Chemical structures, production and enzymatic transformations of sapogenins and saponins from Centella asiatica (L.) Urban.

Centella asiatica (L.) Urban is a medicinal herb traditionally used in Asiatic countries for its multiple therapeutic properties, essentially due to its accumulation of specific pentacylic triterpenoid saponins, mainly asiaticoside and madecassoside and the corresponding sapogenins. This review summarizes the updated knowledge about the chemical structures of about forty centelloids, found as minor metabolites in Centella, and all derived from ursane and oleane ring patterns. Similarly, the most recent genetic and enzymatic features involved in their biosynthesis is reviewed, in relation with their biotechnological production developed, either from in vitro plant cultures or undifferentiated cells, in order to be independent of natural sources and to provide a continuous and reliable source of centelloids. Finally, a short survey of the biotransformations of some centelloids, either in animal, human or microorganisms is reviewed.