Bioactive Diterpenoids Isolated from Dilophus ligulatus.

Nine diterpenoids, acetyldictyolal ( 1), epoxyoxodolabelladiene ( 2), dictyotalide B ( 3), neodictyolactono ( 4), pachylactone ( 5), the acetals 6A and 6B, isoacetoxycrenulatin ( 7), and dictyolactone ( 8) were isolated from the brown alga DILOPHUS LIGULATUS (Kütz.) Feldm. Their structures have been elucidated by comparison of mass, IR, (1)H- and (13)C-NMR spectra with reported literature data. Compounds 1, 2, 4, 7, and 8 exhibited antifungal activity. Cytotoxic activity against several types of mammalian cells (KB, P-388, P-388/DOX, and NSCLCN6-L16) in culture was examined for the 8 diterpenoids. Some of them showed stronger cyto-toxicity than mercaptopurine which was used as a positive control in this study.