Imidazole alkaloids from the indopacific sponge Pericharax heteroraphis

Chemical investigation of the sponge Pericharax heteroraphis (Polejeff) collected in Indonesia, has led to the isolation of three imidazole alkaloids, preclathridine-A (1), leucettamine-B (2) and leucettamine-A (3). The structures of the isolated compounds were unambiguously established by D-1 and D-2 NMR and mass data. This is the first report of this class of compounds from the P. heteroraphis sponge. Investigation of the antimicrobial activities of the isolated compounds showed that leucettamin-A (3) was active against the gram-positive bacteria Staphylococcus aureus and the fungus Cladosporium herbarum, while other compounds were inactive.