Eucalyptol Explained

Eucalyptol (also called cineole) is a monoterpenoid colorless liquid, and a bicyclic ether.[1] It has a fresh camphor-like odor and a spicy, cooling taste.[1] It is insoluble in water, but miscible with organic solvents. Eucalyptol makes up about 70–90% of eucalyptus oil.[2] Eucalyptol forms crystalline adducts with hydrohalic acids, o-cresol, resorcinol, and phosphoric acid. Formation of these adducts is useful for purification.

In 1870, F. S. Cloez identified and ascribed the name "eucalyptol" to the dominant portion of Eucalyptus globulus oil.[3]

Uses

Because of its pleasant, spicy aroma and taste, eucalyptol is used in flavorings, fragrances, and cosmetics.[1] Cineole-based eucalyptus oil is used as a flavoring at low levels (0.002%) in various products, including baked goods, confectionery, meat products, and beverages.[1] [4] In a 1994 report released by five top cigarette companies, eucalyptol was listed as one of the 599 additives to cigarettes.[5] It is claimed to be added to improve the flavor.[1]

Eucalyptol is an ingredient in commercial mouthwashes,[1] and has been used in traditional medicine as a cough suppressant.[6]

Other

Eucalyptol exhibits insecticidal and insect repellent properties.[7] [8]

In contrast, eucalyptol is one of many compounds that are attractive to males of various species of orchid bees, which gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study.[9] One such study with Euglossa imperialis, a nonsocial orchid bee species, has shown that the presence of cineole (also eucalyptol) elevates territorial behavior and specifically attracts the male bees. It was even observed that these males would periodically leave their territories to forage for chemicals such as cineole, thought to be important for attracting and mating with females, to synthesize pheromones.[10]

Toxicology

Eucalyptol has a toxicity (LD50) of 2.48 grams per kg (rat).[1] Ingestion in significant quantities is likely to cause headache and gastric distress, such as nausea and vomiting.[1] Because of its low viscosity, it may directly enter the lungs if swallowed, or if subsequently vomited. Once in the lungs, it is difficult to remove and can cause delirium, convulsions, severe injury or death.[1]

Biosynthesis

Eucalyptol is generated from geranyl pyrophosphate (GPP) which isomerizes to (S)-linalyl diphosphate (LPP). Ionization of the pyrophosphate, catalyzed by cineole synthase, produces eucalyptol. The process involves the intermediacy of alpha-terpinyl cation.[11] [12] [13]  

Plants containing eucalyptol

See also

Notes and References

  1. Web site: Eucalyptol . PubChem, US National Library of Medicine . 28 April 2023 . 22 April 2023.
  2. Web site: GCMS – Gas Chromatography Mass Spectrometry Analysis . live . https://web.archive.org/web/20201028145542/https://www.newdirectionsaromatics.com/msds/GC_EucalyptusRadiataEssentialOil.pdf . 28 October 2020 . 7 December 2022 . New Direction Aromatics.
  3. Book: Boland . D. J. . Brophy . J. J. . House . A. P. N. . Eucalyptus Leaf Oils: Use, Chemistry, Distillation and Marketing . 1991 . 6 . 0-909605-69-6. Inkata Press . Melbourne . 10.1002/ffj.2730070209 .
  4. Book: Harborne . J. B. . Chemical Dictionary of Economic Plants . Baxter . H. . 30 August 2001 . John Wiley & Sons . 0-471-49226-4.
  5. Web site: Cigarette Ingredients – Chemicals in Cigarettes. New York State Department of Health. 28 July 2014.
  6. Web site: Tea tree oil . Drugs.com . 31 July 2019 . 17 June 2019.
  7. Klocke . J. A. . Darlington . M. V. . Balandrin . M. F. . 8-Cineole (Eucalyptol), a Mosquito Feeding and Ovipositional Repellent from Volatile Oil of Hemizonia fitchii (Asteraceae) . Journal of Chemical Ecology . 13 . 12 . December 1987 . 10.1007/BF01012562 . 24301652 . 2131–41 . 23271137 .
  8. 10.1603/033.046.0315 . Sfara . V. . Zerba . E. N. . Alzogaray . R. A. . Fumigant Insecticidal Activity and Repellent Effect of Five Essential Oils and Seven Monoterpenes on First-Instar Nymphs of Rhodnius prolixus . . 46 . 3 . 511–515 . May 2009 . 19496421 . 23452066 . 11336/82775 . free .
  9. Schiestl . F. P. . Roubik . D. W. . 2004 . Odor Compound Detection in Male Euglossine Bees . Journal of Chemical Ecology . 29 . 1 . 253–257 . 10.1023/A:1021932131526 . 12647866 . free . 20.500.11850/57276 . 2845587.
  10. Schemske. Douglas W.. Russell. Lande. Fragrance collection and territorial display by male orchid bees. Animal Behaviour. 32. 3. 1984. 935–937. 10.1016/s0003-3472(84)80184-0. 54411184.
  11. Rinkel . Jan . Rabe . Patrick . zur Horst . Laura . Dickschat . Jeroen S . 2016-11-04 . A Detailed View on 1,8-Cineol Biosynthesis by Streptomyces clavuligerus . Beilstein Journal of Organic Chemistry . 12 . 2317–2324 . 10.3762/bjoc.12.225 . 1860-5397 . 5238540 . 28144299.
  12. Wise . Mitchell L. . Savage . Thomas J. . Katahira . Eva . Croteau . Rodney . 1998-06-12 . Monoterpene Synthases From Common Sage (Salvia Officinalis): cDNA Isolation, Characterization, and Functional Expression of (+)-Aabinene Synthase, 1,8-Cineole Synthase, and (+)-Bo... . Journal of Biological Chemistry . en . 273 . 24 . 14891–14899 . 10.1074/jbc.273.24.14891 . 0021-9258. free .
  13. Croteau . R. . Alonso . W. R. . Koepp . A. E. . Johnson . M. A. . 1994-02-01 . Biosynthesis of Monoterpenes: Partial Purification, Characterization, and Mechanism of Action of 1,8-Cineole Synthase . Archives of Biochemistry and Biophysics . en . 309 . 1 . 184–192 . 10.1006/abbi.1994.1101 . 0003-9861.
  14. Sebsebe Demissew . A description of some essential oil bearing plants in Ethiopia and their indigenous uses . Journal of Essential Oil Research . 5 . 5 . 1993 . 465–479 . . 10.1080/10412905.1993.9698266 . The chemical composition of … Aframomum corrorima (l, 8-cineole 41.9%) … is also presented..
  15. Crowell, M.M.. etal. Dietary partitioning of toxic leaves and fibrous stems differs between sympatric specialist and generalist mammalian herbivores. Journal of Mammalogy . 99 . 3 . 565–577 . 2018 . 10.1093/jmammal/gyy018. free .
  16. McPartland . J. M. . Russo . E. B. . Cannabis and cannabis extracts: greater than the sum of their parts? . Journal of Cannabis Therapeutics . 1 . 3–4 . 103–132 . 2001 . 10.1300/J175v01n03_08 . 20 September 2013.
  17. Stubbs . B. J. . Brushett . D. . Leaf oil of Cinnamomum camphora (L.) Nees and Eberm. From Eastern Australia . Journal of Essential Oil Research . 13 . 1 . 51–54 . 2001 . 10.1080/10412905.2001.9699604. 85418932 .
  18. Maciel . M. V. . Morais . S. M. . Bevilaqua . C. M. . Silva . R. A. . Barros . R. S. . Sousa . R. N. . Sousa . L. C. . Brito . E. S. . Souza Neto . M. A. . 2010 . Chemical composition of Eucalyptus spp. essential oils and their insecticidal effects on Lutzomyia longipalpis . Veterinary Parasitology . 167 . 1 . 1–7 . 10.1016/j.vetpar.2009.09.053 . 19896276 . 7665066 .
  19. Chemistry and bioactivity of Eucalyptus essential oils. 25. 2. 313–330. 2010 . Allelopathy Journal. Zhang J, An M, Wu H, Stanton R, Lemerle D.
  20. Trees of Western Australia - salmon gum and scarlet pear gum. 23 January 2023. Journal of the Department of Agriculture Western Australia Series 3. Charles Austin Gardner. 1. 4. 1 August 1952. Department of Primary Industries and Regional Development.
  21. Gilles . M. . Zhao . J. . An . M. . Agboola . S. . 2010 . Chemical Composition and Antimicrobial Properties of Essential Oils of three Australian Eucalyptus Species . Food Chemistry . 119 . 2 . 731–737 . 10.1016/j.foodchem.2009.07.021 .
  22. Chemical composition of essential oils of eight Tunisian Eucalyptus species and their antibacterial activity against strains responsible for otitis. Ameur. Elaissi. Sarra. Moumni. Yosra. Derbali. Mariem. Kouja. Nabil. Abid. Lynen. Frederic. Larbi. Khouja Mohamed. BMC Complement Med Ther. 21. 2021. 1 . 209 . 10.1186/s12906-021-03379-y. 34384412 . 8359536 . free .
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