Cytotoxic diterpenoids from Isodon enanderianus.

Five new ent-kaurane diterpenoids, enanderianins K-O (1-5), and one new ent-abietane diterpenoid, enanderianin P (6), together with five known ent-kaurane diterpenoids, rabdocoetsin A (7), rabdocoetsin B (8), rabdocoetsin D (9), megathyrin A (10), megathyrin B (11) were isolated from the aerial parts of Isodon enanderianus. Their structures were determined by spectral means. Some diterpenoids were tested for their cytotoxicity against the human tumor K562 cells. Compounds 1, 2, 6, 8, 9 showed significant inhibitory activities against K562 cells with IC50 values ranging from 0.13 to 0.87 microg/mL.