Triterpenes are a class of chemical compounds composed of three

terpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ...

units with the molecular formula C₃₀H₄₈; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi all produce triterpenes, including

squalene Squalene is an organic compound. It is a triterpenoid with the formula C30H50. It is a colourless oil, although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as ''Squalus'' is a genus of sharks). A ...

, the precursor to all steroids.

Structures

Triterpenes exist in a great variety of structures. Nearly 200 different skeletons have been identified. These skeletons may be broadly divided according to the number of rings present. In general pentacyclic structures (5 rings) tend to dominate.

Squalene Squalene is an organic compound. It is a triterpenoid with the formula C30H50. It is a colourless oil, although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as ''Squalus'' is a genus of sharks). A ...

is biosynthesized through the head-to-head condensation of two farnesyl pyrophosphate units. This coupling converts a pair of C15 components into a C30 product. Squalene serves as precursor for the formation of many triterpenoids, including bacterial

hopanoids Hopanoids are a diverse subclass of triterpenoids with the same hydrocarbon skeleton as the compound hopane. This group of pentacyclic molecules therefore refers to simple hopenes, hopanols and hopanes, but also to extensively functionalized deri ...

and eukaryotic sterols.

Triterpenoids

By definition triterpenoids are triterpenes that possess

heteroatom In chemistry, a heteroatom () is, strictly, any atom that is not carbon or hydrogen. Organic chemistry In practice, the term is usually used more specifically to indicate that non-carbon atoms have replaced carbon in the backbone of the molecula ...

s, usually oxygen. The terms ''triterpene'' and ''triterpenoid'' often are used interchangeably. Triterpenoids possess a rich chemistry and pharmacology (e.g.

cholesterol Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...

) with several pentacyclic motifs. Lupane,

oleanane Oleanane is a natural triterpenoid. It is commonly found in woody angiosperms and as a result is often used as an indicator of these plants in the fossil record. It is a member of the oleanoid series, which consists of pentacyclic triterpenoids ( ...

and ursane show particular promise as anti-cancer agents.

Steroids

Steroids feature a

cucurbitane Cucurbitane is a class of chemical compounds with formula ( CAS number 65441-59-0). It is a polycyclic hydrocarbon, specifically triterpene. It is also an isomer of lanostane (specifically 19(10→9β)-abeolanostane), from which it differs by ...

core, although in practice they are biosynthesised from either

lanosterol Lanosterol is a tetracyclic triterpenoid and is the compound from which all animal and fungal steroids are derived. By contrast plant steroids are produced via cycloartenol. Role in biosynthesis of other steroids Elaboration of lanosterol under en ...

(animals and fungi) or cycloartenol (plants) via the cyclization of

. Steroids have two principal biological functions, being either key components of cell membranes or signaling molecules that activate steroid hormone receptors. Important sub-classes include sterols and

cucurbitacin Cucurbitacin is a class of biochemical compounds that some plants – notably members of the pumpkin and gourd family, Cucurbitaceae – produce and which function as a defence against herbivores. Cucurbitacins are chemically classified as t ...

Triterpenoid saponins

Triterpenoid saponin Saponins (Latin "sapon", soap + "-in", one of), also selectively referred to as triterpene glycosides, are bitter-tasting usually toxic plant-derived organic chemicals that have a foamy quality when agitated in water. They are widely distributed ...

s are triterpenes which belong to the saponin group of compounds, making them triterpenoid

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycoside ...

s. They are produced by plants as part of their self-defense mechanism with important sub-classes including

ginsenoside Ginsenosides or panaxosides are a class of natural product steroid glycosides and triterpene saponins. Compounds in this family are found almost exclusively in the plant genus '' Panax'' (ginseng), which has a long history of use in traditional m ...

s and

eleutheroside Eleutherosides are a diverse group of chemical compounds that were isolated from roots of the herb ''Eleutherococcus senticosus'' which is commercially offered mostly as extracts. Eleutheroside A is a saponin and sterol glycoside while other eleuth ...

References

{{Terpenoids *