Antifouling Substances from a Palauan Octocoral Sinularia sp

During the course of our search for naturally occurring antifouling substances from marine invertebrates, we found that acetone extract of an octocoral Sinularia sp. collected in Palau 1991 showed potent activity against the blue mussel Mytilus edulis L. Bioassay guided isolation determined 13 alpha -acetoxypukalide (1) and (9E)-4-(6,10-dimethylocta-9,11-dienyl)furan-2-carboxylic acid (2) to be the active substances. They were also tested against cyprid larvae of the barnacle Balanus amphitrite. Though 1 showed weak activity against the blue mussel, it completely inhibited larval settlement at 0.1 ppm. This activity was higher than that of CuSO sub(4) and TBTO (bistributyltin oxide, one of the most effective antifoulants). Compound 2 showed 74% activity of CuSO sub(4) at 0.2 mg/cm super(2) against the blue mussel.