A new rearranged abietane diterpenoid from Clerodendrum kaichianum Hsu.

A new abietane diterpenoid, (3S,16R)-12,16-epoxy-3,6,11,14,17-pentahydroxy-17(15 â†’ 16)-abeo-5,8,11,13-abietatetraen-7-one (1), was isolated from the stems of Clerodendrum kaichianum Hsu, together with four known diterpenoids. The structures of the isolated compounds were assigned on the basis of their NMR spectra including 2D NMR techniques such as COSY, HMQC, and HMBC experiments, and were compared with those of the literature data. This new compound showed significant cytotoxicity against the HL-60 and A-549 tumor cell lines.