|Molar mass||150.22 g·mol−1|
|Melting point||49 to 51 °C (120 to 124 °F; 322 to 324 K)|
|Boiling point||232 °C (450 °F; 505 K)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is: / ?)(|
Thymol (also known as 2-isopropyl-5-methylphenol, IPMP) is a natural monoterpene phenol derivative of cymene, C10H14O, isomeric with carvacrol, found in oil of thyme, and extracted from Thymus vulgaris (common thyme) and various other kinds of plants as a white crystalline substance of a pleasant aromatic odor and strong antiseptic properties. Thymol also provides the distinctive, strong flavor of the culinary herb thyme, also produced from T. vulgaris.
Thymol is part of a naturally occurring class of compounds known as biocides, with strong antimicrobial attributes when used alone or with other biocides such as carvacrol. In addition, naturally occurring biocidal agents such as thymol can reduce bacterial resistance to common drugs such as penicillin. Numerous studies have demonstrated the antimicrobial effects of thymol, ranging from inducing antibiotic susceptibility in drug-resistant pathogens to powerful antioxidant properties. Research demonstrates that naturally occurring biocides such as thymol and carvacrol reduce bacterial resistance to antibiotics through a synergistic effect, and thymol has been shown to be an effective fungicide, particularly against fluconazole-resistant strains. This is especially relevant given that opportunistic Candida fungal infections can cause severe systemic infections in immunocompromised patients, and current treatments are highly toxic, often result in drug-resistant Candida strains, and have low efficacy. Compounds in the essential oils of one type of oregano have demonstrated antimutagenic effects, and in particular carvacrol (isomeric with thymol) and thymol were demonstrated to have a strong antimutagenic effect. In addition, there is evidence that thymol has antitumor properties. Though the exact mechanism is unknown, some evidence suggests thymol effects at least some of its biocidal properties by membrane disruption.
Thymol is only slightly soluble in water at neutral pH, but it is extremely soluble in alcohols and other organic solvents. It is also soluble in strongly alkaline aqueous solutions due to deprotonation of the phenol.
Synonyms include isopropyl-m-cresol, cymene, 1-methyl-3-4-isopropylbenzene, 2--1-isopropyl-4-methylbenzene; 3-p-cymene, 3-methyl-6-isopropylphenol, 5-methyl-2-(1-methylethyl)phenol, 5-methyl-2-isopropyl-1-phenol, 5-methyl-2-isopropylphenol, 6-isopropyl-3-methylphenol, 6-isopropyl-m-cresol, Apiguard, NSC 11215, NSC 47821, NSC 49142, thyme camphor, m-thymol, and p-cymen-3-ol.
The Ancient Egyptians used thymol and carvacrol in the form of a preparation from the thyme plant (a member of the mint family) to preserve mummies. Thymol and carvacrol are now known to kill bacteria and fungi, making thyme well suited for such purposes.
In Ancient Greece, thyme was widely used for its aromatic qualities, being burned as incense in sacred temples. Thyme was also a symbol of courage and admiration, with the phrase "the smell of thyme" being a saying that reflected praise unto its subject. Thyme's association with bravery continued throughout medieval times, when it was a ritual for women to give their knights a scarf that had a sprig of thyme placed over an embroidered bee. Since the 16th century, thyme oil has been used for its antiseptic properties, both as mouthwash and for topical application.
The bee balms Monarda fistulosa and Monarda didyma, North American wildflowers, are natural sources of thymol. The Blackfoot Native Americans recognized these plants' strong antiseptic action, and used poultices of the plants for skin infections and minor wounds. A tisane made from them was also used to treat mouth and throat infections caused by dental caries and gingivitis.
Thymol was first isolated by the German chemist Caspar Neumann in 1719. In 1853, the French chemist A. Lallemand named thymol and determined its empirical formula. Thymol was first synthesized by the Swedish chemist Oskar Widman in 1882. Alain Thozet and M. Perrin first published the crystal structure analysis with the exact determination of the structural atoms.
Thymol has antimicrobial activity because of its phenolic structure, and has shown antibacterial activity against bacterial strains including Aeromoans hydrophila and Staphylococcus aureus. In addition Thymol demonstrate confidential post antibacterial effect against some microorganisms. This antibacterial activity is caused by inhibiting growth and lactate production, and by decreasing cellular glucose uptake. Thymol has been used in alcohol solutions and in dusting powders for the treatment of tinea or ringworm infections, and was used in the United States to treat hookworm infections. It is also used as a preservative in halothane, an anaesthetic, and as an antiseptic in mouthwash. When used to reduce plaque and gingivitis, thymol has been found to be more effective when used in combination with chlorhexidine than when used purely by itself. Thymol is also the active antiseptic ingredient in some toothpastes, such as Euthymol.
The antifungal nature of thymol is caused by thymol's ability to alter the hyphal morphology and cause hyphal aggregates, resulting in reduced hyphal diameters and lyses of hyphal wall. Additionally, thymol is lipophilic, enabling it to interact with the cell membrane of fungus cells, altering cell membrane permeability permitting the loss of macromolecules.
Derivatives of thymol and carvacrol with increased antimicrobial activities have been developed. The preparation of methacrylic and p-styrenesulfonic acid esters of thymol could lead to less toxic macromolecular biocides, which can be attached to a polymeric backbone.
A minor use of thymol is in book and paper conservation: Paper with mold damage can be sealed in bags with thymol crystals to kill fungal spores. However, this practice is not currently recommended due to apparent accelerated degradation suffered by these objects.
Thymol can also be used as a medical disinfectant and general purpose disinfectant. 
List of plants that contain thymol
- Euphrasia rostkoviana
- Monarda didyma
- Monarda fistulosa
- Trachyspermum ammi
- Origanum compactum
- Origanum dictamnus
- Origanum onites
- Origanum vulgare
- Thymus glandulosus
- Thymus hyemalis
- Thymus vulgaris
- Thymus zygis
Toxicology and environmental impacts
In 2009, the U.S. Environmental Protection Agency (EPA) reviewed the research literature on the toxicology and environmental impact of thymol and concluded that "thymol has minimal potential toxicity and poses minimal risk".
Environmental breakdown and use as a pesticide
Studies have shown that hydrocarbon monoterpenes and thymol in particular degrade rapidly (DT50 16 days in water, 5 days in soil) in the environment and are, thus, low risks because of rapid dissipation and low bound residues, supporting the use of thymol as a pesticide agent that offers a safe alternative to other more persistent chemical pesticides that can be dispersed in runoff and produce subsequent contamination.
Notes and references
- CRC Handbook of Chemistry and Physics, 1977
- Palaniappan, Kavitha; Holley, Richard A. (2010). "Use of natural antimicrobials to increase antibiotic susceptibility of drug resistant bacteria". International Journal of Food Microbiology 140 (2–3): 164–8. doi:10.1016/j.ijfoodmicro.2010.04.001. PMID 20457472..
- Zarrini G, Bahari-Delgosha Z, Mollazadeh-Moghaddam K, Shahverdi AR (2010). "Post-antibacterial effect of thymol". Pharmaceutical biology 48 (6): 633–636. doi:10.3109/13880200903229098. PMID 20645735.
- Ündeğer, Ü.; Başaran, A.; Degen, G. H.; Başaran, N. (Aug 2009). "Antioxidant activities of major thyme ingredients and lack of (oxidative) DNA damage in V79 Chinese hamster lung fibroblast cells at low levels of carvacrol and thymol". Food and Chemical Toxicology 47 (8): 2037–2043. doi:10.1016/j.fct.2009.05.020. PMID 19477215.
- Ahmad A, et al, Proton translocating ATPase mediated fungicidal activity of eugenol and thymol,Fitoterapia (2010), doi:10.1016/j.fitote.2010.07.020
- Mezzoug, N.; Elhadri, A.; Dallouh, A.; Amkiss, S.; Skali, N.S.; Abrini, J.; Zhiri, A.; Baudoux, D.; Diallo, B.; El Jaziri, M.; Idaomar, M. (2007). "Investigation of the mutagenic and antimutagenic effects of Origanum compactum essential oil and some of its constituents". Mutation Research/Genetic Toxicology and Environmental Mutagenesis 629 (2): 100. doi:10.1016/j.mrgentox.2007.01.011.
- Andersen, A (2006). "Final report on the safety assessment of sodium p-chloro-m-cresol, p-chloro-m-cresol, chlorothymol, mixed cresols, m-cresol, o-cresol, p-cresol, isopropyl cresols, thymol, o-cymen-5-ol, and carvacrol". International journal of toxicology. 25 Suppl 1: 29–127. doi:10.1080/10915810600716653. PMID 16835130.
- Trombetta, D.; Castelli, F.; Sarpietro, M. G.; Venuti, V.; Cristani, M.; Daniele, C.; Saija, A.; Mazzanti, G.; Bisignano, G. (2005). "Mechanisms of Antibacterial Action of Three Monoterpenes". Antimicrobial Agents and Chemotherapy 49 (6): 2474–8. doi:10.1128/AAC.49.6.2474-2478.2005. PMC 1140516. PMID 15917549.
- García DA, Bujons J, Vale C, Suñol C (Sep 26, 2005). "Allosteric positive interaction of thymol with the GABAA receptor in primary cultures of mouse cortical neurons.". Neuropharmacology 50 (1): 25–35. doi:10.1016/j.neuropharm.2005.07.009. PMID 16185724.
- Webster's 1913 dictionary
- CAS Registry: Data were obtained from SciFinder
- Mndzhoyan, A. L. Thymol from Thymus kotschyanus. Sbornik Trudov Armyanskogo Filial. Akad. Nauk. 1940, 25-28.
- CAS Registry: Data were obtained from SciFinder
- Norwitz, G.; Nataro, N.; Keliher, P. N. (1986). "Study of the Steam Distillation of Phenolic Compounds Using Ultraviolent Spectrometry". Anal. Chem 58 (639–640): 641. doi:10.1021/ac00294a034.
- Tilford, Gregory L. (1997) Edible and Medicinal Plants of the West. Missoula, MT: Mountain Press Publishing. ISBN 0-87842-359-1
- Carolo Neuman (1724) "De Camphora," Philosophical Transactions of the Royal Society of London, 33 (389) : 321-332. Available on-line at: Royal Society. On page 324, Neumann mentions that in 1719 (MDCCXIX) he distilled some essential oils from various herbs. On page 326, he mentions that during the course of these experiments, he obtained a crystalline substance from thyme oil, which he called "Camphora Thymi" (camphor of thyme). (Neumann gave the name "camphor" not only to the specific substance that today is called camphor, but to any crystalline substance that precipitated from a volatile, fragrant oil from some plant.)
- A. Lallemand (1853) "Sur la composition de l'huile essentielle de thym" (On the composition of the essential oil of thyme), Comptes rendus, 37 : 498-500. (Note that Lallemand's empirical formula for thymol is incorrect because chemists at that time used the wrong atomic masses for carbon and oxygen.)
- Oskar Widmann (1882) "Ueber eine Synthese von Thymol aus Cuminol" (On a synthesis of thymol from cuminol), Berichte der Deutschen chemischen Gesellschaft zu Berlin, 15 : 166-172.
- Dorman, H.J.D.; Deans, S.G. (2000). "Antimicrobial agents from plants: antibacterial activity of plant volatile oils". J. Appl. Microbiol 88 (2): 308–316. doi:10.1046/j.1365-2672.2000.00969.x. PMID 10736000.
- Evans, J.; Martin, J. D. (2000). "Effects of thymol on ruminal microorganisms". Curr. Microbiol 41 (5): 336. doi:10.1007/s002840010145.
- Ferrell, John Atkinson (1914). The Rural School and Hookworm Disease. US Bureau of Education Bulletin. No. 20, Whole No. 593. Washington, DC: U.S. Government Printing Office.
- Filoche, S.K.; Soma, K.; Sissons, C.H. (2005). "Antimicrobial effects of essential oils in combination with chlorhexidine digluconate". Oral Microbiol Immunol 20 (4): 221–225. doi:10.1111/j.1399-302X.2005.00216.x. PMID 15943766.
- Numpaque, M. A.; Oviedo, L. A.; Gil, J. H.; García, C. M.; Durango, D. L. (2011). "Thymol and carvacrol: biotransformation and antifungal activity against the plant pathogenic fungi Colletotrichum acutatum and Botryodiplodia theobromae". Trop. Plant Pathol 36: 3–13. doi:10.1590/S1982-56762011000100001.
- Segvic Klaric, M.; Kosalec, I.; Mastelic, J.; Pieckova, E.; Pepeljnak, S. Antifungal activity of thyme (Thymus vulgaris L.) essential oil and thymol against moulds from damp dwellings Lett. Appl. Microbiol. 2007, 44, 36-42.
- Wienkötter, N.; F. Begrow; U. Kinzinger; D. Schierstedt; E.J. Verspohl (2007). "The Effect of Thyme Extract on β2-Receptors and Mucociliary Clearance". Planta Medica 73 (7): 629–635. doi:10.1055/s-2007-981535. PMID 17564943.
- Cigarette Ingredients - Chemicals in Tobacco Smoke. Tri-County Cessation Center. New York State Department of Health Tobacco Control Program.
- Ward, Mark. (2006-03-08) Almond farmers seek healthy bees. BBC News.
- D. Hu and J. Coats, Evaluation of the environmental fate of thymol and phenethyl propionate in the laboratory, Pest Manag Sci 64:775–779 (2008) doi:10.1002/ps.1555
- Mathela, CS; Singh, KK; Gupta, VK (2010). "Synthesis and in-vitro antibacterial activity of thymol and carvacrol derivatives" (PDF). Acta Poloniae Pharmaceutica 67 (4): 375–380. PMID 20635533.
- N. Moszner, U. Salz, V. Rheinberger (1994) "Synthesis and polymerization of unsaturated derivatives of thymol". Polymer Bulletin 33 (1) 7-12. doi:10.1007/BF00313467
- P. Novy, H. Davidova, C. S. Serrano-Rojero, J. Rondevaldova, J. Pulkrabek, L. Kokoska, "Composition and Antimicrobial Activity of Euphrasia rostkoviana Hayne Essential Oil." Evididence Based Complementary and Alternative Medicine, April 27, 2015.
- V. A. Zamureenko, N. A. Klyuev, B. V. Bocharov, V. S. Kabanov and A. M. Zakharov, "An investigation of the component composition of the essential oil of Monarda fistulosa", Chemistry of Natural Compounds, Vol. 25, No. 5, Sep. 1989.
- Bouchra, Chebli; Achouri, Mohamed; Idrissi Hassani, L.M; Hmamouchi, Mohamed et al. (2003). "Chemical composition and antifungal activity of essential oils of seven Moroccan Labiatae against Botrytis cinerea Pers: Fr". Journal of Ethnopharmacology 89 (1): 165–169. doi:10.1016/S0378-8741(03)00275-7. PMID 14522450.
- Liolios, C.C.; Gortzi, O; Lalas, S; Tsaknis, J; Chinou, I et al. (2009). "Liposomal incorporation of carvacrol and thymol isolated from the essential oil of Origanum dictamnus L. and in vitro antimicrobial activity". Food Chemistry (Elsevier) 112 (1): 77–83. doi:10.1016/j.foodchem.2008.05.060.
- Ozkan, Gulcan; Baydar, H; Erbas, S et al. (2009). "The influence of harvest time on essential oil composition, phenolic constituents and antioxidant properties of Turkish oregano (Origanum onites L.)". Journal of the Science of Food and Agriculture 90 (2): 205–209. doi:10.1002/jsfa.3788. PMID 20355032.
- Lagouri, Vasiliki; Blekas, George; Tsimidou, Maria; Kokkini, Stella; Boskou, Dimitrios et al. (1993). "Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece". Zeitschrift für Lebensmitteluntersuchung und -Forschung A 197 (1): 1431–4630. doi:10.1007/BF01202694.
- Kanias, G. D.; Souleles, C.; Loukis, A.; Philotheou-Panou, E. et al. (1998). "Trace elements and essential oil composition in chemotypes of the aromatic plant Origanum vulgare". Journal of Radioanalytical and Nuclear Chemistry 227 (1 – 2): 23–31. doi:10.1007/BF02386426.
- Figiel, Adam; Szumny, Antoni; Gutiérrez-Ortíz, Antonio; Carbonell-Barrachina, ÁNgel A. et al. (2010). "Composition of oregano essential oil (Origanum vulgare) as affected by drying method". Journal of Food Engineering 98 (2): 240–247. doi:10.1016/j.jfoodeng.2010.01.002.
- Goodner, K.L.; Mahattanatawee, K; Plotto, A; Sotomayor, J; Jordan, M et al. (2006). "Aromatic profiles of Thymus hyemalis and Spanish T. vulgaris essential oils by GC–MS/GC–O". Industrial Crops and Products 24 (3): 264–268. doi:10.1016/j.indcrop.2006.06.006.
- Lee, Seung-Joo; Umano, K; Shibamoto, T; Lee, K et al. (2005). "Identification of volatile components in basil (Ocimum basilicum L.) and thyme leaves (Thymus vulgaris L.) and their antioxidant properties". Food Chemistry 91 (1): 131–137. doi:10.1016/j.foodchem.2004.05.056.
- Moldão-Martins, M.; Palavra, A; Beiraodacosta, M; Bernardogil, M et al. (2000). "Supercritical CO2 extraction of Thymus zygis L. subsp. sylvestris aroma". The Journal of Supercritical Fluids 18 (1): 25–34. doi:10.1016/S0896-8446(00)00047-4.
- 74 FR 12613
- The British Pharmacopoeia Secretariat (2009). "Index, BP 2009" (PDF). Retrieved 5 July 2009.
- "Japanese Pharmacopoeia" (PDF). Retrieved 21 April 2010.
|Wikimedia Commons has media related to Thymol.|