Cycloartenol

Cycloartenol is a sterol found in plants and some algae. It is the first cyclization product of the isoprenoid precursor 2,3-oxidosqualene in the plant sterol biosynthesis pathway, formed by the enzyme cycloartenol synthase. Cycloartenol has a tetracyclic triterpene skeleton with a distinctive cyclopropane-containing ring system and a 3β-hydroxyl group, classifying it as a C30 sterol.

As a key biosynthetic intermediate, cycloartenol is converted through a series of oxidation, demethylation, and rearrangement reactions to yield the phytosterols that accumulate in plant membranes, such as campesterol, stigmasterol, and sitosterol. The pathway from cycloartenol to these end products involves multiple enzymatic steps, including 4-demethylation and side-chain modifications, and parallels the animal pathway that uses lanosterol as a starting point.

Occurrence and function: Cycloartenol is widely distributed in higher plants and some algae. In plants, it serves as the principal entry point into the sterol biosynthetic pathway and is ultimately incorporated into membrane lipids and other sterol-containing metabolites. While it is not a major dietary component in animals, the phytosterols derived from this pathway play roles in membrane structure and physiology.

Applications and significance: In geochemistry, cycloartenol and related cycloartane sterols are used as biomarkers to indicate input from green plants and terrestrial vegetation in sedimentary records. Their presence helps researchers reconstruct past vegetation and environmental conditions.