Four new ent-kaurene diterpene glucosides from Mikania micrantha

Abstract Phytochemical study on the aerial parts of Mikania micrantha led to the isolation of four new ent -kaurene diterpene glucosides, β- d -glucopyranosyl-15α-(3-hydroxy-3-methylbutanoyloxy)-9β-hydroxy- ent -16-kauren-19-oate ( 1 ), β- d -glucopyranosyl-15α-(3-methylbutanoyloxy)-9β-hydroxy- ent -16-kauren-19-oate ( 2 ), β- d -glucopyranosyl-15α-(2-methylbutanoyloxy)-9β-hydroxy- ent -16-kauren-19-oate ( 3 ), β- d -glucopyranosyl-15α-(3-methyl-2-butenoyloxy)-9β-hydroxy- ent -16-kauren-19-oate ( 4 ), along with a known one, β- d -glucopyranosyl-15α-(3-hydroxy-3-methylbutanoyloxy)- ent -16-kauren-19-oate ( 5 ). Their structures were elucidated on the basis of extensive spectroscopic analysis. Compounds 1 – 4 are a group of C-9 hydroxylated ent -kaurene diterpene glucosides which is relatively rare in nature. These compounds were tested for their in vitro antibacterial activity against four assayed Gram-(+) and three Gram-(−) bacteria, while the results were poor. In addition, the in vitro growth inhibitory activity of these compounds against human cancer cell lines Hela, A549, HepG-2 and MCF-7, were also tested.