Thymol

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Thymol
Thymol
Thymol3D.png
Names
IUPAC name
2-isopropyl-5-methylphenol
Identifiers
89-83-8 YesY
ChEBI CHEBI:27607 YesY
ChEMBL ChEMBL29411 YesY
ChemSpider 21105998 YesY
DrugBank DB02513 YesY
2499
Jmol 3D model Interactive image
KEGG D01039 YesY
UNII 3J50XA376E YesY
  • InChI=1S/C10H14O/c1-7(2)9-5-4-8(3)6-10(9)11/h4-7,11H,1-3H3 YesY
    Key: MGSRCZKZVOBKFT-UHFFFAOYSA-N YesY
  • InChI=1/C10H14O/c1-7(2)9-5-4-8(3)6-10(9)11/h4-7,11H,1-3H3
    Key: MGSRCZKZVOBKFT-UHFFFAOYAS
  • CC(C)c1ccc(C)cc1O
Properties
C10H14O
Molar mass 150.22 g·mol−1
Density 0.96 g/cm3
Melting point 49 to 51 °C (120 to 124 °F; 322 to 324 K)
Boiling point 232 °C (450 °F; 505 K)
Insoluble[1]
Pharmacology
ATCvet code QP53AX22
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

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.

Biological activity

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.[2] Numerous studies have demonstrated the antimicrobial effects of thymol, ranging from inducing antibiotic susceptibility in drug-resistant pathogens to powerful antioxidant properties.[3][4] Research demonstrates that naturally occurring biocides such as thymol and carvacrol reduce bacterial resistance to antibiotics through a synergistic effect,[2] and thymol has been shown to be an effective fungicide,[5] 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.[6] In addition, there is evidence that thymol has antitumor properties.[7] Though the exact mechanism is unknown, some evidence suggests thymol effects at least some of its biocidal properties by membrane disruption.[8]

Thymol has been shown to act as a positive allosteric modulator of GABAA in vitro.[9] Thymol is chemically related to the anesthetic propofol.

Chemistry

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,[10] 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.[11]

Thymol has a refractive index of 1.5208[12] and an experimental dissociation exponent (pKa) of 10.59 ± 0.10.[13] Thymol absorbs maximum UV radiation at 274 nm.[14]

History

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.[citation needed] 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.[citation needed] 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.[15]

Thymol was first isolated by the German chemist Caspar Neumann in 1719.[16] In 1853, the French chemist A. Lallemand named thymol and determined its empirical formula.[17] Thymol was first synthesized by the Swedish chemist Oskar Widman in 1882.[18] Alain Thozet and M. Perrin first published the crystal structure analysis with the exact determination of the structural atoms.

Uses

Thymol

Thymol has antimicrobial activity because of its phenolic structure, and has shown antibacterial activity against bacterial strains including Aeromoans hydrophila and Staphylococcus aureus.[19] In addition, thymol demonstrates considerable post antibacterial effect against some microorganisms.[3] This antibacterial activity is caused by inhibiting growth and lactate production, and by decreasing cellular glucose uptake.[20] 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.[21] 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.[22] 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.[23] Additionally, thymol is lipophilic, enabling it to interact with the cell membrane of fungus cells, altering cell membrane permeability permitting the loss of macromolecules.[24]

Recent medical research on rats concludes that "Thyme extract had relaxing effects on organs possessing β2-receptors (uterus and trachea)."[25]

In a 1994 report released by five major cigarette companies, thymol was listed as one of 599 additives to cigarettes.[26][verification needed]

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.[27]

Thymol is also used as a rapidly degrading, non-persisting pesticide.[28]

Derivatives of thymol and carvacrol with increased antimicrobial activities have been developed.[29] 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.[30]

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.[citation needed]

Thymol can also be used as a medical disinfectant and general purpose disinfectant.[31]

List of plants that contain thymol

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".[43]

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[28]) in the environment and are, thus, low risks because of rapid dissipation and low bound residues,[28] 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.

Compendial status

See also

Notes and references

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External links

  1. ↑ CRC Handbook of Chemistry and Physics, 1977
  2. ↑ 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found..
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Ahmad A, et al, Proton translocating ATPase mediated fungicidal activity of eugenol and thymol,Fitoterapia (2010), doi:10.1016/j.fitote.2010.07.020
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Webster's 1913 dictionary
  11. ↑ CAS Registry: Data were obtained from SciFinder
  12. ↑ Mndzhoyan, A. L. Thymol from Thymus kotschyanus. Sbornik Trudov Armyanskogo Filial. Akad. Nauk. 1940, 25-28.
  13. ↑ CAS Registry: Data were obtained from SciFinder
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Tilford, Gregory L. (1997) Edible and Medicinal Plants of the West. Missoula, MT: Mountain Press Publishing. ISBN 0-87842-359-1
  16. ↑ 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.)
  17. ↑ 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.)
  18. ↑ 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.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  24. ↑ 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.
  25. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  26. ↑ Cigarette Ingredients - Chemicals in Tobacco Smoke. Tri-County Cessation Center. New York State Department of Health Tobacco Control Program.
  27. ↑ Ward, Mark. (2006-03-08) Almond farmers seek healthy bees. BBC News.
  28. ↑ 28.0 28.1 28.2 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
  29. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  30. ↑ 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
  31. ↑ http://archive.epa.gov/pesticides/reregistration/web/pdf/3143fact.pdf
  32. ↑ 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.
  33. ↑ 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.
  34. ↑ 34.0 34.1 Lua error in package.lua at line 80: module 'strict' not found.
  35. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  36. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  37. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  38. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  39. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  40. ↑ 40.0 40.1 Lua error in package.lua at line 80: module 'strict' not found.
  41. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  42. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  43. ↑ 74 FR 12613
  44. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  45. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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