Triterpene

Triterpenes are a large and diverse class of natural products composed of six isoprene units, totaling about C30 in most structures. They arise primarily in plants and fungi as secondary metabolites, though some marine organisms also produce triterpenoids. Biosynthetically, two molecules of farnesyl pyrophosphate form squalene, which is then converted to oxidosqualene and cyclized by oxidosqualene cyclases to generate a variety of core skeletons. These cores include sterol frameworks such as cycloartenol in plants and lanosterol in many other organisms, as well as pentacyclic structures of oleanane, ursane, lupane, and dammarane types. Subsequent oxidations, rearrangements, and glycosylations expand this diversity, yielding aglycones and glycosides known as triterpenoids and triterpene saponins.

Structural diversity in triterpenes underpins a wide range of biological roles. Sterols function as membrane components and precursors to key hormones, while many non-sterol triterpenoids act as defense compounds against pathogens and herbivores. Plant triterpenes are widespread in leaves, fruits, roots, and bark; fungi commonly produce lanostane-type derivatives; marine organisms contribute unique backbones as well.

Significance and applications vary with structure. Some triterpenoids exhibit pharmacological activities, including anti-inflammatory, antiviral, and anticancer effects; notable examples are betulinic acid, oleanolic acid, and ursolic acid. Triterpene saponins possess surfactant-like properties and are used in cosmetics, nutraceuticals, and as natural emulsifiers.