Cytotoxic and Antibacterial Cembranoids from a South China Sea Soft Coral, Lobophytum sp.

Chemical examination of a South China Sea soft coral Lobophytum sp. led to the isolation of three new α-methylene-γ-lactone-containing cembranoids, (1R*,3R*, 4R*,14R*,7E,11E)-3,4-epoxycembra-7,11,15(17)-trien-16,14-olide (1), (1R*,7S*,14S*,3E, 11E)-7-hydroperoxycembra-3,8(19),11,15(17)-tetraen-16,14-olide (2), and (1R*,7S*,14S*, 3E,11E)-18-acetoxy-7-hydroperoxycembra-3,8(19),11,15(17)-tetraen-16,14-olide (3), along with eleven known analogues 4–14. The structures of the new compounds were elucidated through extensive spectroscopic analysis, including 1D and 2D NMR data. Compounds 1–3 exhibited moderate cytotoxic activity against the selected tumor cell lines. Moreover, 2 and 3 were found to be moderate inhibitors against the bacteria S. aureus and S. pneumoniae