Unravelling the Complex Antimicrobial Interactions of Essential Oils — The Case of Thymus vulgaris (Thyme)
Abstract
:1. Introduction
2. Results and Discussion
2.1. Essential Oil Composition
2.2. Minimum Inhibitory Concentrations (MIC)
Compounds | RRI | % of oil |
---|---|---|
α-Pinene | 1016 | 0.63 |
α-Thujene | 1019 | 0.50 |
Camphene | 1057 | 0.61 |
β-Pinene | 1104 | 0.17 |
Myrcene | 1159 | 1.17 |
α-Terpinene | 1174 | 1.01 |
Limonene | 1194 | 0.35 |
1,8 Cineole | 1202 | 0.24 |
β-Phellandrene | 1203 | 0.13 |
γ-Terpinene | 1242 | 6.39 |
p-Cymene | 1270 | 15.44 |
Camphor | 1521 | 0.39 |
Linalool | 1541 | 4.22 |
β-Caryophyllene | 1596 | 1.31 |
Terpinen-4-ol | 1602 | 0.93 |
Thymol methyl ether | 1607 | 0.51 |
Boroneol | 1702 | 1.76 |
α-Terpineol | 1707 | 0.32 |
δ-Cadinene | 1763 | 0.09 |
Isothymol | 2171 | 0.12 |
Thymol | 2225 | 60.18 |
Carvacrol | 2228 | 2.88 |
Total: | 99.35 |
Pathogen | Minimum Inhibitory Concentrations (mg mL−1) | ||||||||
---|---|---|---|---|---|---|---|---|---|
TvEO | Thymol | Carvacrol | Linalool | p-Cymene | Borneol | α-Terpinene | γ-Terpinene | Controls * | |
Escherichia coli ATCC8739 | 0.500 | 1 | 1 | 4 | >8 | >8 | 8 | >8 | 0.0005 |
Morexella cattarhalis ATCC23246 | 0.500 | 1 | 1 | 2 | >8 | 8 | 8 | >8 | 0.001 |
Staphylococcus aureus ATCC126000 | 0.500 | 1 | 0.500 | 2 | >8 | 8 | 4 | 8 | 0.0005 |
Enterococcus faecalis ATCC29212 | 0.125 | 0.500 | 0.500 | 1 | >8 | 4 | 8 | >8 | 0.001 |
Bacillus cereusATCC11778 | 0.125 | 0.500 | 0.250 | 2 | >8 | 8 | 4 | 8 | 0.0002 |
Candida albicans ATCC10231 | 0.062 | 0.125 | 0.125 | 2 | >8 | 1 | 1 | 8 | 0.001 |
Candida tropicalisATCC201380 | 0.062 | 0.125 | 0.125 | 0.250 | >8 | 1 | 0.250 | 4 | 0.001 |
EO compoundsmg mL−1 | E. coli | INT | M. cattarhalis | INT | S. aureus | INT | E. faecalis | INT | B. cereus | INT | C. albicans | INT | C. tropicals | INT | ||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
THY + CARV | FICA | 0.500 | ADD | 0.500 | ADD | 1.000 | IND | 1.000 | IND | 1.000 | IND | 0.500 | ADD | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.500 | 0.500 | 2.000 | 1.000 | 2.000 | 0.500 | 0.500 | |||||||||||||||||||||||||||||||||||||
∑FIC | 1.000 | 1.000 | 3.000 | 2.000 | 3.000 | 1.000 | 1.000 | |||||||||||||||||||||||||||||||||||||
THY + LIN | FICA | 0.500 | ADD | 1.000 | IND | 0.500 | ADD | 0.500 | ADD | 2.000 | IND | 0.500 | ADD | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.250 | 0.500 | 0.250 | 0.250 | 0.500 | 0.031 | 0.250 | |||||||||||||||||||||||||||||||||||||
∑FIC | 0.750 | 1.500 | 0.750 | 0.750 | 2.500 | 0.531 | 0.750 | |||||||||||||||||||||||||||||||||||||
THY + CYM | FICA | 1.000 | IND | 0.250 | SYN | 0.250 | SYN | 1.000 | IND | 1.000 | IND | 0.500 | SYN | 0.500 | SYN | |||||||||||||||||||||||||||||
FICB | 0.063 | 0.031 | 0.031 | 0.031 | 0.031 | 0.004 | 0.004 | |||||||||||||||||||||||||||||||||||||
∑FIC | 1.063 | 0.281 | 0.281 | 1.031 | 1.031 | 0.504 | 0.504 | |||||||||||||||||||||||||||||||||||||
THY + BOR | FICA | 1.000 | IND | 4.000 | ANT | 0.500 | ADD | 2.000 | IND | 0.250 | SYN | 0.500 | ADD | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.063 | 1.000 | 0.062 | 0.250 | 0.016 | 0.063 | 0.250 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 1.063 | 5.000 | 0.562 | 2.250 | 0.261 | 0.563 | 0.750 | |||||||||||||||||||||||||||||||||||||
THY + α-TER | FICA | 1.000 | IND | 0.500 | ADD | 1.000 | IND | 1.000 | IND | 0.500 | ADD | 2.000 | IND | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.120 | 0.063 | 0.250 | 0.063 | 0.063 | 0.250 | 0.250 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 1.125 | 0.563 | 1.250 | 1.063 | 0.563 | 2.250 | 0.750 | |||||||||||||||||||||||||||||||||||||
THY + γ -TER | FICA | 1.000 | IND | 1.000 | IND | 1.000 | IND | 2.000 | IND | 2.000 | IND | 1.000 | IND | 1.000 | IND | |||||||||||||||||||||||||||||
FICB | 0.063 | 0.063 | 0.125 | 0.063 | 0.125 | 0.015 | 0.031 | |||||||||||||||||||||||||||||||||||||
∑FIC | 1.063 | 1.063 | 1.125 | 2.063 | 2.125 | 1.015 | 1.031 | |||||||||||||||||||||||||||||||||||||
CARV + LIN | FICA | 0.500 | ADD | 0.500 | ADD | 0.500 | ADD | 1.000 | IND | 0.250 | SYN | 0.500 | ADD | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.250 | 0.250 | 0.125 | 0.500 | 0.030 | 0.031 | 0.250 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 0.750 | 0.750 | 0.625 | 1.500 | 0.281 | 0.531 | 0.750 | |||||||||||||||||||||||||||||||||||||
CARV + CYM | FICA | 0.125 | SYN | 0.125 | SYN | 0.500 | SYN | 0.500 | SYN | 0.250 | SYN | 1.000 | IND | 1.000 | IND | |||||||||||||||||||||||||||||
FICB | 0.032 | 0.008 | 0.008 | 0.008 | 0.008 | 0.008 | 0.008 | |||||||||||||||||||||||||||||||||||||
∑FIC | 0.157 | 0.133 | 0.508 | 0.508 | 0.258 | 1.008 | 1.008 | |||||||||||||||||||||||||||||||||||||
CARV + BOR | FICA | 2.000 | IND | 0.500 | ADD | 0.250 | SYN | 0.500 | ADD | 0.500 | ADD | 0.500 | ADD | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.125 | 0.125 | 0.015 | 0.125 | 0.016 | 0.063 | 0.250 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 2.125 | 0.625 | 0.265 | 0.625 | 0.516 | 0.563 | 0.750 | |||||||||||||||||||||||||||||||||||||
α-TER + CARV | FICA | 0.500 | ADD | 0.500 | ADD | 0.250 | SYN | 1.000 | IND | 0.250 | SYN | 0.250 | SYN | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.625 | 0.063 | 0.062 | 0.063 | 0.250 | 0.063 | 0.250 | |||||||||||||||||||||||||||||||||||||
FIC | 0.562 | 0.563 | 0.312 | 1.063 | 0.500 | 0.313 | 0.750 | |||||||||||||||||||||||||||||||||||||
CARV + γ -TER | FICA | 0.500 | ADD | 0.500 | ADD | 0.250 | ANT | 1.000 | IND | 0.500 | ADD | 0.250 | SYN | 0.500 | ADD | |||||||||||||||||||||||||||||
FICB | 0.063 | 0.031 | 4.000 | 0.031 | 0.030 | 0.015 | 0.015 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 0.563 | 0.531 | 4.250 | 1.031 | 0.530 | 0.265 | 0.515 | |||||||||||||||||||||||||||||||||||||
LIN + CYM | FICA | 2.000 | IND | 0.250 | SYN | 1.000 | IND | 0.500 | ADD | 1.000 | IND | 1.000 | IND | 0.125 | SYN | |||||||||||||||||||||||||||||
FICB | 0.250 | 0.062 | 0.125 | 0.063 | 0.125 | 0.125 | 0.016 | |||||||||||||||||||||||||||||||||||||
FIC | 2.250 | 0.312 | 1.125 | 0.563 | 1.125 | 1.125 | 0.141 | |||||||||||||||||||||||||||||||||||||
LIN + BOR | FICA | 0.500 | ADD | O.500 | ADD | 0.250 | SYN | 0.500 | ADD | 0.250 | SYN | 0.250 | ADD | 1.000 | IND | |||||||||||||||||||||||||||||
FICB | 0.125 | 0.250 | 0.062 | 0.125 | 0.063 | 0.500 | 1.000 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 0.625 | 0.750 | 0.312 | 0.625 | 0.312 | 0.750 | 2.000 | |||||||||||||||||||||||||||||||||||||
LIN +α-TER | FICA | 0.250 | SYN | 0.500 | ADD | 1.000 | IND | 0.250 | SYN | 0.500 | ADD | 0.500 | IND | 0.250 | SYN | |||||||||||||||||||||||||||||
FICB | 0.063 | 0.125 | 0.500 | 0.031 | 0.250 | 1.000 | 0.250 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 0.312 | 0.625 | 1.500 | 0.281 | 0.750 | 1.500 | 0.500 | |||||||||||||||||||||||||||||||||||||
LIN + γ -TER | FICA | 1.000 | IND | 0.500 | ADD | 1.000 | IND | 2.000 | IND | 0.500 | ADD | 0.500 | ADD | 1.000 | IND | |||||||||||||||||||||||||||||
FICB | 0.120 | 0.063 | 0.250 | 0.125 | 0.125 | 0.125 | 0.063 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 1.120 | 0.563 | 1.250 | 2.125 | 0.625 | 0.625 | 1.063 | |||||||||||||||||||||||||||||||||||||
CYM + BOR | FICA | 0.500 | ADD | 0.063 | SYN | 0.250 | SYN | 0.250 | IND | 0.250 | ADD | 0.125 | IND | 1.000 | IND | |||||||||||||||||||||||||||||
FICB | 0.500 | 0.125 | 0.125 | 1.000 | 0.500 | 2.000 | 0.015 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 1.00 | 0.188 | 0.375 | 1.250 | 0.750 | 2.125 | 1.015 | |||||||||||||||||||||||||||||||||||||
CYM + α-TER | FICA | 0.500 | IND | 0.250 | ADD | 0.500 | IND | 0.250 | ADD | 0.250 | IND | 0.125 | IND | 1.000 | IND | |||||||||||||||||||||||||||||
FICB | 1.000 | 0.500 | 2.000 | 0.500 | 1.000 | 2.000 | 0.015 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 1.500 | 0.750 | 2.500 | 0.750 | 1.250 | 2.125 | 1.015 | |||||||||||||||||||||||||||||||||||||
CYM + γ -TER | FICA | 0.500 | ADD | 0.063 | SYN | 0.500 | IND | 0.500 | ADD | 0.250 | ADD | 0.500 | IND | 0.500 | IND | |||||||||||||||||||||||||||||
FICB | 0.500 | 0.125 | 1.000 | 0.500 | 0.500 | 1.000 | 2.000 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 1.000 | 0.188 | 1.500 | 1.000 | 0.750 | 1.500 | 2.500 | |||||||||||||||||||||||||||||||||||||
BOR + α-TER | FICA | 0.250 | SYN | 0.500 | ADD | 0.250 | ADD | 0.500 | ADD | 0.500 | IND | 0.500 | ADD | 0.124 | SYN | |||||||||||||||||||||||||||||
FICB | 0.250 | 0.250 | 0.500 | 0.250 | 1.000 | 0.500 | 0.124 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 0.500 | 0.750 | 0.750 | 0.750 | 1.500 | 1.000 | 0.248 | |||||||||||||||||||||||||||||||||||||
BOR + γ -TER | FICA | 0.250 | SYN | 0.500 | ADD | 0.500 | ADD | 0.500 | ADD | 0.500 | ADD | 0.250 | SYN | 2.000 | IND | |||||||||||||||||||||||||||||
FICB | 0.250 | 0.250 | 0.500 | 0.125 | 0.500 | 0.031 | 0.125 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 0.500 | 0.750 | 1.000 | 0.625 | 1.000 | 0.281 | 2.125 | |||||||||||||||||||||||||||||||||||||
α-TER + γ -TER | FICA | 0.500 | ADD | 0.500 | ADD | 0.500 | ADD | 0.125 | SYN | 0.500 | ADD | 1.000 | IND | 1.000 | IND | |||||||||||||||||||||||||||||
FICB | 0.250 | 0.250 | 0.250 | 0.125 | 0.250 | 0.125 | 0.016 | |||||||||||||||||||||||||||||||||||||
ƩFIC | 0.750 | 0.750 | 0.750 | 0.250 | 0.750 | 1.125 | 1.016 |
3. Experimental
3.1. Strains, Media and Chemicals
3.2. Gas Chromatography-Mass Spectrometry Analysis
3.3. Antimicrobial Susceptibility Tests
3.3.1. Determination of Minimal Inhibitory Concentration (MIC)
3.3.2. Assessment of the FIC Index
3.3.3. Varied Ratio Combinations and Isobolograms
4. Conclusions
Acknowledgments
Author Contributions
Conflictts of Interest
References
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Share and Cite
Ahmad, A.; Van Vuuren, S.; Viljoen, A. Unravelling the Complex Antimicrobial Interactions of Essential Oils — The Case of Thymus vulgaris (Thyme). Molecules 2014, 19, 2896-2910. https://doi.org/10.3390/molecules19032896
Ahmad A, Van Vuuren S, Viljoen A. Unravelling the Complex Antimicrobial Interactions of Essential Oils — The Case of Thymus vulgaris (Thyme). Molecules. 2014; 19(3):2896-2910. https://doi.org/10.3390/molecules19032896
Chicago/Turabian StyleAhmad, Aijaz, Sandy Van Vuuren, and Alvaro Viljoen. 2014. "Unravelling the Complex Antimicrobial Interactions of Essential Oils — The Case of Thymus vulgaris (Thyme)" Molecules 19, no. 3: 2896-2910. https://doi.org/10.3390/molecules19032896
APA StyleAhmad, A., Van Vuuren, S., & Viljoen, A. (2014). Unravelling the Complex Antimicrobial Interactions of Essential Oils — The Case of Thymus vulgaris (Thyme). Molecules, 19(3), 2896-2910. https://doi.org/10.3390/molecules19032896