New oxygenated sesquiterpenes from the Indonesian soft coral Nephthea chabrolii

The Indonesian soft coral Nephthea chabrolii afforded two new oxygenated sesquiterpenes: hydroxycolorenone (1) and methoxycolorenone (2), as well as the known liverwort metabolite (+)-cyclocolorenone (3). This is the first report of the occurrence of such terrestrial liverwort metabolites in marine soft corals. The structures of the new compounds were unambiguously established an the basis of NMR spectroscopic data (H-1, C-13, COSY, H-1-defected direct and long-range C-13-H-1 correlations). Compound 1 exhibited insecticidal activity towards neonate larvae of the polyphagous pest insect Spodoptera littoralis, with an EC50 of 8.8 ppm and a LC50 of 453 ppm, when incorporated in artificial diet and offered to larvae in a chronic feeding bioassay.