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][3] Eucalyptol forms crystalline adducts with hydrohalic acids, o-cresol, resorcinol, and phosphoric acid. Formation of these adducts is useful for purification.[4]

Eucalyptol
Names
IUPAC name
1,3,3-Trimethyl-2-oxabicyclo[2.2.2]octane
Other names
1,8-Cineole
1,8-Epoxy-p-menthane
cajeputol
1,8-epoxy-p-menthane, 1,8-oxido-p-menthane
eucalyptole
1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane
cineol
cineole.
Identifiers
3D model (JSmol)
105109 5239941
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.006.757 Edit this at Wikidata
EC Number
  • 207-431-5
131076
KEGG
UNII
  • InChI=1S/C10H18O/c1-9(2)8-4-6-10(3,11-9)7-5-8/h8H,4-7H2,1-3H3 checkY
    Key: WEEGYLXZBRQIMU-UHFFFAOYSA-N checkY
  • InChI=1/C10H18O/c1-9(2)8-4-6-10(3,11-9)7-5-8/h8H,4-7H2,1-3H3
    Key: WEEGYLXZBRQIMU-UHFFFAOYAY
  • O2C1(CCC(CC1)C2(C)C)C
Properties
C10H18O
Molar mass 154.249 g/mol
Density 0.9225 g/cm3
Melting point 2.9 °C (37.2 °F; 276.0 K)
Boiling point 176–177 °C (349–351 °F; 449–450 K)
−116.3×10−6 cm3/mol
Pharmacology
R05CA13 (WHO)
Hazards
GHS labelling:
GHS02: FlammableGHS07: Exclamation markGHS08: Health hazardGHS09: Environmental hazard
Danger
H226, H304, H315, H317, H319, H411
P210, P233, P240, P241, P242, P243, P261, P264, P272, P273, P280, P301+P310, P302+P352, P303+P361+P353, P305+P351+P338, P321, P331, P332+P313, P333+P313, P337+P313, P362, P363, P370+P378, P391, P403+P235, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

In 1870, F. S. Cloez identified and ascribed the name "eucalyptol" to the dominant portion of Eucalyptus globulus oil.[2]

Uses

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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][5] In a 1994 report released by five top cigarette companies, eucalyptol was listed as one of the 599 additives to cigarettes.[6] 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.[7]

Other

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Eucalyptol exhibits insecticidal and insect repellent properties.[8][9]

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.[10] 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.[11]

Toxicology

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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

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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.[12][13][14]   

Plants containing eucalyptol

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See also

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References

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  2. ^ a b Boland, D. J.; Brophy, J. J.; House, A. P. N. (1991). Eucalyptus Leaf Oils: Use, Chemistry, Distillation and Marketing. Melbourne: Inkata Press. p. 6. doi:10.1002/ffj.2730070209. ISBN 0-909605-69-6.
  3. ^ "GCMS – Gas Chromatography Mass Spectrometry Analysis" (PDF). New Direction Aromatics. Archived (PDF) from the original on 28 October 2020. Retrieved 7 December 2022.
  4. ^ Eggersdorfer, Manfred (2000). "Terpenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a26_205. ISBN 978-3527306732.
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  6. ^ "Cigarette Ingredients – Chemicals in Cigarettes". New York State Department of Health. Retrieved 28 July 2014.
  7. ^ "Tea tree oil". Drugs.com. 17 June 2019. Retrieved 31 July 2019.
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