Thymol (also known as 2-isopropyl-5-methylphenol, IPMP) is a natural monoterpenoid phenol derivative of cymene, C10H14O, isomeric with carvacrol, found in oil of thyme, and extracted from Thymus vulgaris (common thyme), Ajwain 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.
|Preferred IUPAC name
|Systematic IUPAC name
2-Isopropyl-5-methylphenol, isopropyl-m-cresol, 1-methyl-3-hydroxy-4-isopropylbenzene, 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
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||150.221 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)|
|0.9 g/L (20 °C)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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.
- C7H8O + C3H6 ⇌ C10H14O
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.
An in vitro study found thymol and carvacrol to be highly effective in reducing the minimum inhibitory concentration of several antibiotics against zoonotic pathogens and food spoilage bacteria such as Salmonella typhimurium SGI 1 and Streptococcus pyogenes ermB. In vitro studies have found thymol to be useful as an antifungal against food spoilage and bovine mastitis. Thymol demonstrates in vitro post-antibacterial effect against the test strains E. coli and P. aeruginosa (gram negative), and Staphylococcus aureus and B. cereus (gram positive). This antibacterial activity is caused by inhibiting growth and lactate production, and by decreasing cellular glucose uptake.
Thyme essential oil is useful in preservation of food. The antibacterial properties of thymol, a major part of thyme essential oil, as well as other constituents, are in part associated with their lipophilic character, leading to accumulation in bacterial membranes and subsequent membrane-associated events, such as energy depletion.
The antifungal nature of thymol against some fungi that are pathogenic to plants is due to its ability to alter the hyphal morphology and cause hyphal aggregates, resulting in reduced hyphal diameters and lyses of the hyphal wall.
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. People of the Middle East continue to use za'atar, a delicacy made with large amounts of thyme, to reduce and eliminate internal parasites. 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 Johnson & Johnson's Euthymol. Thymol has been used to successfully control varroa mites and prevent fermentation and the growth of mold in bee colonies, methods developed by beekeeper R. O. B. Manley. Thymol is also used as a rapidly degrading, non-persisting pesticide. Thymol can also be used as a medical disinfectant and general purpose disinfectant.
List of plants that contain thymolEdit
- Euphrasia rostkoviana
- Monarda didyma
- Monarda fistulosa
- Mosla chinensis, Xiang Ru (香薷)
- Trachyspermum ammi
- Origanum compactum
- Origanum dictamnus
- Origanum onites
- Origanum vulgare
- Thymus glandulosus
- Thymus hyemalis
- Thymus vulgaris
- Thymus zygis
- Satureja thymbra
Toxicology and environmental impactsEdit
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 pesticideEdit
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 referencesEdit
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- 74 FR 12613
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