ABSTRACT
Like all terpenoid compounds, triterpenes are composed of isoprene units. Via farnesyl-diphosphate, six of them form squalene, an acyclic intermediate that is synthesized in all living organisms. From this compound, two biosynthesis pathways originate. Through epoxidation, cyclization, and conformational changes, one leads to the formation of cycloartenol and cholesterol (which is the precursor of steroids, steroid alkaloids, and cardenolides), and the other one to triterpenes. The latter are a large group of natural compounds, with ~1700 derivatives known thus far. They share the same number of carbons in their scaffold (30), and depending on the number of rings they can be separated in tetra-and pentacyclic derivatives [1-3]. Examples for the ‚rst group are dammaranes and lanostanes; they both derive from gonane, the steroid nucleus. Oleananes, ursanes, and lupanes are pentacyclic triterpenes (Figure 42.1).
