Sesquiterpenes are a class ofterpenes that consist of threeisoprene units and often have themolecular formula C15H24. Likemonoterpenes, sesquiterpenes may be cyclic or contain rings, including many combinations. Biochemical modifications such asoxidation orrearrangement produce the related sesquiterpenoids.[1] It is estimated (2006) that 3000 sesquiterpenes have been identified.[2]
Farnesyl pyrophosphate, precursor to all sesquiterpenes
Cyclic sesquiterpenes are more common than cyclic monoterpenes because of the increased chain length and additional double bond in the sesquiterpene precursors. In addition to common six-membered ring systems such as the ones found inzingiberene andbisacurone, cyclization of one end of the chain to the other end can lead to macrocyclic rings such ashumulene.
Caryophyllene, which is pervasive but especially in cloves.
Thecadinenes contain two fused six-membered rings.Caryophyllene, a component of manyessential oils such as clove oil, contains a nine-membered ring fused to acyclobutane ring. Rishitin is another example of a cadinene, which is found in potatoes and tomatoes.[6][7]
The FPP backbone can be rearranged in several different ways and further decorated with different functional groups, hence the large variety of sesquiterpenoids.Geosmin, the volatile compound that gives an earthy taste and musty odor in drinking water and the characteristic odor on a rainy day, is a sesquiterpenoid, produced by bacteria, especiallycyanobacteria, that are present in the soils and water supplies.[8] Oxidation of farnesene then provides the sesquiterpenoidfarnesol.
Sesquiterpene lactones are a common class of sesquiterpenoids that contain alactone ring, hence the name. They are found in many plants and can cause allergic reactions and toxicity if consumed excessively, particularly in grazing livestock.[9]
The term merosesquiterpenoids was coined in 1968 to describe molecules of this class that have a mixed biosynthetic origin, meaning isoprenoid precursors like isopentenyl pyrophosphate are derived from both themevalonate andnon-mevalonate pathways.[10]
^Davis, Edward M.; Croteau, Rodney (2000). "Cyclization Enzymes in the Biosynthesis of Monoterpenes, Sesquiterpenes, and Diterpenes".Topics in Current Chemistry.209:53–95.doi:10.1007/3-540-48146-X_2.ISBN978-3-540-66573-1.
^Katsui, N.; Murai, A.; Takasugi, M.; Imaizumi, K.; Masamune, T.; Tomiyama, K. (1968). "The structure of rishitin, a new antifungal compound from diseased potato tubers".Chemical Communications (1):43–44.doi:10.1039/C19680000043.
^D’Harlingue, A., Mamdouh, A. M., Malfatti, P., Soulie, M.-C., & Bompeix, G. (1995). Evidence for rishitin biosynthesis in tomato cultures. Phytochemistry, 39(1), 69–70.https://doi.org/10.1016/0031-9422(94)00844-J
^Izaguirre G, Taylor WD (June 1995). "Geosmin and 2-methylisoborneol production in a major aqueduct system".Water Science and Technology.31 (11):41–48.doi:10.1016/0273-1223(95)00454-u.
![Humulene, found in hops.[5]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aHumulene.png)
