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Thymol

Not to be confused with Thymeol, Thymine, or Thiamine.

Thymol
Thymol
Names
Preferred IUPAC name
5-Methyl-2-(propan-2-yl)phenol[1]
Systematic IUPAC name
5-Methyl-2-(propan-2-yl)benzenol
Other names
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
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.001.768 Edit this at Wikidata
EC Number
  • 201-944-8
KEGG
UNII
  • InChI=1S/C10H14O/c1-7(2)9-5-4-8(3)6-10(9)11/h4-7,11H,1-3H3 checkY
    Key: MGSRCZKZVOBKFT-UHFFFAOYSA-N checkY
  • 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 150.221 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)
0.9 g/L (20 °C)[2]
1.5208[3]
Pharmacology
QP53AX22 (WHO)
Hazards
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation markGHS09: Environmental hazard
Warning
H302, H314, H411
P260, P264, P270, P273, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P330, P363, P391, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Thymol (also known as 2-isopropyl-5-methylphenol, IPMP), C10H14O, is a natural monoterpenoid phenol derivative of p-Cymene, isomeric with carvacrol, found in oil of thyme, and extracted from Thymus vulgaris (common thyme), ajwain,[4] and various other 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 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. Its dissociation constant (pKa) is 10.59±0.10.[5] Thymol absorbs maximum UV radiation at 274 nm.[6]

Chemical synthesis

Thymol is produced by the alkylation of m-cresol and propene:[7][8]

CH3C6H4OH + CH2CHCH3 → ((CH3)2CH)CH3C6H3OH

A predicted method of biosynthesis of thymol in thyme and oregano begins with the cyclization of geranyl diphosphate by TvTPS2 to γ-terpinene. Oxidation by a cytochrome P450 in the CYP71D subfamily creates a dienol intermediate, which is then converted into a ketone by short-chain dehydrogenase. Lastly, keto-enol tautomerization gives thymol.

Predicted biosynthesis of thymol in thyme and oregano. Reconstruction of figure 4 in Krause et. al. (2021).[9]

History

Ancient Egyptians used thyme for embalming.[10] The ancient Greeks used it in their baths and burned it as incense in their temples, believing it was a source of courage. The spread of thyme throughout Europe was thought to be due to the Romans, as they used it to purify their rooms and to "give an aromatic flavour to cheese and liqueurs".[11] In the European Middle Ages, the herb was placed beneath pillows to aid sleep and ward off nightmares.[12] In this period, women also often gave knights and warriors gifts that included thyme leaves, because it was believed to bring courage to the bearer. Thyme was also used as incense and placed on coffins during funerals, because it was supposed to ensure passage into the next life.[13]

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.[14]

Thymol was first isolated by German chemist Caspar Neumann in 1719.[15] In 1853, French chemist Alexandre Lallemand[16] (1816-1886) named thymol and determined its empirical formula.[17] Antiseptic properties of thymol were discovered in 1875,[18] and it was first synthesized by Swedish chemist Oskar Widman[19] (1852-1930) in 1882.[20]

Extraction

The conventional method of extracting is hydro-distillation (HD), but can also be extracted with solvent-free microwave extraction (SFME). In 30 minutes, SFME yields similar amounts of thymol with more oxygenated compounds than 4.5 hours of hydro-distillation at atmospheric pressures without the need for solvent.[21]

Uses

Thymol

Thymol during the 1910s was the treatment of choice for hookworm infection in the United States.[22][23] People of the Middle East continue to use za'atar, a delicacy made with large amounts of thyme, to reduce and eliminate internal parasites.[24] 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.[25] 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.[26] Thymol is also used as a rapidly degrading, non-persisting pesticides[27] such as insecticides and fungicides which are leveraged in plant care products, where its environmentally friendly, rapid degradation ensures it doesn’t leave persistent residues while effectively controlling pests and fungal issues.[28] Thymol can also be used as a medical disinfectant and general purpose disinfectant.[29] Thymol is also used in the production of menthol through the hydrogenation of the aromatic ring.[30]

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".[45]

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[27]) in the environment and are, thus, low risks because of rapid dissipation and low bound residues,[27] 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. Though, there has been recent research into sustained released systems for botanically derived pesticides, such as using natural polysaccharides which would be biodegradable and biocompatible.[46]

Compendial status

See also

Notes and references

  1. ^ "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 691. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^ "Thymol". PubChem. Retrieved 1 April 2016.
  3. ^ Mndzhoyan, A. L. (1940). "Thymol from Thymus kotschyanus". Sbornik Trudov Armyanskogo Filial. Akad. Nauk. 1940: 25–28.
  4. ^ O'Connell, John (27 August 2019). The book of spice : from anise to zedoary. New York: Pegasus. ISBN 978-1681774459. OCLC 959875923.
  5. ^ CAS Registry: Data obtained from SciFinder[full citation needed]
  6. ^ 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.
  7. ^ Stroh, R.; Sydel, R.; Hahn, W. (1963). Foerst, Wilhelm (ed.). Newer Methods of Preparative Organic Chemistry, Volume 2 (1st ed.). New York: Academic Press. p. 344. ISBN 9780323150422.
  8. ^ Fiege, Helmut; Voges, Heinz-Werner; Hamamoto, Toshikazu; Umemura, Sumio; Iwata, Tadao; Miki, Hisaya; Fujita, Yasuhiro; Buysch, Hans-Josef; Garbe, Dorothea; Paulus, Wilfried (2000). "Phenol Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_313. ISBN 3527306730.
  9. ^ Krause, Sandra T.; Liao, Pan; Crocoll, Christoph; Boachon, Benoît; Förster, Christiane; Leidecker, Franziska; Wiese, Natalie; Zhao, Dongyan; Wood, Joshua C.; Buell, C. Robin; Gershenzon, Jonathan; Dudareva, Natalia; Degenhardt, Jörg (28 December 2021). "The biosynthesis of thymol, carvacrol, and thymohydroquinone in Lamiaceae proceeds via cytochrome P450s and a short-chain dehydrogenase". Proceedings of the National Academy of Sciences. 118 (52). doi:10.1073/pnas.2110092118. ISSN 0027-8424. PMC 8719858. PMID 34930840.
  10. ^ "A Brief History of Thyme - Hungry History". HISTORY.com. Archived from the original on 13 June 2016. Retrieved 9 June 2016.
  11. ^ Grieve, Mrs. Maud. "Thyme. A Modern Herbal". botanical.com (Hypertext version of the 1931 ed.). Archived from the original on 23 February 2011. Retrieved 9 February 2008.
  12. ^ Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan.
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  15. ^ Neuman, Carolo (1724). "De Camphora". Philosophical Transactions of the Royal Society of London. 33 (389): 321–332. doi:10.1098/rstl.1724.0061. On page 324, Neumann mentions that in 1719 he distilled some essential oils from various herbs. On page 326, he mentions that during 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.)
  16. ^ Marie-Étienne-Alexandre Lallemand (December 25, 1816 - March 16, 1886)
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  18. ^ Oettingen, Wolfgang Felix Von (1949). Phenol and Its Derivatives: The Relation Between Their Chemical Constitution and Their Effect on the Organism. U.S. Government Printing Office. ISBN 978-0-598-95964-5.
  19. ^ Karl Oskar Widman (aka Carl Oskar Widman) (January 2, 1852 - August 26, 1930)
  20. ^ Widmann, Oskar (1882). "Ueber eine Synthese von Thymol aus Cuminol" [On a synthesis of thymol from cuminol]. Berichte der Deutschen Chemischen Gesellschaft zu Berlin (in German). 15: 166–172. doi:10.1002/cber.18820150139.
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  22. ^ Ferrell, John Atkinson (1914). The Rural School and Hookworm Disease. US Bureau of Education Bulletin. Vol. 20, Whole No. 593. Washington, DC: U.S. Government Printing Office.
  23. ^ Milton, Joseph Rosenau (1913). Preventive Medicine and Hygiene. D. Appleton. p. 119.
  24. ^ Inskeep, Steve; Godoy, Maria (11 June 2013). "Za'atar: A Spice Mix With Biblical Roots And Brain Food Reputation". NPR. Retrieved 24 February 2022.
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  26. ^ Ward, Mark (8 March 2006). "Almond farmers seek healthy bees". BBC News. BBC.
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  28. ^ "T-Guard: The Ultimate Insect Fungus Control Product". GrowScripts Plant Food Fertilizer. Retrieved 7 October 2024.
  29. ^ "Thymol" (PDF). US Environmental Protection Agency. September 1993.
  30. ^ "Menthol | Definition, Structure, & Uses | Britannica". www.britannica.com. 6 October 2023. Retrieved 30 October 2023.
  31. ^ Novy, P.; Davidova, H.; Serrano Rojero, C. S.; Rondevaldova, J.; Pulkrabek, J.; Kokoska, L. (2015). "Composition and Antimicrobial Activity of Euphrasia rostkoviana Hayne Essential Oil". Evid Based Complement Alternat Med. 2015: 1–5. doi:10.1155/2015/734101. PMC 4427012. PMID 26000025.
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  33. ^ Donata Ricci; Francesco Epifano; Daniele Fraternale (February 2017). Olga Tzakou (ed.). "The Essential Oil of Monarda didyma L. (Lamiaceae) Exerts Phytotoxic Activity In Vitro against Various Weed Seeds". Molecules (Basel, Switzerland). 22 (2). Molecules: 222. doi:10.3390/molecules22020222. PMC 6155892. PMID 28157176.
  34. ^ Zamureenko, V. A.; Klyuev, N. A.; Bocharov, B. V.; Kabanov, V. S.; Zakharov, A. M. (1989). "An investigation of the component composition of the essential oil of Monarda fistulosa". Chemistry of Natural Compounds. 25 (5): 549–551. doi:10.1007/BF00598073. ISSN 1573-8388. S2CID 24267822.
  35. ^ Escobar, Angélica; Pérez, Miriam; Romanelli, Gustavo; Blustein, Guillermo (1 December 2020). "Thymol bioactivity: A review focusing on practical applications". Arabian Journal of Chemistry. 13 (12): 9243–9269. doi:10.1016/j.arabjc.2020.11.009. hdl:11336/139451. ISSN 1878-5352.
  36. ^ a b Bouchra, Chebli; Achouri, Mohamed; Idrissi Hassani, L. M.; Hmamouchi, Mohamed (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.
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  38. ^ Ozkan, Gulcan; Baydar, H.; Erbas, S. (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.
  39. ^ Lagouri, Vasiliki; Blekas, George; Tsimidou, Maria; Kokkini, Stella; Boskou, Dimitrios (1993). "Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece". Zeitschrift für Lebensmittel-Untersuchung und -Forschung A. 197 (1): 1431–4630. doi:10.1007/BF01202694. S2CID 81307357.
  40. ^ Kanias, G. D.; Souleles, C.; Loukis, A.; Philotheou-Panou, E. (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. S2CID 94582250.
  41. ^ Figiel, Adam; Szumny, Antoni; Gutiérrez Ortíz, Antonio; Carbonell Barrachina, Ángel A. (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.
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