New dolabellanes from the Taiwanese soft coral Clavularia inflata

Bioassay-directed fractionation of the acetone extract of Clavularia inflata collected in Green Island has afforded two new dolabellane diterpenoids, designated as clavinflols A (4) and B (5) in addition to the reported (1R*, 12R*)-dolabella-4(16),7,10-triene-3,13-dione (1), stolonidiol (2) and stolonidiol monoacetate (3). The structures of compounds 4 and 5 were determined on the basis of 1D and 2D-NMR techniques including COSY, HSQC, HMBC and NOESY experiments, and acetylation which yielded derivatives 6 and 7, respectively. Pharmacological study revealed that compounds 1-3 and 5 exhibited cytotoxicity against human oral epidermoid carcinoma (KB) cells while compound 4 showed selective activity toward human Hepa cells.