Antiproliferative diterpenoids from the leaves of Isodon rubescens.

A phytochemical study of Isodon rubescens leaves led to the isolation of five new diterpenoids, isorubesins A-E ( 1- 5), and fifteen known diterpenoids. The structures of these new compounds were elucidated by spectroscopic evidence. Most of the diterpenoids were tested for cytotoxicity against NB4, A549, SHSY5Y, PC3, and MCF7 human tumor cells. Some of them showed potent inhibitory activity. Compound 5 is the first reported atisane-type diterpenoid from this plant.