Cembranoids from the cultured soft coral Sinularia sandensis

This study reports the isolation and characterization of two novel diterpenoids, norcembranoid 10-epi-dehydrogyrosanolide E (1) and cembranoid 8-epi-flexibilisolide G (2), from the cultured soft coral Sinularia sandensis. In addition to these new compounds, four known natural products were also identified: norcembranoid 10-epi-gyrosanolide E (3), cembranoid flexibilisolide G (4), and sesquiterpenoids sinularioperoxide A (5) and sinularioperoxide C (6). The chemical structures of the new marine natural products (1 and 2) were elucidated through extensive spectroscopic analysis, including 1D and 2D NMR, and by comparison with reported data. Notably, the new metabolites feature rare stereochemical variations within the cembranoid/norcembranoid framework, enriching structure-activity relationship insights for marine diterpenoids. Preliminary biological evaluation revealed that compound 1 exhibited cytotoxic activity against the MCF-7 human breast cancer cell line. Considering the recognized role of Sinularia-derived diterpenoids as promising anti-tumor scaffolds, these findings underscore the developmental potential of cultured soft corals as sustainable sources of structurally diverse and bioactive marine natural products.