Antifouling metabolites from the mangrove plant Ceriops tagal

The new diterpene methoxy-ent-8(14)-pimarenely-15-one (1) and three known metabolites: ent-8(14)-pimarene-15R,16-diol (2), stigmasterol (3) and beta-sitosterol (4), were isolated from the roots of the mangrove plant Ceriops tagal. Their structures and relative stereochemistry were elucidated by means of extensive NMR, IR and MS analysis. Compounds 1, 2, 3 and 4 exhibited significant antifouling activities against cyprid larvae of the barnacle Balanus albicostatus Pilsbry, with EC(50) values of 0.32 +/- 0.01, 0.04 +/- 0.00,4.05 +/- 0.15 and 18.47 +/- 0.40 microg/cm(2), respectively, whereas their toxicities towards cyprids were very low, with LC(50 )values all above 10 microg/cm(2).