Suberosanones A-C, New Metabolites Possessing Cyclopentenone System from the South China Sea Gorgonian Coral Subergorgia suberosa

Two unusual novel bicyclic lactones, suberosanones A and B (1 and 2, resp.), characterized by the co-occurrence of cyclopentenone and butanolide rings within the same molecule, along with one tricyclic cyclopentenone derivative, suberosanone C (3), were isolated from the South China Sea gorgonian coral Subergorgia suberosa. Their structures were unambiguously established by detailed spectroscopic analyses (NMR, IR, and HR-MS). The absolute configurations of 1 and 2 were determined by quantum-chemical calculations using the time-dependent density-functional theory (TDDFT) method. All compounds showed neither antifouling activity against Balanus amphitrite larvae settlement nor antibacterial activity against a panel of bacterial strains at concentrations up to 25 mu g/ml.