Cytotoxic ent-kaurane diterpenoids from Isodon henryi.

Five new ent-kaurane diterpenoids, isodonhenrins A-E (1-5), together with thirteen known ones were isolated from the aerial parts of Isodon henryi. Their structures were identified by means of extensive spectroscopic analysis, and the absolute configurations of 1 were determined by single-crystal X-ray diffraction. Most of the diterpenoids were evaluated for their cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cell lines. Compound 17 showed significant inhibitory effects on five cell lines, and compounds 6, 9, 10, 11, 12 and 16 exhibited selective activity.