Cytotoxic ent-kaurane diterpenoids from Isodon nervosus.

Four new ent-kaurane diterpenoids, rabdonervosins G-J (1-4, resp.), were isolated from the leaves and stems of Isodon nervosus. Their structures were elucidated by extensive spectroscopic analyses, including 1D-, 2D-NMR and HR mass spectra. Compound 2 showed potent cytotoxicity against the HepG2 and PC-9/ZD cell lines with IC50 values of 2.36 and 6.07 µM, respectively, and compound 3 exhibited cytotoxicity against the HepG2 and CNE2 cell lines with IC50 values of 8.64 and 9.77 µM, respectively.