Phomactins, novel PAF antagonists from marine fungus Phoma sp

PAF binding to receptors and PAF-induced platelet aggregation are inhibited by phomactin D, and phomactin B, B1, B2 and C antagonized PAF action at higher concentrations. All the phomactins are isolated from Phoma sp., a marine fungus. The binding activity is influenced by the conformation of the bicyclic ring system and its hydroxy group substitution pattern.