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 alpha-methylene-gamma-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.