sesquiterpene

thumb|right|Big Sagebrush ([[Artemisia tridentata) contains sesquiterpene lactones which are sesquiterpenoids (built from three isoprene units) and contain a lactone ring, hence the name. These compounds are found in many other plants and can cause allergic reactions and toxicity if consumed in excess, particularly in grazing livestock.]] thumb|Phallus indusiatus, in [[Cooktown, Queensland, Australia, which produces two unique sesquiterpenes]] Sesquiterpenes are a class of terpenes that consist of three isoprene units and often have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be cyclic or contain rings, including many combinations. Biochemical modifications such as oxidation or rearrangement produce the related sesquiterpenoids. It is estimated (2006) that 3000 sesquiterpenes have been identified.

==Biosynthesis and examples== The reaction of geranyl pyrophosphate with isopentenyl pyrophosphate results in the 15-carbon farnesyl pyrophosphate (FPP), which is an intermediate in the biosynthesis of sesquiterpenes such as farnesene. thumb|300px|none|Farnesyl pyrophosphate, precursor to all sesquiterpenes