A NEW MERODITERPENOID DIMER FROM AN UNDESCRIBED PHILIPPINE MARINE SPONGE OF THE GENUS STRONGYLOPHORA

An undescribed Philippine marine sponge of the genus Strongylophora yi elded a new meroditerpenoid-strongylophorine dimer (1) and the known m eroditerpenoids, strongylophorine-2 (2), strongylophorine-3 (3), and s trongylophorine-4 (4). The structures of the compounds were establishe d on the basis of NMR spectroscopic and mass spectrometric data. The p osition of the inter-unit linkage in the new compound was elucidated a fter methylation and 1D H-1 NOE difference experiments. This is the fi rst report wherein the H-1 and C-13 NMR data of the strongylophorine c ongeners are fully and unambiguously assigned on the basis of 2D NMR s pectroscopy. Compounds 2 and 3 exhibited slight activity against Micro coccus luteus and Salmonella typhii, respectively. Compound 3 was acti ve against the phytopathogenic fungus Cladosporium cucumerinum and als o against the neonate larvae of the polyphagous pest insect Spodoptera littoralis (EC50 of 69 [+/-0.48 (S.E.)] ppm) when incorporated into a rtificial diet. Compound 1 was found to be the most active in the brin e shrimp lethality test with a LC50 of 10.5 [+/-0.43 (S.E.)] mu g/mL.