New clerodane diterpenoids from the roots of Polyalthia laui

Five new clerodane diterpenoids, polylauiester A (1), (4→2)-abeo-2,13-diformyl-cleroda-2,12E-dien-14-oic acid (2) and polylauiamides B-D (3-5), together with 11 known clerodane diterpenoids (6-16), were isolated from the roots of Polyalthia laui. Among them, polylauiester A (1) represents the first example of a novel norclerodane diterpenoid only containing 17 carbon atoms on the carbon skeleton, and polylauiamide B (3) is an unusual diterpenoid with a p-substituted benzene ring as a substituent. Their structures were elucidated by extensive spectroscopic methods, and the relative configuration of polylauiamide B (3) was further confirmed by the single crystal X-ray diffraction method. Biological evaluation of new compounds against human Hela, MCF-7 and A549 human cancer cell lines showed that all compounds displayed weak cytotoxicities against various human cancer cell lines in the range of IC50 at 25.01-39.31μM.