Phytomedicine Plus (Feb 2022)
Centella asiatica: Secondary metabolites, biological activities and biomass sources
Abstract
Background: Phytochemistry of Centella asiatica (CA) gained momentum after the discovery of asiaticoside in the early 1940s. Though there is lot of literature on this precious herb, its chemistry has not been comprehensively reviewed. Moreover, several duplicate names, synonyms and contradictory findings were observed in CA literature. The traditional, food and vegetable, pharmaceutical and cosmetic uses of CA are steadily on the rise, resulting in its ever increasing biomass requirements. Methods: This article is an inclusive review of the last eight decades of chemistry of CA. Its biological activities, food and beverage, cosmetic applications and natural and alternate biomass sources are also assessed. CA literature for this review was gathered from web-based resources such as PubMed, Scopus and Google Scholar, and chemical structures were drawn using ChemDraw software. Results: So far 139 secondary metabolites were isolated from CA, viz., ursane-type triterpenes (11), oleanane-type triterpenes (5), ursane-type triterpene glycosides (30), oleanane-type triterpene glycosides (14), dammarane-type triterpene glycosides (15), steroids (4), steroid glycosides (2), flavonoids (18), polyacetylenes (9), phenolic acids (13) and other miscellaneous compounds (18). Of these 139 compounds, 70 are new entities described for the first time. Most prominent CA metabolites are the four ursane type triterpenes, viz., asiatic acid, madecassic acid, asiaticoside and madecassoside. Naming issues and contradictory findings are resolved in this article. Biological activities of CA and its secondary metabolites are also reviewed. The wide use of CA as a vegetable and food ingredient is justified by the antioxidant activities of its phenolics, flavonoids and other constituents. The traditional uses, geographical sources, conservation status, industrial demand, elite clones, alternative sources, chemical variability, ecological and other allied parameters and quality control requirements of CA are also discussed in the context of its chemistry and secondary metabolites. Conclusion: This review emphasizes the need to study the biology of the least investigated CA metabolites, viz., oleanane-type triterpenoids, caffeoyl quinic acids, polyacetylenes, phenolics, miscellaneous compounds. Moreover, a comprehensive description of the secondary metabolites in CA will aid its future chemistry, biosynthesis, chemical transformation and biological activity studies.
