Notes on the occurrence and significance of triterpenoids (asiaticoside and related compounds) and caffeoylquinic acids in Centella species

Asiaticoside, a well-known ursane-type triterpene saponin widely used as a chemical marker in quality control of commercial samples of Centella asiatica, occurs in South African material (12 samples from four provenances) at a level of 1 to 2% of dry weight. Surprisingly, the compound was not detected in three samples of C. glabrata, the only other species with a well-recorded history of medicinal use. A preliminary LC-MS survey of a further 21 leaf samples from 16 species of Centella revealed the presence of asiaticoside as a major constituent in ten of the species studied, while others had various isomers of chlorogenic and dicaffeoylquinic acids. Multiple samples from the same species were chemically similar, indicating that a wider chemosystematic study of the entire genus may yield valuable results. The study also showed that South African genotypes of C. asiatica may be suitable for commercial use and that several other Centella species are potential sources of asiaticoside.