Norlanostane triterpenoidal saponins from the marine sponge Melophlus sarassinorum

Along with five known 30-norlanostane-type saponins, sarasinosides A(1) (5A), A(3) (6A), h (7), 12 (8), and H-2 (9), four new triterpenoidal saponin congeners, sarasinosides J (1), K (2), L (3), and M (4), were isolated from the Indonesian sponge Melophlus sarassinorum. Sarasinosides J (1) and K (2) are the 24,25-hydrogenated congeners of the previously described sarasinosides A(1) and H-2, respectively. The carbon skeleton of sarasinoside M (4) possesses a rearranged 8 alpha,9 alpha-epoxy-8,9-seconorlanosta-8(14),9(11),24-triene system, which is novel and unprecedented in nature. The structures of the new compounds were confirmed by spectral analyses, chemical derivatization, and GC analyses. Compounds 1 and 5A exhibited antimicrobial activity toward Bacillus subtilis and Saccharomyces cerevisiae.