenes (LM) at 30°C than at 10°C or 20°C [126], but binding to bovine serum albumin (BSA) and egg yolk in steak tartare nullified its effect on LM growth [126]. Synergistic combinations (e.g., with cymene [144], thymol [68], nisin [127], lauric alginate [73], or fatty acids [147]) enhanced efficacy, while carvacrol reduced radiation D₁₀ values for E. coli and Salmonella Typhi in meat samples [117]. Mechanistically, carvacrol disrupts bacterial membranes (increasing permeability, reducing lipid packing, altering dipole moment [73]), depletes intracellular ATP [73], lowers internal pH [72], and inhibits ATP synthesis [96][73].
Carvacrol Antibacterial Activity: MIC, MBC, and Efficacy Data by Pathogen and Matrix
| Pathogen/Organism | Matrix/Assay Condition | MIC/MBC/Key Efficacy Metric | Citation |
|---|---|---|---|
| E. coli (ATCC 25922), S. Typhimurium (ATCC 14028), A. hydrophila (ATCC 7966), S. aureus (ATCC 25923) | Broth microdilution (CLSI 2012) | MIC = 312 μg/ml (all) | [107] |
| P. aeruginosa ATCC 9027 | In vitro | MIC = 0.6 mL/mL | [109] |
| S. enterica sv Anatum SF2 | In vitro | MIC = 250 μg/mL | [45] |
| B. cereus | In vitro | 0.19 mg/g (slight inhibition); 0.38 mg/g (full suppression); 0.53 mg/g (viable counts < detection limit at 7 days) | [144] |
| E. coli, S. Typhimurium, A. hydrophila | Cassava starch edible coatings (minimally processed pumpkin) | 312 μg/ml: 5 log CFU/g reduction (E. coli/S. Typhimurium), ~8 log CFU/g reduction (A. hydrophila); 625 μg/ml: complete inhibition | [107] |
| Naturally present bacteria | Cassava starch edible coatings (minimally processed pumpkin) | T1/T2 groups: coliforms <3 MPN/g; T2: 1.9 log CFU/g reduction (psychrotrophs); mold/yeast <2 log CFU/g | [107] |
| Lactic acid bacteria (LAB) | Oregano EO (81.85% carvacrol) in QSMF coatings (rainbow trout fillets) | <1 log CFU/g reduction; shelf life extended to 15–18 days (vs. 7–9 days control) | [1] |
| P. aeruginosa | Ground beef (sublethal concentrations: 1/2, 1/4 MIC) | No direct/cross-tolerance to lactic acid, salt, or high temperature over 72 hours | [109] |
| Inoculated pathogens, total coliform counts (TCC), aerobic plate counts (APC) | Teriyaki sauce (0.5% carvacrol) on beef | Most pathogens inactivated by 7 days; TCC eliminated in 1 day; APC reduced by 1.2–2.8 log CFU/mL (leftover marinade) | [88] |
| Pseudomonas, E. coli O157:H7 | Oregano EO-based films (meat) | 0.95 log CFU/cm² (Pseudomonas), 1.12 log CFU/cm² (E. coli O157:H7) reduction at 7 days | [181] |
| E. coli O157:H7, Salmonella | 0.3% carvacrol (fresh herbs: basil, cilantro, dill, tarragon) | E. coli: <0.57 log CFU/g; Salmonella: ≤0.57 log CFU/g at 14 days | [188] |
| Xanthomonas campestris pv. campestris (Xcc) | In vitro, germinated cabbage seeds | MIC = 0.0098% (8 strains); 0.0195% (bactericidal at 30 min); 0.078% (eradication from seeds) | [68] |
| B. cereus | 0.5 mM carvacrol + 0.25 mM cymene | 50% viable count reduction at 48 minutes | [144] |
| Xcc | 1/16 MIC carvacrol + ¼ MIC thymol | Fractional Inhibitory Concentration Index (FICI) = 0.31 | [68] |
| E. coli, S. Typhi | In vitro | Most effective vs. tested compounds; S. Typhi more sensitive to carvacrol than thymol/thyme extract | [117] |
| E. coli, S. Typhi | Meat (radiation D₁₀ values) | E. coli: 0.126→0.057 kGy; S. Typhi: 0.519→0.235 kGy | [117] |
| Shigella sonnei, S. flexneri | In vitro | MIC = 0.1−1.0% | [73] |
| Mycobacterium avium subsp. paratuberculosis | In vitro | MIC = 72.2 μg/mL | [73] |
| E. coli, S. enterica | EO6 (91.56% carvacrol) | MIC = 0.05% v/v (both); inhibitory haloes = 2.75 cm (E. coli), 2.47 cm (S. enterica) | [99] |
| E. coli, S. enterica | 1% EO6 sanitizer | ~8 log CFU/ml inhibition at 30 sec (E. coli), 60 sec (S. enterica) | [99] |
| Mastitis pathogens (S. aureus, E. coli, Strep. uberis, Strep. agalactiae, Strep. dysgalactiae) | Milk | MIC = 0.4–0.8%; MBC = 0.8–1.5% | [124] |
| L. monocytogenes | Fresh catfish fillets (0.5% carvacrol) | 4 log CFU/mL reduction at 30 min | [131] |
| Weisella viridescens, Pseudomonas fluorescens | In vitro | MIC = 293 μg/mL (W. viridescens), 194 μg/mL (P. fluorescens); MBC = 488 μg/mL (both) | [176] |
| Brochothrix thermosphacta | Terpenes (750 mg/kg MIC carvacrol) + fatty acids (SYN) | Bacterial counts maintained at inoculation level over 2 weeks | [147] |
| S. enterica, E. coli O157:H7, L. monocytogenes | Carvacrol vapor/edible films (raw chicken, chicken breast, ham, lettuce) | Vapor eliminated S. enterica on chicken; films inactivated all pathogens | [73] |
| S. aureus, S. enterica | Carvacrol | Inhibited biofilm formation (as effective as commercial sanitizer) | [73] |
| P. aeruginosa | Thyme EO (17.4% carvacrol) (sous vide red deer meat) | Reduced total viable counts vs. untreated inoculated groups | [189] |
| P. aeruginosa, total mesophilic aerobic bacteria | Zataria multiflora EO (66.2% carvacrol) (rainbow trout fillets) | 1.5% EO: reduction over 12 days | [131] |
| L. monocytogenes | Carvacrol + nisin | Bactericidal in culture medium; enhanced inhibition in pasteurized milk | [127] |
| S. enterica | Carvacrol + lauric alginate (ground turkey) | 4 log cfu/g reduction | [73] |
| Lactobacillus curvatus | Terpenes (including carvacrol) + fatty acids (SYN) (meat model) | Specific growth rate reduced from 0.66 to 0.24 d⁻¹ | [147] |
| S. aureus, E. coli O157:H7, S. typhimurium, Serratia liquefaciens, Carnobacterium divergens, L. innocua, Shewanella putrefaciens | Thyme EO (75.27% carvacrol) (broth microdilution) | MIC = 0.05% (S. aureus/E. coli O157:H7/S. typhimurium), 0.06% (S. liquefaciens/C. divergens), 0.125% (L. innocua), 0.25% (S. putrefaciens) | [27] |
| S. typhimurium | Thyme EO (4×MIC) (minced meat, 4°C/9 days) | Initial 4 log CFU/g → ~5 log CFU/g (vs. 6 log CFU/g control) | [27] |
| L. monocytogenes (LM) | TSB (30°C) | MIC = 1.63 mM; 2.5 mM: 4-log decrease in LM after 24 h (higher activity at 30°C vs. 10/20°C) | [126] |
| E. coli O157:H7, S. Enteritidis | Carvacrol nanoemulsions (TSB) | MIC ~500 ppm; ≥4000 ppm: inactivation < detection limit | [190] |
| E. coli O157:H7, S. Enteritidis | Carvacrol nanoemulsions (mung bean/alfalfa seeds) | 4000–8000 ppm: pathogen levels ≤3 CFU/g (no germination impact) | [190] |
Additional Efficacy Data for Carvacrol Combinations and Specialized Applications
| Combination/Application | Pathogen/Matrix | Key Outcome | Citation |
|---|---|---|---|
| 0.5 mM carvacrol + 0.25 mM cymene | B. cereus | 50% viable count reduction at 48 minutes | [144] |
| Carvacrol-thymol (1/16 MIC + ¼ MIC) | Xcc | FICI = 0.31 (synergistic) | [68] |
| Carvacrol vs. thymol/thyme extract | E. coli, S. Typhi | Most effective compound; S. Typhi more sensitive to carvacrol | [117] |
| Carvacrol + nisin | L. monocytogenes | Bactericidal in culture medium; enhanced inhibition in pasteurized milk | [127] |
| Carvacrol + lauric alginate | S. enterica (ground turkey) | 4 log cfu/g reduction | [73] |
| Terpenes (including carvacrol) + fatty acids (SYN) | L. curvatus (meat model) | Specific growth rate reduced from 0.66 to 0.24 d⁻¹ | [147] |
| Thyme EO (75.27% carvacrol) (4×MIC) | S. typhimurium (minced meat, 4°C/9 days) | Initial 4 log CFU/g → ~5 log CFU/g (vs. 6 log CFU/g control) | [27] |
| Carvacrol (5 mmol/g) | L. monocytogenes (steak tartare, 10°C/4 weeks) | No growth difference vs. control (matrix binding) | [126] |
| Carvacrol nanoemulsions (4000–8000 ppm) | E. coli O157:H7, S. Enteritidis (seeds) | Pathogen levels ≤3 CFU/g (no germination impact) | [190] |
Carvacrol-Enriched Edible Coatings and Films for Food Preservation: Efficacy in Meat, Seafood, and Produce
Carvacrol-enriched edible coatings and films exhibit broad efficacy in preserving meat, seafood, and produce by inhibiting microbial growth, reducing lipid oxidation, and extending shelf life. Their applications across food categories target both spoilage and pathogenic microorganisms, with performance enhanced by formulation strategies (e.g., microencapsulation, electrospinning) and synergistic combinations with other compounds.
Antimicrobial and Shelf Life Effects of Carvacrol-Enriched Coatings/Films in Meat Preservation
| Food Product | Carvacrol Source/Formulation | Key Microbial/Lipid Oxidation Effect | Shelf Life Impact | Citation |
|---|---|---|---|---|
| Beef | Teriyaki sauce (0.5% carvacrol) | Inactivated all inoculated pathogens (except Salmonella Typhimurium); eliminated total coliforms in 1 day | — | [88] |
| Cooked ham | Cellulose acetate (CA) films (10% carvacrol, 786 μg/mL MBD) | Inhibited Weissella viridescens and Pseudomonas fluorescens | Extended by 9 days vs. controls | [179] |
| Meat | Oregano EO-based films (carvacrol-rich) | Reduced Pseudomonas (0.95 log CFU/cm²) and E. coli O157:H7 (1.12 log CFU/cm²) after 7 days | — | [181] |
| Meat (air-packed) | Carvacrol (added directly) | Reduced radiation D₁₀ value for E. coli from 0.126 ± 0.0039 kGy to 0.057 ± 0.0015 kGy | — | [117] |
| Sous vide red deer meat | Thymus daenensis EO (17.4% carvacrol) | Lowered TVC (1.17–1.75 log CFU/g); no Clostridium botulinum detected in vacuum-packaged samples | — | [189] |
| Minced meat | Thyme EO (75.27% carvacrol, 4MIC/0.2%) | Reduced Salmonella Typhimurium by ~1 log CFU/g over 9 days (4°C) | — | [27] |
| Ham | GC films (0.4–1.0% carvacrol) | Reduced E. coli O157:H7 (0.75 log CFU/g) and Listeria monocytogenes (1.65 log CFU/g) after 9 days | — | [184] |
| — | Cast polyester films (25 g carvacrol/100 g polymer, C-75:25:15-CA) | Reduced E. coli (CECT 101) by 9 log CFU and Listeria innocua (CECT 910) by 5 log CFU | — | [178] |
Antimicrobial and Shelf Life Effects of Carvacrol-Enriched Coatings/Films in Seafood Preservation
| Food Product | Carvacrol Source/Formulation | Key Microbial/Lipid Oxidation Effect | Shelf Life Impact | Citation |
|---|---|---|---|---|
| Rainbow trout fillets | Quinoa starch-based films (2% oregano EO, 81.85% carvacrol) | Reduced lactic acid bacteria (LAB) counts | Extended to 15–18 days (vs. 7–9 days controls) | [1] |
| Fish fillets | 0.5% carvacrol (direct treatment) | Reduced Listeria monocytogenes by up to 2.84 log CFU/g | — | [111] |
| Hake medallions | Whey protein isolate (WPI) films (2.16% carvacrol, 3% oregano EO equivalent) | Delayed growth of mesophilic/psychrotrophic bacteria, Pseudomonas, Enterobacteriaceae, LAB, H₂S-producing bacteria; Pseudomonas <1 log CFU/g (day 4) vs. ≥4.60 log CFU/g (controls) | — | [134] |
| Rainbow trout fillets | Zataria multiflora EO (66.2% carvacrol, 1.5% w/w + 2% potassium sorbate) | Reduced Pseudomonas aeruginosa, total mesophilic bacteria, TBARS, TVB-N; improved sensory scores | — | [131] |
| — | PLA films (Z. multiflora EO, 21.37 wt.% carvacrol) | Inhibited E. coli and S. aureus; some formulations showed no detectable viability | — | [44] |
Antimicrobial Effects of Carvacrol-Enriched Coatings/Films in Produce Preservation
| Food Product | Carvacrol Source/Formulation | Key Microbial Effect | Citation |
|---|---|---|---|
| Minimally processed pumpkin (MPP) | Cassava starch (625 μg/mL carvacrol) | Complete inhibition of E. coli, S. Typhimurium, Aeromonas hydrophila, S. aureus over 7 days; 312 μg/mL reduced E. coli/S. Typhimurium by 5 log CFU/g | [107] |
| Baby spinach | Starch-based nanocomposite films (4–6% thyme EO, carvacrol-rich) | No bacterial/yeast/mold growth; 6% TEO completely inhibited Salmonella and E. coli | [180] |
| Melon/pumpkin | Methylcellulose (MB) foams (20% carvacrol) | Reduced TMM, L. monocytogenes, P. poae by 1 log cycle in 3 days; complete disappearance by day 7 | [157] |
| Leafy greens (baby spinach, mature spinach, Iceberg/Romaine lettuce) | Apple/carrot/hibiscus films (3% carvacrol) | Reduced Salmonella to <1 log CFU/g (day 0); apple films showed 4.6/1.8 log reductions in baby spinach (days 3/7) | [132] |
| Iceberg lettuce | Carrot films (1.5% carvacrol) | Reduced Salmonella to <1 log CFU/g (day 7) | [132] |
| Iceberg lettuce | Hibiscus films (1.5% carvacrol) | 4 log reduction in Salmonella (day 7) | [132] |
| Grapes | Isonicotinamide-carvacrol (INA-CAR) cocrystals + chitosan coating | >86% microflora inhibition (days 3/7); constant vapor-phase release over 14 days | [113] |
Carvacrol’s safety (GRAS status, up to 50 mg/kg use level [87]) and mechanism of action (membrane damage, respiratory chain disruption [87][191]) support its broad applicability. Synergistic combinations enhance efficacy: carvacrol with thymol/citral reduces L. monocytogenes inhibitory concentrations by 50% [104], while carvacrol-nisin combinations show bactericidal effects against L. monocytogenes in pasteurized milk [127]. Formulation strategies improve stability and release: whey-based Pickering nanoemulsions (whey-NEO) with carvacrol-rich EO reduce TVC, pH, peroxide value (PV), TBARs, and TVB-N in beef more effectively than free EO [162]; thyme EO microcapsules in olive paste prolong antimicrobial protection via reduced carvacrol volatility [182]; electrospun PLA fibers (5–20% carvacrol) enable controlled release, with 20% carvacrol inhibiting 99.6% of mold growth in whole wheat bread [175]; and carvacrol-loaded patches inhibit E. coli, L. monocytogenes, Alternaria alternate, and Penicillium commune [187]. Carvacrol release kinetics from polyester films depend on food simulant polarity (max release in less polar simulants), influencing matrix-specific efficacy [178].
Carvacrol Applications in Animal Health: Dietary Supplements and Pathogen Control in Livestock and Aquaculture
Carvacrol, a monoterpenoid phenol recognized as Generally Recognized as Safe (GRAS) [87], has emerged as a promising multifunctional agent for pathogen control, performance enhancement, and gut health modulation in livestock and aquaculture. Its efficacy spans poultry, swine, and aquatic species, with synergistic effects often observed when combined with other phytochemicals or antibiotics, though dosage optimization is critical to avoid adverse outcomes.
Carvacrol Efficacy in Livestock and Aquaculture: Pathogen Control, Growth, and Gut Health Outcomes
| Species/System | Carvacrol Formulation/Dosage | Key Outcome(s) | Citation(s) |
|---|---|---|---|
| Poultry (Broilers) | 1% in feed | Reduced Campylobacter jejuni in cecal samples post-challenge | [45] |
| Poultry (Broilers) | 300 or 400 μl doses | Significantly decreased intestinal Escherichia coli and Salmonella counts | [192] |
| Poultry (Broilers) | Blend: 0.5% carvacrol + 0.5% thymol | Reduced C. jejuni colonization | [45] |
| Poultry (Broilers) | Microencapsulated: 5% carvacrol + 5% cinnamaldehyde | Improved feed conversion and growth | [193] |
| Poultry (Broilers) | 300 or 400 μl doses | Increased intestinal sucrase and lactase activity | [192] |
| Poultry (Broilers) | Phytogenic feed additive (PFA): carvacrol + thymol + cinnamic aldehyde | Decreased total bacterial counts at 42 days | [194] |
| Swine (Weaned Pigs) | 100 mg/kg carvacrol | Increased jejunal villus height; reduced serum inflammatory marker (IL-6) | [193] |
| Swine (Weaned Pigs) | 100 mg/kg carvacrol | Elevated serum ghrelin levels (potential feed intake stimulation) | [193] |
| Swine | 10% microencapsulated carvacrol (0.1% in diet) | Reduced diarrhea rates across 42 days | [193] |
| Aquaculture (Fish) | 125 μg/mL (MIC) / 250 μg/mL (MBC) | Inhibited Aeromonas hydrophila NJ-35; sub-MIC (1/4 MIC) reduced virulence gene expression (flaB, aha) and biofilm formation | [137] |
| Aquaculture (Gilthead Seabream) | 0.5% microencapsulated carvacrol + garlic EO + thymol | Enhanced skin mucus-mediated inhibition of Vibrio anguillarum and Photobacterium anguilliseptica growth | [168] |
| Aquaculture (Shrimp) | 2 g/kg diet (carvacrol-containing EO blend) | Reduced cumulative mortality (40% vs. 66.7% control) and total Vibrio in hepatopancreas | [195] |
| Dairy Calves | Carvacrol-containing EO blend (milk replacer) | Shifted rumen microbiome: reduced Firmicutes (Lachnospiraceae) and increased Bacteroidetes (Prevotellaceae) | [196] |
| Meat Quality (Broilers) | Carvacrol supplementation | Reduced tissue lipid oxidation | [87] |
| Meat Quality (Broilers) | Origanum majorana EO (3.7% carvacrol) | Improved weight gain vs. antibiotic-fed controls | [97] |
| Antibacterial Mechanism | Carvacrol + p-cymene (biological precursor) | Synergism against B. cereus vegetative cells (p-cymene swells cell membranes for easier carvacrol transport) | [60] |
| Antibacterial Mechanism | Carvacrol-containing essential oils (EOs) | Phenolic components drive antibacterial properties | [60] |
| Antibacterial Mechanism | Carvacrol + thymol + eugenol + curcumin + piperin | Reduced C. perfringens colonization/proliferation in broiler gut | [60] |
| Antibacterial Mechanism | Carvacrol + capsicum + cinnamaldehyde | Lowered E. coli and C. perfringens in broilers | [60] |
| Synergy (Antibiotics) | Thymus maroccanus EO (76.35% carvacrol) + ciprofloxacin/gentamicin/pristinamycin | Synergism against bacterial pathogens | [45] |
| Synergy (Antibiotics) | Thymus saturejoides EO (25.3–45.3% carvacrol) + cefixime | Synergism against Klebsiella pneumoniae | [45] |
| Synergy (Phytochemicals) | Carvacrol + thymol | Decreased Salmonella Typhimurium biofilm mass | [87] |
| Adverse Effect | 50 μg/kg in ovo (high dose) | Impaired embryonic development | [197] |
| Adverse Effect | Carvacrol intake (broilers) | Negative correlation with 42-day body weight | [198] |
The phenolic components of carvacrol-containing essential oils (EOs) are primarily responsible for their antibacterial properties [60], with synergistic interactions targeting multiple bacterial pathways (e.g., membrane integrity, enzyme function, DNA synthesis) [45]. Beyond pathogen control, carvacrol supports digestive function and gut microbiome balance—for example, modulating rumen microbiota in dairy calves [196] and altering intestinal bacterial community clustering in broilers via Origanum vulgare ssp. hirtum EO (50.8% carvacrol) [198]. Its anti-biofilm properties are critical for persistent pathogen control: sub-minimum inhibitory concentration (MIC) carvacrol reduced extracellular polymeric substance (EPS) production and mature biofilm biomass in A. hydrophila [137], while carvacrol-thymol combinations decreased Salmonella Typhimurium biofilm mass [87].
Collectively, these findings support carvacrol’s role in sustainable pathogen management and production efficiency in animal agriculture. However, high doses (e.g., 50 μg/kg in ovo [197]) or unbalanced inclusion (linked to reduced broiler body weight [198]) highlight the need for careful dosage optimization to maximize benefits while avoiding harm.
Synergistic and Formulation-Enhanced Antibacterial Activity of Carvacrol: Combinations, Nanoemulsions, and Microencapsulation
Carvacrol demonstrates potent antibacterial activity against Gram-positive and Gram-negative pathogens, with mechanisms including membrane damage, respiratory chain disruption, reduced ATP synthesis, and increased cytoplasmic membrane porosity [87][199]. Its efficacy varies by application context—from essential oil (EO) constituents to synergistic combinations and formulated delivery systems—as detailed below.
Carvacrol Antibacterial Efficacy: Single-Agent and EO Constituent Applications
| Pathogen | Carvacrol Formulation | Concentration | Outcome | Citation |
|---|---|---|---|---|
| Salmonella enterica sv Anatum SF2 | Main constituent of Satureja montana EO (825.0–950.0 μg/mg) | 250 μg/mL | In vitro MIC | [45] |
| Bacillus cereus | Single agent | 0.38 mg/g | Full growth suppression; ≥0.53 mg/g reduced viable counts below detection limit within 7 days | [144] |
| Staphylococcus aureus, Listeria monocytogenes, Salmonella Enteritidis | Constituent of Mexican oregano EO | 0.15–0.40% (vol/vol) | Growth inhibition | [7] |
| Xanthomonas campestris pv. campestris (Xcc) | 0.0195% solution | 0.0195% | Bactericidal effect; membrane deformations within 30 minutes | [68] |
| Campylobacter jejuni (broiler chicks) | Dietary supplementation | 1% (single agent) or 0.5% (thymol-carvacrol combination) | Reduced cecal counts | [45] |
Synergistic combinations enhance carvacrol’s efficacy by targeting multiple bacterial pathways. For example, 0.5 mM carvacrol + 0.25 mM cymene reduced Bacillus cereus viable counts to 50% of initial levels within 48 minutes [144]; p-cymene (a weak antibacterial) swells cell membranes to facilitate carvacrol uptake [60]. Thymus maroccanus EO (76.35% carvacrol) synergized with ciprofloxacin, gentamicin, and pristinamycin via combined action on membrane, protein, enzyme, ATP, and DNA targets [45]. A 1:1 carvacrol-thymol blend reduced Lactobacillus curvatus specific growth rate by 63.3% in a meat model [147], while 0.0097% carvacrol + 0.039% thymol eradicated Xcc from germinated cabbage plants [68]. Additional synergies include carvacrol + nisin against L. monocytogenes in pasteurized milk [127], carvacrol + montmorillonite in starch films against Escherichia coli (membrane destabilization) [87], and blended EOs (thymol/eugenol/curcumin/piperin ± carvacrol) reducing Clostridium perfringens colonization in broilers [60]. A capsicum/cinnamaldehyde/carvacrol blend also lowered E. coli and C. perfringens counts [60].
Carvacrol Antibacterial Efficacy: Formulated Delivery Systems
| Formulation | Application | Concentration | Outcome | Citation |
|---|---|---|---|---|
| Whey-based Pickering nanoemulsion (carvacrol-rich EO) | Beef samples | — | TVC reduced to 6.8 log CFU/g after 18 days (vs. 7 log CFU/g for free EO) | [162] |
| Microencapsulated carvacrol-containing EO (gum Arabic-gelatin + tannic acid cross-linking) | Olive paste | 172.25–473.25 mg/kg | Maintained lower mesophilic aerobic bacteria counts than free EO over 56 days; 36.39% loading capacity | [182] |
| Microencapsulated carvacrol-containing EO | — | — | 4-fold lower MBC for E. coli; 2-fold lower MBC for Pseudomonas aeruginosa and S. aureus | [160] |
| PLA_PHB films with 10 wt% carvacrol + oleic acid (OLA) | — | 10 wt% | Enhanced bactericidal activity against S. aureus and E. coli (maintained 24 hours post-incubation) | [42] |
| Carvacrol nanoemulsion | In vitro (TSB broth) against Salmonella Enteritidis and E. coli O157:H7 | ≈500 ppm (MIC); ≥4000 ppm | Inactivation below detection limit at ≥4000 ppm | [190] |
| Carvacrol nanoemulsion | Mung bean seeds (initial inoculum ≤3 log CFU/g) | 4000 or 8000 ppm | Final pathogen levels ≤3 CFU/g; no detection post-germination | [190] |
| Carvacrol nanoemulsion | Alfalfa seeds (initial inoculum ≤3 log CFU/g) | 8000 ppm (30/60 min) or 4000 ppm (60 min) | Final pathogen levels ≤3 CFU/g; no detection post-germination | [190] |
Formulation strategies (e.g., nanoemulsions, microencapsulation) improve carvacrol’s stability, delivery, and performance while addressing sensory limitations: nanoemulsions enable food use without compromising taste or aroma [200]. For instance, whey-based Pickering nanoemulsions protected carvacrol from evaporation and enhanced bacterial cell wall penetration [162], while microencapsulation extended antimicrobial protection in olive paste [182]. A carvacrol nanoemulsion also preserved total sprout yield in mung bean and alfalfa seed treatments [190].
References
[1] Jouki, M.; Tabatabaee Yazdi, F.T.; Mortazavia, S.A.; Koocheki, A.; Khazaei, N., Effect of quince seed mucilage edible films incorporated with oregano or thyme essential oil on shelf life extension of refrigerated rainbow trout fillets, 2014.0, International Journal of Food Microbiology
[2] Anastasiou TI, Mandalakis M, Krigas N, Vézignol T, Lazari D, Katharios P, Dailianis T, Antonopoulou E., Comparative Evaluation of Essential Oils from Medicinal-Aromatic Plants of Greece: Chemical Composition, Antioxidant Capacity and Antimicrobial Activity against Bacterial Fish Pathogens, 2019.0, Molecules
[3] Tohidi, Behnaz; Rahimmalek, Mehdi; Arzani, Ahmad, Essential oil composition, total phenolic, flavonoid contents, and antioxidant activity of Thymus species collected from different regions of Iran, 2017.0, FOOD CHEMISTRY
[4] Kosakowska, Olga; Weglarz, Zenon; Pioro-Jabrucka, Ewelina; Przybyl, Jaroslaw L.; Krasniewska, Karolina; Gniewosz, Malgorzata; Baczek, Katarzyna, Antioxidant and Antibacterial Activity of Essential Oils and Hydroethanolic Extracts of Greek Oregano (O. vulgare L. subsp. hirtum (Link) Ietswaart) and Common Oregano (O. vulgare L. subsp. vulgare), 2021.0, MOLECULES
[5] Rezvanpanah S, Rezaei K, Golmakani MT, Razavi SH., ANTIBACTERIAL PROPERTIES AND CHEMICAL CHARACTERIZATION OF THE ESSENTIAL OILS FROM SUMMER SAVORY EXTRACTED BY MICROWAVE-ASSISTED HYDRODISTILLATION, 2011.0, Braz J Microbiol
[6] Uysal, Burcu; Gencer, Aysegul; Oksal, Birsen S., Comparative Antibacterial, Chemical and Morphological Study of Essential Oils of Thymbra spicata var. Spicata Leaves by Solvent-Free Microwave Extraction and Hydro-Distillation, 2015.0, INTERNATIONAL JOURNAL OF FOOD PROPERTIES
[7] Reyes-Jurado, F.; López-Malo, A.; Palou, E., Antimicrobial Activity of Individual and Combined Essential Oils against Foodborne Pathogenic Bacteria, 2016.0, Journal of Food Protection
[8] Elahian F, Garshasbi M, Mehri Asiabar Z, Gholamian Dehkordi N, Yazdinezhad A, Mirzaei SA., Ecotypic Variations Affected the Biological Effectiveness of Thymus daenensis Celak Essential Oil, 2021.0, Evid Based Complement Alternat Med
[9] Dzamic, A. M.; Nikolic, B. J.; Giweli, A. A.; Mitic-Culafic, D. S.; Sokovic, M. D.; Ristic, M. S.; Knezevic-Vukcevic, J. B.; Marin, P. D., Libyan Thymus capitatus essential oil: antioxidant, antimicrobial, cytotoxic and colon pathogen adhesion-inhibition properties, 2015.0, JOURNAL OF APPLIED MICROBIOLOGY
[10] Piasecki B, Balázs VL, Kieltyka-Dadasiewicz A, Szabó P, Kocsis B, Horváth G, Ludwiczuk A., Microbiological Studies on the Influence of Essential Oils from Several Origanum Species on Respiratory Pathogens, 2023.0, Molecules
[11] Skočibušić, M.; Bezić, N.; Dunkic̈, V., Phytochemical composition and antimicrobial activities of the essential oils from Satureja subspicata Vis. growing in Croatia, 2006.0, Food Chemistry
[12] Gürsoy, U.K.; Gürsoy, M.; Gursoy, O.V.; Çakmakçi, L.; Könönen, E.; Uitto, V.-J., Anti-biofilm properties of Satureja hortensis L. essential oil against periodontal pathogens, 2009.0, Anaerobe
[13] Wijesundara, N.M.; Rupasinghe, H.P.V., Essential oils from Origanum vulgare and Salvia officinalis exhibit antibacterial and anti-biofilm activities against Streptococcus pyogenes, 2018.0, Microbial Pathogenesis
[14] Boziaris, I.S.; Chorianopoulos, N.G.; Haroutounian, S.A.; Nychas, G.-J.E., Effect of Satureja thymbra Essential Oil on Growth–No Growth Interfaces of Listeria monocytogenes Scott A and Salmonella Enteritidis PT4, at Various Temperatures, pH, and Water Activities, 2011.0, Journal of Food Protection
[15] Teixeira, Barbara; Marques, Antonio; Ramos, Cristina; Serrano, Carmo; Matos, Olivia; Neng, Nuno R.; Nogueira, Jose M. F.; Saraiva, Jorge Alexandre; Nunes, Maria Leonor, Chemical composition and bioactivity of different oregano (Origanum vulgare) extracts and essential oil, 2013.0, JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE
[16] Park SY, Raka RN, Hui XL, Song Y, Sun JL, Xiang J, Wang J, Jin JM, Li XK, Xiao JS, Wu H., Six Spain Thymus essential oils composition analysis and their in vitro and in silico study against Streptococcus mutans, 2023.0, BMC Complement Med Ther
[17] Marinkovic, J.; Mitić-Ćulafić, D.M.; Nikolić, B.; Vuletić, S.; Marković, T.; Tasić, G.; Ćirić, A.; Markovic, D., Antimicrobial potential of irrigants based on essential oils of Cymbopogon martinii and Thymus zygis towards in vitro multispecies biofilm cultured in ex vivo root canals, 2020.0, Archives of Oral Biology
[18] Esen, Guelden; Azaz, Ayse Dilek; Kurkcuoglu, Mine; Baser, Kemal Husnu Can; Tinmaz, Ahmet, Essential oil and antimicrobial activity of wild and cultivated Origanum vulgare L. subsp. hirtum (Link) Ietswaart from the Marmara region, Turkey, 2007.0, FLAVOUR AND FRAGRANCE JOURNAL
[19] Bugayong, Adrienne Marrie; Cruz, Philip; Padilla, Philip Ian, Antibacterial Activity and Chemical Composition of Essential Oils from Leaves of Some Aromatic Plants of Philippines, 2019.0, JOURNAL OF ESSENTIAL OIL BEARING PLANTS
[20] Nezhadasad Aghbash, B.; Dehghan, G.; Movafeghi, A.; Talebpour, A.H.; Pouresmaeil, M.; Maggi, F.; Sabzi-Nojadeh, M., Chemical compositions and biological activity of essential oils from four populations of Satureja macrantha C.A.Mey, 2021.0, Journal of Essential Oil Research
[21] Getahun, T.; Sharma, V.; Gupta, N., Chemical Composition and Biological Activity of Essential Oils from Aloe debrana roots, 2020.0, Journal of Essential Oil-Bearing Plants
[22] Halevas, E.; Nday, C.M.; Chatzigeorgiou, E.; Varsamis, V.; Eleftheriadou, D.; Jackson, G.E.; Litsardakis, G.; Lazari, D.; Ypsilantis, K.; Salifoglou, A., Chitosan encapsulation of essential oil "cocktails" with well-defined binary Zn(II)-Schiff base species targeting antibacterial medicinal nanotechnology, 2017.0, Journal of Inorganic Biochemistry
[23] Aminkhani, Ali; Sharifi, Roholah; Dorosti, Reza, Chemical composition and antimicrobial activity of Achillea tenuifolia Lam. essential oil at different phenological stages from Khoy, 2020.0, CHEMISTRY & BIODIVERSITY
[24] Szczepanik, M.; Walczak, M.; Zawitowska, B.; Michalska-Sionkowska, M.; Szumny, A.; Wawrzeńczyk, C.; Swiontek-Brzezinska, M.S., Chemical composition, antimicrobial and insecticidal activity against the lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) of Origanum vulgare L. ssp. hirtum (Link) and Artemisia dracunculus L. essential oils, 2018.0, Journal of the Science of Food and Agriculture
[25] Serrano, C.; Matos, O.; Teixeira, B.; Ramos, C.; Neng, N.; Nogueira, J.; Nunes, M.L.; Marques, A., Antioxidant and antimicrobial activity of Satureja montana L. extracts, 2011.0, Journal of the Science of Food and Agriculture
[26] Fadil, M.; Fikri-Benbrahim, K.; Rachiq, S.; Ihssane, B.; Lebrazi, S.; Chraibi, M.; Haloui, T.; Farah, A., Combined treatment of Thymus vulgaris L., Rosmarinus officinalis L. and Myrtus communis L. essential oils against Salmonella typhimurium: Optimization of antibacterial activity by mixture design methodology, 2018.0, European Journal of Pharmaceutics and Biopharmaceutics
[27] Zengin, Hatice; Baysal, Ayse Handan, ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF THYME AND CLOVE ESSENTIAL OILS AND APPLICATION IN MINCED BEEF, 2015.0, JOURNAL OF FOOD PROCESSING AND PRESERVATION
[28] Sultanbawa, Y.; Cusack, A.; Currie, M.; Davis, C., AN INNOVATIVE MICROPLATE ASSAY TO FACILITATE THE DETECTION OF ANTIMICROBIAL ACTIVITY IN PLANT EXTRACTS, 2009.0, JOURNAL OF RAPID METHODS AND AUTOMATION IN MICROBIOLOGY
[29] Khalil N, El-Jalel L, Yousif M, Gonaid M., Altitude impact on the chemical profile and biological activities of Satureja thymbra L. essential oil, 2020.0, BMC Complement Med Ther
[30] Rivero-Cruz, I.; Duarte, G.; Navarrete, A.; Bye, R.; Linares, E.; Mata, R., Chemical Composition and Antimicrobial and Spasmolytic Properties of Poliomintha longiflora and Lippia graveolens Essential Oils, 2011.0, Journal of Food Science
[31] Aboukhalid, K.; Abdeslam, A.; Agacka-Mołdoch, M.; Doroszewska, T.; Douaik, A.; Bakha, M.; Casanova, J.; Tomi, F.; MacHon, N.; Faiz, C.A., Chemical polymorphism of Origanum compactum grown in all natural habitats in Morocco, 2016.0, Chemistry and Biodiversity
[32] Karagozlu, Meltem; Ocak, Bugra; Ozdestan-Ocak, Ozgul, Effect of Tannic Acid Concentration on the Physicochemical, Thermal, and Antioxidant Properties of Gelatin/Gum Arabic–Walled Microcapsules Containing Origanum onites L. Essential Oil, 2021.0, FOOD AND BIOPROCESS TECHNOLOGY
[33] Verma, R.S.; Chandra Padalia, R.C.; Saikia, D.; Chauhan, A.; Krishna, V., Antibacterial Activity of Origanum vulgare L. Populations of Indian origin, 2012.0, Journal of Biologically Active Products from Nature
[34] Sidiropoulou E, Marugán-Hernández V, Skoufos I, Giannenas I, Bonos E, Aguiar-Martins K, Lazari D, Papagrigoriou T, Fotou K, Grigoriadou K, Blake DP, Tzora A., In Vitro Antioxidant, Antimicrobial, Anticoccidial, and Anti-Inflammatory Study of Essential Oils of Oregano, Thyme, and Sage from Epirus, Greece, 2022.0, Life (Basel)
[35] Li F, Wang C, Xu J, Wang X, Cao M, Wang S, Zhang T, Xu Y, Wang J, Pan S, Hu W., Evaluation of the antibacterial activity of Elsholtzia ciliate essential oil against halitosis-related Fusobacterium nucleatum and Porphyromonas gingivalis, 2023.0, Front Microbiol
[36] Lopez, Patricia; Sanchez, Cristina; Batlle, Ramon; Nerin, Cristina, Vapor-Phase Activities of Cinnamon, Thyme, and Oregano Essential Oils and Key Constituents against Foodborne Microorganisms, 2007.0, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
[37] Ali-Shtayeh, Mohammed S.; Jamous, Rana M.; Abu-Zaitoun, Salam Y.; Akkawi, Rola J.; Kalbouneh, Samer R.; Dudai, Nativ; Bernstein, Nirit, Secondary treated effluent irrigation did not impact chemical composition, and enzyme inhibition activities of essential oils from Origanum syriacum var. syriacum, 2018.0, INDUSTRIAL CROPS AND PRODUCTS
[38] Kouravand, F.; Jooyandeh, H.; Barzegar, H.; Hojjati, M., Characterization of cross-linked whey protein isolate-based films containing Satureja Khuzistanica Jamzad essential oil, 2018.0, Journal of Food Processing and Preservation
[39] Vitanza, L.; Maccelli, A.; Marazzato, M.; Scazzocchio, F.; Comanducci, A.; Fornarini, S.; Crestoni, M.E.; Filippi, A.; Fraschetti, C.; Rinaldi, F.; Aleandri, M.; Goldoni, P.; Conte, M.P.; Ammendolia, M.G.; Longhi, C., Satureja montana L. essential oil and its antimicrobial activity alone or in combination with gentamicin, 2019.0, Microbial Pathogenesis
[40] Kovacevic, Zorana; Radinovic, Miodrag; Cabarkapa, Ivana; Kladar, Nebojsa; Bozin, Biljana, Natural Agents against Bovine Mastitis Pathogens, 2021.0, ANTIBIOTICS-BASEL
[41] Santamarta S, Aldavero AC, Rojo MA., Essential oil of Cymbopogon martini, source of geraniol, as a potential antibacterial agent against Bacillus subtilis, a pathogen of the bakery industry, 2021.0, F1000Res
[42] Burgos, Nuria; Armentano, Ilaria; Fortunati, Elena; Dominici, Franco; Luzi, Francesca; Fiori, Stefano; Cristofaro, Francesco; Visai, Livia; Jimenez, Alfonso; Kenny, Jose M., Functional Properties of Plasticized Bio-Based Poly(Lactic Acid)_Poly(Hydroxybutyrate) (PLA_PHB) Films for Active Food Packaging, 2017.0, FOOD AND BIOPROCESS TECHNOLOGY
[43] Menicucci, F.; Palagano, E.; Michelozzi, M.; Cencetti, G.; Raio, A.; Bacchi, A.; Mazzeo, P.P.; Cuzman, O.A.; Sidoti, A.; Guarino, S.; Basile, S.; Riccobono, O.; Peri, E.; Vizza, F.; Ienco, A., Effects of trapped-into-solids volatile organic compounds on paper biodeteriogens, 2022.0, International Biodeterioration and Biodegradation
[44] Saadati Ardestani, N.; Rojas, A.; Esfandiari, N.; Galotto, M.J.; Babhadiashar, A.; Ali Sajadian, S.A., Supercritical Fluid Extraction from Zataria multiflora Boiss and Impregnation of Bioactive Compounds in PLA for the Development of Materials with Antibacterial Properties, 2022.0, Processes
[45] Lupia C, Castagna F, Bava R, Naturale MD, Zicarelli L, Marrelli M, Statti G, Tilocca B, Roncada P, Britti D, Palma E., Use of Essential Oils to Counteract the Phenomena of Antimicrobial Resistance in Livestock Species, 2024.0, Antibiotics (Basel)
[46] Tsitlakidou, Petroula; Papachristoforou, Alexandros; Tasopoulos, Nikolaos; Matzara, Aikaterini; Hatzikamari, Magdalini; Karamanoli, Katerina; Mourtzinos, Ioannis, Sensory analysis, volatile profiles and antimicrobial properties of Origanum vulgare L. essential oils, 2021.0, FLAVOUR AND FRAGRANCE JOURNAL
[47] Rezende, D. A. d C. S.; Oliveira, C. D.; Batista, L. R.; Ferreira, V. R. F.; Brandao, R. M.; Caetano, A. R. S.; Alves, M. V. P.; Cardoso, M. G., Bactericidal and antioxidant effects of essential oils from Satureja montana L., Myristica fragrans H. and Cymbopogon flexuosus, 2022.0, LETTERS IN APPLIED MICROBIOLOGY
[48] Moumni S, Elaissi A, Trabelsi A, Merghni A, Chraief I, Jelassi B, Chemli R, Ferchichi S., Correlation between chemical composition and antibacterial activity of some Lamiaceae species essential oils from Tunisia, 2020.0, BMC Complement Med Ther
[49] Beicu, Rodica; Alexa, Ersilia; Obistioiu, Diana; Cocan, Ileana; Imbrea, Florin; Pop, Georgeta; Circioban, Denisa; Moisa, Cristian; Lupitu, Andreea; Copolovici, Lucian; Copolovici, Dana Maria; Imbrea, Ilinca Merima, Antimicrobial Potential and Phytochemical Profile of Wild and Cultivated Populations of Thyme (Thymus sp.) Growing in Western Romania, 2021.0, PLANTS-BASEL
[50] Antih, Julien; Houdkova, Marketa; Urbanova, Klara; Kokoska, Ladislav, Antibacterial Activity of Thymus vulgaris L. Essential Oil Vapours and Their GC/MS Analysis Using Solid-Phase Microextraction and Syringe Headspace Sampling Techniques, 2021.0, MOLECULES
[51] Bassolé IH, Lamien-Meda A, Bayala B, Tirogo S, Franz C, Novak J, Nebié RC, Dicko MH., Composition and Antimicrobial Activities of Lippia multiflora Moldenke, Mentha x piperita L. and Ocimum basilicum L. Essential Oils and Their Major Monoterpene Alcohols Alone and in Combination, 2010.0, Molecules
[52] Benameur, Qada; Gervasi, Teresa; Pellizzeri, Vito; Pluchtova, Maria; Grulova, Daniela; Cicero, Nicola; Meriem-Hind, Benmahdi, Comparison of sensitivity to a commercial Origanum vulgare essential oil between extended-spectrum β-lactamases (ESBL-) and non-ESBL-producing Enterobacteriaceae isolates, 2021.0, NATURAL PRODUCT RESEARCH
[53] Ersanli C, Tzora A, Skoufos I, Fotou K, Maloupa E, Grigoriadou K, Voidarou CC, Zeugolis DI., The Assessment of Antimicrobial and Anti-Biofilm Activity of Essential Oils against Staphylococcus aureus Strains, 2023.0, Antibiotics (Basel)
[54] Gómez-Sequeda N, Cáceres M, Stashenko EE, Hidalgo W, Ortiz C., Antimicrobial and Antibiofilm Activities of Essential Oils against Escherichia coli O157:H7 and Methicillin-Resistant Staphylococcus aureus (MRSA), 2020.0, Antibiotics (Basel)
[55] Martínez A, Manrique-Moreno M, Klaiss-Luna MC, Stashenko E, Zafra G, Ortiz C., Effect of Essential Oils on Growth Inhibition, Biofilm Formation and Membrane Integrity of Escherichia coli and Staphylococcus aureus, 2021.0, Antibiotics (Basel)
[56] Estaji, Ahmad; Roosta, Hamid Reza; Rezaei, Seyed Amin; Hosseini, Seyedh Saeedeh; Niknam, Fatemeh, Morphological, physiological and phytochemical response of different Satureja hortensis L. accessions to salinity in a greenhouse experiment, 2018.0, JOURNAL OF APPLIED RESEARCH ON MEDICINAL AND AROMATIC PLANTS
[57] Bejaoui, Afef; Chaabane, Hedia; Jemli, Maroua; Boulila, Abdennacer; Boussaid, Mohamed, Essential Oil Composition and Antibacterial Activity of Origanum vulgare subsp. glandulosum Desf. at Different Phenological Stages, 2013.0, JOURNAL OF MEDICINAL FOOD
[58] Kostic, Marina; Ivanov, Marija; Markovic, Tatjana; Sankovic Babic, Snezana; Barros, Lillian; Calhelha, Ricardo; Sokovic, Marina; Ciric, Ana, An in vitro study of the origanum minutiflorum O. Schwarz & P. H. Davis and Coriandrum sativum L. essential oils as chronic tonsillitis therapeutics: antibacterial, antibiofilm, antioxidant, and cytotoxic activities, 2022.0, JOURNAL OF ESSENTIAL OIL RESEARCH
[59] Maggio, Francesca; Lauteri, Carlotta; Rossi, Chiara; Ferri, Gianluigi; Serio, Annalisa; Vergara, Alberto; Paparella, Antonello, Combined effect of Tetracycline compounds and essential oils on antimicrobial resistant Salmonella enterica isolated from the swine food chain, 2025.0, FRONTIERS IN MICROBIOLOGY
[60] Brenes, A.; Roura, E., Essential oils in poultry nutrition: Main effects and modes of action, 2010.0, Animal Feed Science and Technology
[61] Caillet, S.; Lacroix, M., Effect of Gamma Radiation and Oregano Essential Oil on Murein and ATP Concentration of Listeria monocytogenes, 2006.0, Journal of Food Protection
[62] Scandorieiro S, Rodrigues BCD, Nishio EK, Panagio LA, de Oliveira AG, Durán N, Nakazato G, Kobayashi RKT., Biogenic Silver Nanoparticles Strategically Combined With Origanum vulgare Derivatives: Antibacterial Mechanism of Action and Effect on Multidrug-Resistant Strains, 2022.0, Front Microbiol
[63] Wijesundara, Niluni M.; Lee, Song F.; Cheng, Zhenyu; Davidson, Ross; Rupasinghe, H. P. Vasantha, Carvacrol exhibits rapid bactericidal activity against Streptococcus pyogenes through cell membrane damage, 2021.0, SCIENTIFIC REPORTS
[64] Mechmechani S, Gharsallaoui A, Fadel A, El Omari K, Khelissa S, Hamze M, Chihib NE., Microencapsulation of carvacrol as an efficient tool to fight Pseudomonas aeruginosa and Enterococcus faecalis biofilms, 2022.0, PLoS One
[65] de Sousa Guedes, J.P.; Torres, R.A.; de Azerêdo, G.A.; de Figueiredo, R.C.B.Q.; Vasconcelos Araújo, M.A.S.; de Souza, E.L., Carvacrol and 1,8-cineole alone or in combination at sublethal concentrations induce changes in the cell morphology and membrane permeability of Pseudomonas fluorescens in a vegetable-based broth, 2012.0, International Journal of Food Microbiology
[66] Kothalawala SG, Zhang J, Wang Y, Yu C., Submicron-Sized Vermiculite Assisted Oregano Oil for Controlled Release and Long-Term Bacterial Inhibition, 2021.0, Antibiotics (Basel)
[67] Inamuco, Jeanine; Veenendaal, Andreas K. J.; Burt, Sara A.; Post, Jan A.; Tjeerdsma-van Bokhoven, Johanna L. M.; Haagsman, Henk P.; Veldhuizen, Edwin J. A., Sub-lethal levels of carvacrol reduce Salmonella Typhimurium motility and invasion of porcine epithelial cells, 2012.0, VETERINARY MICROBIOLOGY
[68] Hakalová E, Čechová J, Tekielska DA, Eichmeier A, Pothier JF., Combined effect of thyme and clove phenolic compounds on Xanthomonas campestris pv. campestris and biocontrol of black rot disease on cabbage seeds, 2022.0, Front Microbiol
[69] Veldhuizen, EJA; Tjeerdsma-Van Bokhoven, JLM; Zweijtzer, C; Burt, SA; Haagsman, HP, Structural Requirements for the Antimicrobial Activity of Carvacrol, 2006.0, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
[70] Granata G, Stracquadanio S, Leonardi M, Napoli E, Malandrino G, Cafiso V, Stefani S, Geraci C., Oregano and Thyme Essential Oils Encapsulated in Chitosan Nanoparticles as Effective Antimicrobial Agents against Foodborne Pathogens †, 2021.0, Molecules
[71] Cristani, Mariateresa; D'Arrigo, Manuela; Mandalari, Giuseppina; Castelli, Francesco; Sarpietro, Maria Grazia; Micieli, Dorotea; Venuti, Vincenza; Bisignano, Giuseppe; Saija, Antonella; Trombetta, Domenico, Interaction of Four Monoterpenes Contained in Essential Oils with Model Membranes: Implications for Their Antibacterial Activity, 2007.0, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
[72] Başer, K.H.C., Biological and Pharmacological Activities of Carvacrol and Carvacrol Bearing Essential Oils, 2008.0, Current Pharmaceutical Design
[73] Friedman, Mendel, Chemistry and Multibeneficial Bioactivities of Carvacrol (4-Isopropyl-2-methylphenol), a Component of Essential Oils Produced by Aromatic Plants and Spices, 2014.0, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
[74] Ayari, Samia; Dussault, Dominic; Hayouni, El Akrem; Hamdi, Moktar; Lacroix, Monique, Radiation tolerance of Bacillus cereus pre-treated with carvacrol alone or in combination with nisin after exposure to single and multiple sub-lethal radiation treatment, 2013.0, FOOD CONTROL
[75] Requena, Raquel; Vargas, Maria; Chiralt, Amparo, Study of the potential synergistic antibacterial activity of essential oil components using the thiazolyl blue tetrazolium bromide (MTT) assay, 2019.0, LWT-FOOD SCIENCE AND TECHNOLOGY
[76] Hernández-Hernández E, Regalado-González C, Vázquez-Landaverde P, Guerrero-Legarreta I, García-Almendárez BE., Microencapsulation, Chemical Characterization, and Antimicrobial Activity of Mexican (Lippia graveolens H.B.K.) and European (Origanum vulgare L.) Oregano Essential Oils, 2014.0, ScientificWorldJournal
[77] Pirintsos SA, Bariotakis M, Kampa M, Sourvinos G, Lionis C, Castanas E., The Therapeutic Potential of the Essential Oil of Thymbra capitata (L.) Cav., Origanum dictamnus L. and Salvia fruticosa Mill. And a Case of Plant-Based Pharmaceutical Development, 2020.0, Front Pharmacol
[78] Lambert, RJW; Skandamis, PN; Coote, PJ; Nychas, GJE, A study of the minimum inhibitory concentration and mode of action of oregano essential oil, thymol and carvacrol, 2001.0, JOURNAL OF APPLIED MICROBIOLOGY
[79] Kose, Elif Odabas, In vitro activity of carvacrol in combination with meropenem against carbapenem‑resistant Klebsiella pneumoniae, 2021.0, FOLIA MICROBIOLOGICA
[80] Garcia-Salinas, Sara; Elizondo-Castillo, Hellen; Arruebo, Manuel; Mendoza, Gracia; Irusta, Silvia, Evaluation of the Antimicrobial Activity and Cytotoxicity of Different Components of Natural Origin Present in Essential Oils, 2018.0, MOLECULES
[81] Amato, D.N.; Amato, D.V.; Mavrodi, O.V.; Braasch, D.A.; Walley, S.E.; Douglas, J.R.; Mavrodi, D.V.; Patton, D.L., Destruction of Opportunistic Pathogens via Polymer Nanoparticle-Mediated Release of Plant-Based Antimicrobial Payloads, 2016.0, Advanced Healthcare Materials
[82] Montagu A, Joly-Guillou ML, Rossines E, Cayon J, Kempf M, Saulnier P., Stress Conditions Induced by Carvacrol and Cinnamaldehyde on Acinetobacter baumannii, 2016.0, Front Microbiol
[83] Cirino, Isis Caroline da Silva; de Santana, Caroline Ferreira; Bezerra, Maria Jose Ribeiro; Rocha, Igor Vasconcelos; Luz, Ana Carolina de Oliveira; Coutinho, Henrique Douglas Melo; de Figueiredo, Regina Celia Bressan Queiroz; Raposo, Antonio; Lho, Linda Heejung; Han, Heesup; Leal-Balbino, Tereza Cristina, Comparative transcriptomics analysis of multidrug-resistant Acinetobacter baumannii in response to treatment with the terpenic compounds thymol and carvacrol, 2023.0, BIOMEDICINE & PHARMACOTHERAPY
[84] Bassolé IH, Juliani HR., Essential Oils in Combination and Their Antimicrobial Properties , 2012.0, Molecules
[85] Kissels, W.; Wu, X.; Santos, R.R., Short communication: Interaction of the isomers carvacrol and thymol with the antibiotics doxycycline and tilmicosin: In vitro effects against pathogenic bacteria commonly found in the respiratory tract from calves, 2017.0, Journal of Dairy Science
[86] Woo SH, Park MK, Kang MC, Kim TK, Kim YJ, Shin DM, Ku SK, Park H, Lee H, Sung JM, Choi YS., Effects of Natural Extract Mixtures on the Quality Characteristics of Sausages during Refrigerated Storage, 2024.0, Food Sci Anim Resour
[87] Martins Alencar Souza, Victoria Vilaca; Almeida, Jaqueline Milagres; Barbosa, Lidiane Nunes; Cirone Silva, Nathalia Cristina, Citral, carvacrol, eugenol and thymol: antimicrobial activity and its application in food, 2022.0, JOURNAL OF ESSENTIAL OIL RESEARCH
[88] Moon, H.; Kim, N.H.; Kim, S.H.; Kim, Y.; Ryu, J.H.; Rhee, M.S., Teriyaki sauce with carvacrol or thymol effectively controls Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, and indigenous flora in marinated beef and marinade, 2017.0, Meat Science
[89] Boudechicha A, Aouf A, Ali H, Alsulami T, Badr AN, Ban Z, Farouk A., Effect of Microfluidization on the Volatiles and Antibacterial, Antifungal, and Cytotoxic Activities of Algerian Satureja hortensis L. Oil-Loaded Nanoemulsions: In Vitro and In Silico Study, 2024.0, ACS Omega
[90] Fernández-Babiano I, Navarro-Pérez ML, Pérez-Giraldo C, Fernández-Calderón MC., Antibacterial and Antibiofilm Activity of Carvacrol against Oral Pathogenic Bacteria, 2022.0, Metabolites
[91] Bonetti A, Tugnoli B, Rossi B, Giovagnoni G, Piva A, Grilli E., Nature-Identical Compounds and Organic Acids Reduce E. coli K88 Growth and Virulence Gene Expression In Vitro, 2020.0, Toxins (Basel)
[92] Pagan E, Merino N, Berdejo D, Campillo R, Gayan E, García-Gonzalo D, Pagan R., Adaptive evolution of Salmonella Typhimurium LT2 exposed to carvacrol lacks a uniform pattern, 2024.0, Appl Microbiol Biotechnol
[93] Chueca, Beatriz; Renzoni, Adriana; Berdejo, Daniel; Pagan, Rafael; Kelley, William L.; Garcia-Gonzalo, Diego, Whole-genome sequencing and genetic analysis reveals novel stress responses against individual constituents of essential oils in Escherichia coli, 2018.0, APPLIED AND ENVIRONMENTAL MICROBIOLOGY
[94] Chueca B, Berdejo D, Gomes-Neto NJ, Pagán R, García-Gonzalo D., Emergence of Hyper-Resistant Escherichia coli MG1655 Derivative Strains after Applying Sub-Inhibitory Doses of Individual Constituents of Essential Oils, 2016.0, Front Microbiol
[95] Kurek, Mia; Moundanga, Sylvie; Favier, Coralie; Galic, Kata; Debeaufort, Frederic, Antimicrobial efficiency of carvacrol vapour related to mass partition coefficient when incorporated in chitosan based films aimed for active packaging, 2013.0, FOOD CONTROL
[96] Šojić B, Ikonić P, Kocić-Tanackov S, Peulić T, Teslić N, Županjac M, Lončarević I, Zeković Z, Popović M, Vidaković S, Pavlić B., Antibacterial Activity of Selected Essential Oils against Foodborne Pathogens and Their Application in Fresh Turkey Sausages, 2023.0, Antibiotics (Basel)
[97] Cote, Heloise; Pichette, Andre; St-Gelais, Alexis; Legault, Jean, The Biological Activity of Monarda didyma L. Essential Oil and Its Effect as a Diet Supplement in Mice and Broiler Chicken, 2021.0, MOLECULES
[98] Cacciatore, Fabiola Ayres; Maders, Caroline; Alexandre, Bibiana; Pinilla, Cristian Mauricio Barreto; Brandelli, Adriano; Malheiros, Patricia da Silva, Carvacrol encapsulation into nanoparticles produced from chia and flaxseed mucilage: Characterization, stability and antimicrobial activity against Salmonella and Listeria monocytogenes, 2022.0, FOOD MICROBIOLOGY
[99] Falco, I; Verdegue, M.; Aznar, R.; Sanchez, G.; Randazzo, W., Sanitizing food contact surfaces by the use of essential oils, 2019.0, INNOVATIVE FOOD SCIENCE & EMERGING TECHNOLOGIES
[100] Arrieta, Marina P.; Peltzer, Mercedes A.; Lopez, Juan; del Carmen Garrigos, Maria; Valente, Artur J. M.; Jimenez, Alfonso, Functional properties of sodium and calcium caseinate antimicrobial active films containing carvacrol, 2013.0, JOURNAL OF FOOD ENGINEERING
[101] Hemmatian T, Seo KH, Yanilmaz M, Kim J., The Bacterial Control of Poly (Lactic Acid) Nanofibers Loaded with Plant-Derived Monoterpenoids via Emulsion Electrospinning, 2021.0, Polymers (Basel)
[102] Kosakowska O, Węglarz Z, Styczyńska S, Synowiec A, Gniewosz M, Bączek K., Activity of Common Thyme (Thymus vulgaris L.), Greek Oregano (Origanum vulgare L. ssp. hirtum), and Common Oregano (Origanum vulgare L. ssp. vulgare) Essential Oils against Selected Phytopathogens, 2024.0, Molecules
[103] Horváth, G.; Jámbor, N.; Somogyi-Végh, A.; Böszörményi, A.; Lemberkovics, É.; Héthelyi, É.; Kovácsc, K.; Kocsisc, B., Antimicrobial activity of essential oils: the possibilities of TLC–bioautography, 2010.0, Flavour and Fragrance Journal
[104] Hosseini S, Abdollahzadeh E, Ranaei V, Mahmoudzadeh M, Pilevar Z., Effect of Zataria multiflora Boiss. essential oil, NaCl, acid, time, and temperature on the growth of Listeria monocytogenes strains in broth and minced rainbow trout, 2021.0, Food Sci Nutr
[105] Rhayour, K; Bouchikhi, T; Tantaoui-Elaraki, A; Sendide, K; Remmal, A, The Mechanism of Bactericidal Action of Oregano and Clove Essential Oils and of Their Phenolic Major Components on Escherichia coli and Bacillus subtilis, 2003.0, JOURNAL OF ESSENTIAL OIL RESEARCH
[106] Pourhosseini, S.H.; Ahadi, H.; Aliahmadi, A.; Mirjalili, M.H., Chemical Composition and Antibacterial Activity of the Carvacrol-rich Essential Oils of Zataria multiflora Boiss. (Lamiaceae) from Southern Natural Habitats of Iran, 2020.0, Journal of Essential Oil-Bearing Plants
[107] Santos, Adriele R.; da Silva, Alex F.; Amaral, Viviane C. S.; Ribeiro, Alessandra B.; de Abreu Filho, Benicio A.; Mikcha, Jane M. G., Application of edible coating with starch and carvacrol in minimally processed pumpkin, 2016.0, JOURNAL OF FOOD SCIENCE AND TECHNOLOGY-MYSORE
[108] Kranzler, Markus; Frenzel, Elrike; Walser, Veronika; Hofmann, Thomas F.; Stark, Timo D.; Ehling-Schulz, Monika, Impact of Phytochemicals on Viability and Cereulide Toxin Synthesis in Bacillus cereus Revealed by a Novel High-Throughput Method, Coupling an AlamarBlue-Based Assay with UPLC-MS/MS, 2021.0, TOXINS
[109] da Silva Luz, I.; Gomes-Neto, N.J.; Magnani, M.; de Souza, E.L., Assessment of tolerance induction by Origanum vulgare L. essential oil or carvacrol in Pseudomonas aeruginosa cultivated in a meat-based broth and in a meat model, 2015.0, Food Science and Technology International
[110] Gaio, V.; Lima, C.A.; Oliveira, F.; França, Â.; Cerca, N., Carvacrol is highly disruptive against coagulase-negative staphylococci in in vitro biofilms, 2017.0, Future Microbiology
[111] Dimitrijevic, Mirjana; Grkovic, Nevena; Boskovic, Marija; Baltic, Milan Z.; Dojcinovic, Slobodan; Karabasil, Nedeljko; Vasilev, Dragan; Teodorovic, Vlado, Inhibition of Listeria monocytogenes growth on vacuum packaged rainbow trout (Oncorhynchus mykiss) with carvacrol and eugenol, 2019.0, JOURNAL OF FOOD SAFETY
[112] Klein, G.; Rueben, C.; Upmann, M., Antimicrobial Activity of Essential Oil Components Against Potential Food Spoilage Microorganisms, 2013.0, CURRENT MICROBIOLOGY
[113] Bianchi, Federica; Fornari, Fabio; Riboni, Nicolo; Spadini, Costanza; Cabassi, Clotilde Silvia; Iannarelli, Mattia; Carraro, Claudia; Mazzeo, Paolo Pio; Bacchi, Alessia; Orlandini, Serena; Furlanetto, Sandra; Careri, Maria, Development of novel cocrystal-based active food packaging by a Quality by Design approach, 2021.0, FOOD CHEMISTRY
[114] Periago, PM; Delgado, B; Fernández, PS; Palop, A, Use of Carvacrol and Cymene To Control Growth and Viability of Listeria monocytogenes Cells and Predictions of Survivors Using Frequency Distribution Functions, 2004.0, JOURNAL OF FOOD PROTECTION
[115] Ait-Ouazzou, A.; Espina, L.; Gelaw, T. K.; de Lamo-Castellvi, S.; Pagan, R.; Garcia-Gonzalo, D., New insights in mechanisms of bacterial inactivation by carvacrol, 2013.0, JOURNAL OF APPLIED MICROBIOLOGY
[116] Candelaria-Dueñas, S.; Serrano-Parrales, R.; Ávila-Romero, M.; Meraz-Martínez, S.; Orozco-Martínez, J.; Ávila-Acevédo, J.G.; García-Bores, A.M.; Céspedes-Acuña, C.L.; Peñalosa-Castro, I.; Hernández-Delgado, T., Evaluation of the Antimicrobial Activity of Some Components of the Essential Oils of Plants Used in the Traditional Medicine of the Tehuacán-Cuicatlán Valley, Puebla, México, 2021.0, Antibiotics
[117] Chiasson, F; Borsa, J; Ouattara, B; Lacroix, M, Radiosensitization of Escherichia coli and Salmonella Typhi in Ground Beef, 2004.0, JOURNAL OF FOOD PROTECTION
[118] Zodrow, K.R.; Schiffman, J.D.; Elimelech, M., Biodegradable Polymer (PLGA) Coatings Featuring Cinnamaldehyde and Carvacrol Mitigate Biofilm Formation, 2012.0, Langmuir
[119] Wang TH, Hsia SM, Wu CH, Ko SY, Chen MY, Shih YH, Shieh TM, Chuang LC, Wu CY., Evaluation of the Antibacterial Potential of Liquid and Vapor Phase Phenolic Essential Oil Compounds against Oral Microorganisms, 2016.0, PLoS One
[120] Raei, P.; Pourlak, T.; Memar, M.Y.; Alizadeh, N.; Aghamali, M.; Zeinalzadeh, E.; Asgharzadeh, M.; Kafil, H.S., Thymol and carvacrol strongly inhibit biofilm formation and growth of carbapenemase-producing Gram negative bacilli, 2017.0, Cellular and Molecular Biology
[121] Zheng, Ling; Bae, Young-Min; Jung, Kyu-Seok; Heu, Sunggi; Lee, Sun-Young, Antimicrobial activity of natural antimicrobial substances against spoilage bacteria isolated from fresh produce, 2013.0, FOOD CONTROL
[122] Garcia-Garcia, Rebeca; Lopez-Malo, Aurelio; Palou, Enrique, Bactericidal Action of Binary and Ternary Mixtures of Carvacrol, Thymol, and Eugenol against Listeria innocua, 2011.0, JOURNAL OF FOOD SCIENCE
[123] Popa M, Măruțescu L, Oprea E, Bleotu C, Kamerzan C, Chifiriuc MC, Grădișteanu Pircalabioru G., In Vitro Evaluation of the Antimicrobial and Immunomodulatory Activity of Culinary Herb Essential Oils as Potential Perioceutics, 2020.0, Antibiotics (Basel)
[124] Baskaran, S. Ananda; Kazmer, G. W.; Hinckley, L.; Andrew, S. M.; Venkitanarayanan, K., Antibacterial effect of plant-derived antimicrobials on major bacterial mastitis pathogens in vitro, 2009.0, JOURNAL OF DAIRY SCIENCE
[125] de Sousa Silveira, Zildene; Macedo, Nair Silva; Sampaio dos Santos, Joycy Francely; de Freitas, Thiago Sampaio; dos Santos Barbosa, Cristina Rodrigues; de Sousa Junior, Darcio Luiz; Muniz, Debora Feitosa; Castro de Oliveira, Ligia Claudia; Siqueira Junior, Jose Pinto; Bezerra da Cunha, Francisco Assis; Melo Coutinho, Henrique Douglas; Balbino, Valdir Queiroz; Martins, Natalia, Evaluation of the Antibacterial Activity and Efflux Pump Reversal of Thymol and Carvacrol against Staphylococcus aureus and Their Toxicity in Drosophila melanogaster, 2020.0, MOLECULES
[126] Veldhuizen, Edwin J. A.; Creutzberg, T. Olaf; Burt, Sara A.; Haagsman, Henk P., Low Temperature and Binding to Food Components Inhibit the Antibacterial Activity of Carvacrol against Listeria monocytogenes in Steak Tartare, 2007.0, JOURNAL OF FOOD PROTECTION
[127] Alves, Fernanda C. B.; Barbosa, Lidiane N.; Andrade, Bruna F. M. T.; Albano, Mariana; Furtado, Fabiana Barcelos; Marques Pereira, Ana Flavia; Rall, Vera L. M.; Fernandes Junior, Ary, Short communication: Inhibitory activities of the lantibiotic nisin combined with phenolic compounds against Staphylococcus aureus and Listeria monocytogenes in cow milk, 2016.0, JOURNAL OF DAIRY SCIENCE
[128] Mizielinska, Malgorzata; Nawrotek, Pawel; Stachurska, Xymena; Ordon, Magdalena; Bartkowiak, Artur, Packaging Covered with Antiviral and Antibacterial Coatings Based on ZnO Nanoparticles Supplemented with Geraniol and Carvacrol, 2021.0, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
[129] Rivas, Lucia; McDonnell, Mary J.; Burgess, Catherine M.; O'Brien, Martin; Navarro-Villa, Alberto; Fanning, Seamus; Duffy, Geraldine, Inhibition of verocytotoxigenic Escherichia coli in model broth and rumen systems by carvacrol and thymol, 2010.0, INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY
[130] Niza, Enrique; Bozik, Matej; Bravo, Ivan; Clemente-Casares, Pilar; Lara-Sanchez, Agustin; Juan, Alberto; Kloucek, Pavel; Alonso-Moreno, Carlos, PEI-coated PLA nanoparticles to enhance the antimicrobial activity of carvacrol, 2020.0, FOOD CHEMISTRY
[131] Pierozan MB, Oliveira Filho JG, Cappato LP, Costa AC, Egea MB., Essential Oils Against Spoilage in Fish and Seafood: Impact on Product Quality and Future Challenges, 2024.0, Foods
[132] Zhu, L.; Olsen, C.; McHugh, T.; Friedman, M.; Jaroni, D.; Ravishankar, S., Apple, Carrot, and Hibiscus Edible Films Containing the Plant Antimicrobials Carvacrol and Cinnamaldehyde Inactivate Salmonella Newport on Organic Leafy Greens in Sealed Plastic Bags, 2014.0, Journal of Food Science
[133] Fernandez-Pan, I.; Mate, J. I.; Gardrat, C.; Coma, V., Effect of chitosan molecular weight on the antimicrobial activity and release rate of carvacrol-enriched films, 2015.0, FOOD HYDROCOLLOIDS
[134] Otero-Tuarez, Victor; Carrion-Granda, Ximena; Fernandez-Pan, Idoya; Fernandez, Teresa; Mate, Juan I., Combined effect of antimicrobial edible coatings with reduction of initial microbial load on the shelf-life of fresh hake (Merluccius merluccius) medallions, 2019.0, INTERNATIONAL JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
[135] Košćak L, Lamovšek J, Đermić E, Godena S., The Antibacterial Effect of Selected Essential Oils and Their Bioactive Constituents on Pseudomonas savastanoi pv. savastanoi: Phytotoxic Properties and Potential for Future Olive Disease Control, 2023.0, Microorganisms
[136] Sharifi-Rad, Mehdi; Varoni, Elena Maria; Iriti, Marcello; Martorell, Miquel; Setzer, William N.; del Mar Contreras, Maria; Salehi, Bahare; Soltani-Nejad, Azam; Rajabi, Sadegh; Tajbakhsh, Mercedeh; Sharifi-Rad, Javad, Carvacrol and human health: A comprehensive review, 2018.0, PHYTOTHERAPY RESEARCH
[137] Wang J, Qin T, Chen K, Pan L, Xie J, Xi B., Antimicrobial and Antivirulence Activities of Carvacrol against Pathogenic Aeromonas hydrophila, 2022.0, Microorganisms
[138] Kasthuri T, Swetha TK, Bhaskar JP, Pandian SK., Rapid-killing efficacy substantiates the antiseptic property of the synergistic combination of carvacrol and nerol against nosocomial pathogens, 2022.0, Arch Microbiol
[139] Erguden, B., Phenol group of terpenoids is crucial for antibacterial activity upon ion leakage, 2021.0, LETTERS IN APPLIED MICROBIOLOGY
[140] Belda-Galbis, Clara Miracle; Leufven, Anders; Martinez, Antonio; Rodrigo, Dolores, Predictive microbiology quantification of the antimicrobial effect of carvacrol, 2014.0, JOURNAL OF FOOD ENGINEERING
[141] Su F, Yang G, Hu D, Ruan C, Wang J, Zhang Y, Zhu Q., Chemical Composition, Antibacterial and Antioxidant Activities of Essential Oil from Centipeda minima, 2023.0, Molecules
[142] Ultee, A; Kets, EPW; Alberda, M; Hoekstra, FA; Smid, EJ, Adaptation of the food-borne pathogen Bacillus cereus to carvacrol, 2000.0, ARCHIVES OF MICROBIOLOGY
[143] Yamaguchi, Takayoshi, Antibacterial effect of the combination of terpenoids, 2022.0, ARCHIVES OF MICROBIOLOGY
[144] Ultee, A; Slump, RA; Steging, G; Smid, EJ, Antimicrobial Activity of Carvacrol toward Bacillus cereus on Rice, 2000.0, JOURNAL OF FOOD PROTECTION
[145] Esteban, Maria-Dolores; Aznar, Arantxa; Fernandez, Pablo S.; Palop, Alfredo, Combined effect of nisin, carvacrol and a previous thermal treatment on the growth of Salmonella enteritidis and Salmonella senftenberg, 2013.0, FOOD SCIENCE AND TECHNOLOGY INTERNATIONAL
[146] Touil, Hidaya F. Z.; Boucherit, Kebir; Boucherit-Otmani, Zahia; Kohder, Ghalia; Madkour, Mohamed; Soliman, Sameh S. M., Optimum Inhibition of Amphotericin-B-Resistant Candida albicans Strain in Single- and Mixed-Species Biofilms by Candida and Non-Candida Terpenoids, 2020.0, BIOMOLECULES
[147] Szczepaniak, S.; Polanska, M.; Van Assche, A.; Moloney, R.; Willems, K. A., The synergism of natural compounds in the pursuit of safe and healthier food, 2011.0, JOURNAL OF INDUSTRIAL MICROBIOLOGY & BIOTECHNOLOGY
[148] Jugreet, B.S.; Mahomoodally, M.F., Essential oils from 9 exotic and endemic medicinal plants from Mauritius shows in vitro antibacterial and antibiotic potentiating activities, 2020.0, South African Journal of Botany
[149] Gutiérrez-Fernández, J.; García-Armesto, M.R.; Álvarez-Alonso, R.; del Valle, P.; Arriaga, D.; Rúa, J., Antimicrobial activity of binary combinations of natural and synthetic phenolic antioxidants against Enterococcus faecalis, 2013.0, Journal of Dairy Science
[150] Sorca BV, Kaya DA, Kaya MGA, Enachescu M, Ghetu DM, Enache LB, Boerasu I, Coman AE, Rusu LC, Constantinescu R, Titorencu I., Bone Fillers with Balance Between Biocompatibility and Antimicrobial Properties, 2025.0, Biomimetics (Basel)
[151] Silva-Angulo, A. B.; Zanini, S. F.; Rosenthal, A.; Rodrigo, D.; Klein, G.; Martinez, A., Combined effect of carvacrol and citral on the growth of Listeria monocytogenes and Listeria innocua and on the occurrence of damaged cells, 2015.0, FOOD CONTROL
[152] Imtara H, Elamine Y, Lyoussi B., Honey Antibacterial Effect Boosting Using Origanum vulgare L. Essential Oil, 2018.0, Evid Based Complement Alternat Med
[153] Kim, M.S.; Kim, H.-R.; Kim, H.; Choi, S.-K.; Kim, C.-H.; Hwang, J.-K.; Park, S.-H., Expansion of antibacterial spectrum of xanthorrhizol against Gram-negatives in combination with PMBN and food-grade antimicrobials, 2019.0, Journal of Microbiology
[154] Olasupo, N.A.; Fitzgerald, D.J.; Narbad, A.; Gasson, M.J., Inhibition of Bacillus subtilis and Listeria innocua by Nisin in Combination with Some Naturally Occurring Organic Compounds, 2004.0, Journal of Food Protection
[155] Zanini, S. F.; Silva-Angulo, A. B.; Rosenthal, A.; Rodrigo, D.; Martinez, A., Effect of citral and carvacrol on the susceptibility of Listeria monocytogenes and Listeria innocua to antibiotics, 2014.0, LETTERS IN APPLIED MICROBIOLOGY
[156] Kavoosi, Gholamreza; Dadfar, Seyed Mohammad Mahdi; Purfard, Amin Mohammadi; Mehrabi, Reza, ANTIOXIDANT AND ANTIBACTERIAL PROPERTIES OF GELATIN FILMS INCORPORATED WITH CARVACROL, 2014.0, JOURNAL OF FOOD SAFETY
[157] Gaglio, Raimondo; Botta, Luigi; Garofalo, Giuliana; Miceli, Alessandro; Settanni, Luca; Lopresti, Francesco, Carvacrol activated biopolymeric foam: An effective packaging system to control the development of spoilage and pathogenic bacteria on sliced pumpkin and melon, 2021.0, FOOD PACKAGING AND SHELF LIFE
[158] GholipourKanani, H.; Buller, N.; Lymbery, A., In vitro antibacterial activity of four nano‐encapsulated herbal essential oils against three bacterial fish pathogens, 2019.0, Aquaculture Research
[159] Maccelli, Alessandro; Vitanza, Luca; Imbriano, Anna; Fraschetti, Caterina; Filippi, Antonello; Goldoni, Paola; Maurizi, Linda; Ammendolia, Maria Grazia; Crestoni, Maria Elisa; Fornarini, Simonetta; Menghini, Luigi; Carafa, Maria; Marianecci, Carlotta; Longhi, Catia; Rinaldi, Federica, Satureja montana L. Essential Oils: Chemical Profiles/Phytochemical Screening, Antimicrobial Activity and O/W NanoEmulsion Formulations, 2020.0, PHARMACEUTICS
[160] Arana-Sanchez, A.; Estarron-Espinosa, M.; Obledo-Vazquez, E. N.; Padilla-Camberos, E.; Silva-Vazquez, R.; Lugo-Cervantes, E., Antimicrobial and antioxidant activities of Mexican oregano essential oils (Lippia graveolens H. B. K.) with different composition when microencapsulated in b-cyclodextrin, 2010.0, LETTERS IN APPLIED MICROBIOLOGY
[161] Santiesteban-Lopez, A.; Palou, E.; Lopez-Malo, A., Susceptibility of food-borne bacteria to binary combinations of antimicrobials at selected aw and pH, 2007.0, JOURNAL OF APPLIED MICROBIOLOGY
[162] Saghari V, Jalali H, Shariatifar N, Ziaolhagh S., Evaluation of whey protein coating containing free and Pickering emulsion forms of Trachyspermum copticum L. essential oil on quality of refrigerated beef, 2024.0, Food Sci Nutr
[163] Omran Z, Bader A, Porta A, Vandamme T, Anton N, Alehaideb Z, El-Said H, Faidah H, Essa A, Vassallo A, Halwani M., Evaluation of Antimicrobial Activity of Triphala Constituents and Nanoformulation, 2020.0, Evid Based Complement Alternat Med
[164] Sotelo-Boyas, M.; Correa-Pacheco, Z.; Bautista-Batnos, S.; Gomez y Gomez, Y., Release study and inhibitory activity of thyme essential oil-loaded chitosan nanoparticles and nanocapsules against foodborne bacteria, 2017.0, INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
[165] Santos, Emerson H.; Kamimura, Juliane A.; Hill, Laura E.; Gomes, Carmen L., Characterization of carvacrol beta-cyclodextrin inclusion complexes as delivery systems for antibacterial and antioxidant applications, 2015.0, LWT-FOOD SCIENCE AND TECHNOLOGY
[166] Safakas K, Giotopoulou I, Giannakopoulou A, Katerinopoulou K, Lainioti GC, Stamatis H, Barkoula NM, Ladavos A., Designing Antioxidant and Antimicrobial Polyethylene Films with Bioactive Compounds/Clay Nanohybrids for Potential Packaging Applications, 2023.0, Molecules
[167] Jayari A, Donsì F, Ferrari G, Maaroufi A., Nanoencapsulation of Thyme Essential Oils: Formulation, Characterization, Storage Stability, and Biological Activity, 2022.0, Foods
[168] Firmino JP, Fernández-Alacid L, Vallejos-Vidal E, Salomón R, Sanahuja I, Tort L, Ibarz A, Reyes-López FE, Gisbert E., Carvacrol, Thymol, and Garlic Essential Oil Promote Skin Innate Immunity in Gilthead Seabream (Sparus aurata) Through the Multifactorial Modulation of the Secretory Pathway and Enhancement of Mucus Protective Capacity, 2021.0, Front Immunol
[169] Ulloa, Pablo A.; Guarda, Abel; Valenzuela, Ximena; Rubilar, Javiera F.; Galotto, Maria J., Modeling the release of antimicrobial agents (thymol and carvacrol) from two different encapsulation materials, 2018.0, FOOD SCIENCE AND BIOTECHNOLOGY
[170] Bartošová L, Sedlaříková J, Peer P, Janalíková M, Pleva P., Antibacterial and Antifouling Efficiency of Essential Oils-Loaded Electrospun Polyvinylidene Difluoride Membranes, 2022.0, Int J Mol Sci
[171] Nostro, A.; Scaffaro, R.; Botta, L.; Filocamo, A.; Marino, A.; Bisignano, G., Effect of temperature on the release of carvacrol and cinnamaldehyde incorporated into polymeric systems to control growth and biofilms of Escherichia coli and Staphylococcus aureus, 2015.0, Biofouling
[172] Du, W.-X.; Avena-Bustillos, R.J.; Woods, R.; Breksa, A.P.; McHugh, T.H.; Friedman, M.; LEVIN, C.E.; Mandrell, R., Sensory Evaluation of Baked Chicken Wrapped with Antimicrobial Apple and Tomato Edible Films Formulated with Cinnamaldehyde and Carvacrol, 2012.0, Journal of Agricultural and Food Chemistry
[173] de Castro, D.O.; Tabary, N.; Martel, B.; Gandini, A.; Belgacem, N.; Bras, J., Effect of different carboxylic acids in cyclodextrin functionalization of cellulose nanocrystals for prolonged release of carvacrol, 2016.0, Materials Science and Engineering C
[174] Ramos, Marina; Jimenez, Alfonso; Peltzer, Mercedes; Garrigos, Maria C., Characterization and antimicrobial activity studies of polypropylene films with carvacrol and thymol for active packaging, 2012.0, JOURNAL OF FOOD ENGINEERING
[175] Lombardi, Andrea; Fochetti, Andrea; Vignolini, Pamela; Campo, Margherita; Durazzo, Alessandra; Lucarini, Massimo; Puglia, Debora; Luzi, Francesca; Papalini, Marco; Renzi, Monia; Cavallo, Andrea; Bernini, Roberta, Natural Active Ingredients for Poly (Lactic Acid)-Based Materials: State of the Art and Perspectives, 2022.0, ANTIOXIDANTS
[176] Laroque, Denise A.; de Jong, Naomi R.; Muller, Leidiani; Paganini, Camila C.; de Araujo, Pedro H. H.; de Araga, Glaucia M. F.; Carciofi, Bruno A. M., Carvacrol release kinetics from cellulose acetate films and its antibacterial effect on the shelf life of cooked ham, 2023.0, JOURNAL OF FOOD ENGINEERING
[177] Tampau, Alina; Gonzalez-Martinez, Chelo; Chiralt, Amparo, Release kinetics and antimicrobial properties of carvacrol encapsulated in electrospun poly-(ε-caprolactone) nanofibres. Application in starch multilayer films, 2018.0, FOOD HYDROCOLLOIDS
[178] Requena, Raquel; Vargas, Maria; Chiralt, Amparo, Obtaining antimicrobial bilayer starch and polyester-blend films with carvacrol, 2018.0, FOOD HYDROCOLLOIDS
[179] Laroque, Denise Adamoli; Falcao de Aragao, Glaucia Maria; Hermes de Araujo, Pedro Henrique; Mattar Carciofi, Bruno Augusto, Active cellulose acetate-carvacrol films: Antibacterial, physical and thermal properties, 2021.0, PACKAGING TECHNOLOGY AND SCIENCE
[180] Issa A, Ibrahim SA, Tahergorabi R., Impact of Sweet Potato Starch-Based Nanocomposite Films Activated With Thyme Essential Oil on the Shelf-Life of Baby Spinach Leaves, 2017.0, Foods
[181] Oussalah, M.; Caillet, S.; Salmiéri, S.; Saucier, L.; Lacroix, M., Antimicrobial and Antioxidant Effects of Milk Protein-Based Film Containing Essential Oils for the Preservation of Whole Beef Muscle, 2004.0, Journal of Agricultural and Food Chemistry
[182] Goktepe, Sevi; Ocak, Bugra; Ozdestan-Ocak, Ozgul, Physico‑chemical, Sensory, and Antioxidant Characteristics of Olive Paste Enriched with Microencapsulated Thyme Essential Oil, 2021.0, FOOD AND BIOPROCESS TECHNOLOGY
[183] Nouri Ala, M.A.; Shahbazi, Y., The effects of novel bioactive carboxymethyl cellulose coatings on food-borne pathogenic bacteria and shelf life extension of fresh and sauced chicken breast fillets, 2019.0, LWT
[184] Lim, G.O.; Hong, Y.H.; Song, K.B., Application of Gelidium corneum Edible Films Containing Carvacrol for Ham Packages, 2010.0, Journal of Food Science
[185] Wroblewska, Agnieszka; Fajdek-Bieda, Anna; Markowska-Szczupak, Agata; Radkowska, Monika, Preliminary Microbiological Tests of S-Carvone and Geraniol and Selected Derivatives of These Compounds That May Be Formed in the Processes of Isomerization and Oxidation, 2022.0, MOLECULES
[186] Kovačević Z, Tomanić D, Čabarkapa I, Šarić L, Stanojević J, Bijelić K, Galić I, Ružić Z, Erdeljan M, Kladar N., Chemical Composition, Antimicrobial Activity, and Withdrawal Period of Essential Oil-Based Pharmaceutical Formulation in Bovine Mastitis Treatment, 2022.0, Int J Environ Res Public Health
[187] Rozenblit, Boris; Tenenbaum, Guy; Shagan, Alona; Salkmon, Enav Corem; Shabtay-Orbach, Ayelet; Mizrahi, Boaz, A new volatile antimicrobial agent-releasing patch for preserving fresh foods, 2018.0, FOOD PACKAGING AND SHELF LIFE
[188] Patel, J.; Keelara, S.; Green, J., Inactivation of Escherichia coli O157:H7 and Salmonella on Fresh Herbs by Plant Essential Oils, 2018.0, Foodborne Pathogens and Disease
[189] Kačániová M, Garzoli S, Ben Hsouna A, Bianchi A, Kluz MI, Elizondo-Luevano JH, Ban Z, Ben Saad R, Mnif W, Haščík P., The Potential of Thymus serpyllum Essential Oil as an Antibacterial Agent against Pseudomonas aeruginosa in the Preservation of Sous Vide Red Deer Meat, 2024.0, Foods
[190] Landry, Kyle S.; Chang, Yuhua; McClements, David Julian; McLandsborough, Lynne, Effectiveness of a novel spontaneous carvacrol nanoemulsion against Salmonella enterica Enteritidis and Escherichia coli O157:H7 on contaminated mung bean and alfalfa seeds, 2014.0, INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY
[191] Zantar, Said; Yedri, Faiza; Mrabet, Rachid; Laglaoui, Amin; Bakkali, Mohammed; Zerrouk, Mounir Hassani, Effect of Thymus vulgaris and Origanum compactum essential oils on the shelf life of fresh goat cheese, 2014.0, JOURNAL OF ESSENTIAL OIL RESEARCH
[192] Liu, S.; Song, M.; Yun, W.; Lee, J.; Lee, C.; Kwak, W.; Han, N.; Kim, H.; Cho, J., Effects of oral administration of different dosages of carvacrol essential oils on intestinal barrier function in broilers, 2018.0, Journal of Animal Physiology and Animal Nutrition
[193] Zhao BC, Wang TH, Chen J, Qiu BH, Xu YR, Li JL., Essential oils improve nursery pigs' performance and appetite via modulation of intestinal health and microbiota, 2023.0, Anim Nutr
[194] Reis, J.H.; Gebert, R.R.; Barreta, M.; Dellaméa Baldissera, M.D.; Dos Santos, I.D.; Wagner, R.; Campigotto, G.; Jaguezeski, A.M.; Gris, A.; de Lima, J.L.F.; Mendes, R.E.; Fracasso, M.; Boiago, M.M.; Stefani, L.M.; Dos-Santos, D.S.; Robazza, W.S.; da Silva, A.S., Effects of phytogenic feed additive based on thymol, carvacrol and cinnamic aldehyde on body weight, blood parameters and environmental bacteria in broilers chickens, 2018.0, Microbial Pathogenesis
[195] Hoa TTT, Fagnon MS, Thy DTM, Chabrillat T, Trung NB, Kerros S., Growth Performance and Disease Resistance against Vibrio parahaemolyticus of Whiteleg Shrimp (Litopenaeus vannamei) Fed Essential Oil Blend (Phyto AquaBiotic), 2023.0, Animals (Basel)
[196] Poudel P, Froehlich K, Casper DP, St-Pierre B., Feeding Essential Oils to Neonatal Holstein Dairy Calves Results in Increased Ruminal Prevotellaceae Abundance and Propionate Concentrations, 2019.0, Microorganisms
[197] Oliveira GDS, McManus C, de Araújo MV, de Sousa DER, de Macêdo IL, Castro MB, Santos VMD., Sanitizing Hatching Eggs with Essential Oils: Avian and Microbiological Safety, 2023.0, Microorganisms
[198] Betancourt-López, L.; Rodríguez-Villamizar, F.; Phandanouvong, V.; Nieto, C.; Hume, M.; Nisbet, D.; Afanador-Tellez, G.; van Kley, A.M.; Nalian, A., Effect of Origanum chemotypes on broiler intestinal bacteria, 2014.0, Poultry Science
[199] Chaichi, M.; Mohammadi, A.; Badii, F.; Hashemi, M., Triple synergistic essential oils prevent pathogenic and spoilage bacteria growth in the refrigerated chicken breast meat, 2021.0, Biocatalysis and Agricultural Biotechnology
[200] Napiórkowska A, Khaneghah AM, Kurek MA., Essential Oil Nanoemulsions—A New Strategy to Extend the Shelf Life of Smoothies, 2024.0, Foods