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In the present study, seven cembrane diterpenes were isolated from the soft coral Sinularia flexibilis by Toyopearl HW-40 column chromatography and High Performance Liquid Chromatography (HPLC). The diterpenes were identified as epoxycembrane A ( 1 ), sinularin ( 2 ), sinulariolide ( 3 ), (1 R ,13 S ,12 S ,9 S ,8 R ,5 S ,4 R )-9-acetoxy-5,8:12,13-diepoxycembr-15(17)-en-16,4-olide ( 4 ), 11-dehydrosinulariolide ( 5 ), (−)14-deoxycrassin ( 6 ) and dihydrosinularin ( 7 ). The antifouling activity of these compounds was examined by settlement assays, using the larvae of the bryozoan Bugula neritina and the barnacle Balanus albicostatus . With the exception of compound 2 , all compounds indicated significant antifouling activity and a variety of EC 50 values. In particular, compound 6 exhibited remarkable anti-settlement activity against the two biofoulers (EC 50 for B. neritina 3.90 μg ml −1 ; EC 50 for B. albicostatus 21.26 μg ml −1 ) as well as low toxicity against B. albicostatus larvae (LC 50 > 100 μg ml −1 ), suggesting its potential as an environmentally friendly antifoulant. This is the first report on the antifouling activity of compounds 1 and 4 – 7 , further demonstrating the involvement of cembrane diterpenes in the chemical defense of soft corals against surface fouling. [ABSTRACT FROM AUTHOR]

Two new cembrane diterpenes (+)-polydactylide ( 1 ) and (+)-7α,8β-dihydroxydeepoxysarcophine ( 2 ) together with (+)-sarcophine ( 3 ) and (+)-sarcophytoxide ( 4 ) have been isolated from the soft coral Sinularia polydactyla . The new cembrane diterpene (-)-7β-hydroxy-8α-methoxydeepoxysarcophine ( 5 ) has been obtained from the soft coral Sarcophyton trocheliophorum and the known briarane diterpene briaexcavatolide W ( 6 ) from the gorgonian coral Briareum sp. The structures were determined primarily by NMR spectroscopy. The assignment of NMR signals was performed by means of 1 H– 1 H COSY, ROESY, HMQC and HMBC experiments. [ABSTRACT FROM AUTHOR]