Antifouling activity of terpenoids from the corals Sinularia flexibilis and Muricella sp. against the bryozoan Bugula neritina.

Marine natural products are promising sources of green antifoulants. Here, a new compound (1) was isolated from the soft coral Sinularia flexibilis. This compound, another nine cembranoids (2-10) from S. flexibilis, and three eunicellin-type diterpenoids (11-13) from the gorgonian Muricella sp. were tested for antifouling activity against larval settlement of the bryozoan Bugula neritina. Compounds 2, 3, 4, 9, 12, and 13 exhibited significant antifouling activity, with EC50 values of 18.2, 99.7, 67.9, 35.6, 33.9, and 49.3 µM, respectively. Analysis of the structure-activity relationships suggested that the hydroxy group at C-13 in compound 4 reduced its antifouling activity.