Borneol is abicyclicorganic compound and aterpene derivative. Thehydroxyl group in this compound is placed in anendo position. The exo diastereomer is calledisoborneol. Being chiral, borneol exists asenantiomers, both of which are found in nature:d-borneol (also written (+)-borneol, dextroborneol, dexborneol) andl-borneol (or (−)-borneol, levoborneol).
Both borneol and isoborneol belong to the category of2-bornanol, a derivative ofbornane. Some sources such as PubChem and CHEBI use the termborneol to refer to the entire category of 2-bornanols while others such as KEGG use the termborneol to refer to the compounds withendo hydroxyl only.
Borneol can be synthesized byreduction ofcamphor by theMeerwein–Ponndorf–Verley reduction (a reversible process). For flavoring purposes, a racemic mixture of camphor is used as starting material, leading to a racemic mixture of borneol andisoborneol. The chirality can be controlled by changing the chirality of camphor: (+)-camphor gives (−)-isoborneol and (+)-borneol.[7]
Borneol is synthesized usingDMAPP as the starting material. DMAPP is then converted toGPP, which is acted upon by abornyl diphosphate synthase to yield a bornyl diphosphate. A phosphatase then removes the phosphate groups, yielding borneol.[12]
The chirality of borneol in a plant depends on the preferred chirality of the bornyl diphosphate synthase. Synthases for either chirality have been sequenced.[12][13]
As mentioned above, both enantiomers of borneol occur in nature. Whereasd-borneol (+) was theenantiomer that used to be the most readily available commercially, the more commercially available enantiomer now isl-borneol (-).
Borneol generates aTRPM8-mediated cooling sensation similar to, but weaker than,menthol. It is more effective at activating TRPM8 at lower temperatures.[14]
Dextro-borneol (dexborneol) is used inedaravone/dexborneol, a drug approved in China for stroke. It is approved in intravenous (2021) and sublingual (2025) forms. The intravenous combination was approved on the basis of trials showing it to be superior to edavarone alone.[16][17]
Volume 1 of the modernChinese Pharmacopoeia, which deals with TCM and modernized TCM, lists uses for both enantiomers as well as the synthetic racemer.[11]
Borneol is widely used in ophthalmic preparations in China, though little is known about its exact function.[14]
Borneol may cause eye, skin, and respiratory irritation; it is harmful if swallowed.[18] Acute exposure may cause headache, nausea, vomiting, dizziness, lightheadedness, and syncope. Exposure to higher levels or over a longer period of time may cause restlessness, difficulty concentrating, irritability, and seizures.[19]
Borneol has been shown to have little to no irritation effect when applied to the human skin at doses used in fine fragrance formulation.[20] Skin exposure can lead to sensitization and a futureallergic reaction even to small quantities.[19]
The bornyl group is a univalent radical C10H17 derived from borneol by removal of hydroxyl and is also known as 2-bornyl.[21] Isobornyl is the univalent radical C10H17 that is derived from isoborneol.[22]Bornyl acetate is theacetateester of borneol.
Thenorborneols are derived from borneol and isoborneol by the removal of methyl groups, analogous to the change from bornane tonorbornane.
The epiborneols and isoepiborneols are analogously derived from epicamphor.[23]
^Lide, D. R., ed. (2005).CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton, Florida: CRC Press. p. 3.56.ISBN0-8493-0486-5.
^Gerhardt, C. (1842). "Sur la transformation de l'essence de valériane en camphre de Bornéo et en camphre des laurinées" [On the transformation of the essence of valerian into Borneo camphor and into laurel camphor].Comptes rendus.14: 832–835. From p. 834:"Je donne, par cette raison, à l'hydrogène carboné de l'essence de valériane, le nom debornéène, et, au camphre lui-même, celui debornéol." (I give, for this reason [namely, that the compound that Gerhardt had obtained from valerian oil was identical to that obtained by Pelouze from camphor from Borneo], to the hydrocarbon from valerian essence, the namebornéène, and, to camphor itself, that ofborneol.)
^Lincoln, D. E.; Lawrence, B. M. (1984). "The volatile constituents of camphorweed,Heterotheca subaxillaris".Phytochemistry.23 (4): 933–934.
^Begum, A.; Sandhya, S.; Shaffath Ali, S.; Vinod, K. R.; Reddy, S.; Banji, D. (2013). "An in-depth review on the medicinal floraRosmarinus officinalis (Lamiaceae)".Acta Scientiarum Polonorum: Technologia Alimentaria.12 (1):61–73.PMID24584866.
^Wong, K. C.; Ong, K. S.; Lim, C. L. (2006). "Composition of the essential oil of rhizomes ofKaempferia galanga L.".Flavour and Fragrance Journal.7 (5):263–266.doi:10.1002/ffj.2730070506.
^The Beaver: Its Life and Impact. Dietland Muller-Schwarze, 2003, page 43 (book at google books)
^Yang, Ming-Yeh; Khine, Aye Aye; Liu, Jen-Wei; Cheng, Hui-Chen; Hu, Anren; Chen, Hao-Ping; Shih, Tzenge-Lien (November 2018). "Resolution of isoborneol and its isomers by GC/MS to identify "synthetic" and "semi-synthetic" borneol products".Chirality.30 (11):1233–1239.doi:10.1002/chir.23017.PMID30222211.
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