Calamenenes - aromatic bicyclic sesquiterpenes - from the Indian gorgonian Subergorgia reticulata (Ellis and Solander, 1786)

Three aromatic sesquiterpene derivatives, (+)-(7R, 10S)-2-methoxy calamenene (1), (+)-(7R, 10S)-2,5-dimethoxy calamenene (2) and (+)-(7R, 10S)-2-methoxy-5-acetoxy calamenene (3) were isolated from the methanol extract of the Indian gorgonian Subergorgia reticulata. Compound 2 has not been previously described in the literature. Compound 3 has not been isolated previously from a natural source. Compounds 1, 2 and 3 showed settlement inhibition activity against cyprids of Balanus amphitrite with EC50 values of 4.4, 7.8 and 0.03 mu g mL-1, respectively. These compounds also exhibited considerable activity against Artemia nauplii at 50 mu g mL-1, indicative of their potential use as cytotoxic agents.