Anti-biofouling marine diterpenoids from Okinawan soft corals

Soft corals produce a diverse range of natural products with pharmaceutical potential, such as antiproliferative and anti-inflammatory effects. The Alcyoniidae family, particularly the genera Sarcophyton and Sinularia, is rich in bioactive terpenoids. However, despite extensive research, their anti-biofouling properties against the mussel Mytilus galloprovincialis remain underexplored. This study investigates these compounds as potential eco-friendly antifouling agents. A new cembrane-type diterpenoid, 11,12-epoxycembrene A (1), and 15 known compounds were isolated from three soft corals distributed in Okinawa, Japan. The chemical structures of these secondary metabolites were elucidated based on spectroscopic analysis. Moreover, an anti-biofouling assay of potential anti-biofouling agents against M. galloprovincialis was performed and their toxicities were assessed by means of the brine shrimp mortality test. In conclusion, this study identifies new and known bioactive compounds from soft corals, introduces an improved anti-biofouling assay, and highlights the potential of dimethylamine-containing diterpenes as environmentally friendly antifouling agents.