| Research Abstract |
Marine organisms comprise over half a million species. Due to their unusual living environment as compared with terrestrial organisms, marine organisms metabolite and produce a variety of substances which often have various unprecedented chemical structures and biological activities. During the course of continuing studies in search of new biologically active substances from marine organisms, we have studied several marine sponges collected in the coral reef of Okinawa Prefecture and Palau Islands.
1. Bioactive five lactones named theonellapeptolides Ia, Ib, Ic, Id, and Ie were isolated from the Okinawan marine sponge Theonella swinhoei and elucidated their absolute stereostructures by a new HPLC method for N-methly amino acids which was developed to analyze the amino acid composition of these peptide lactones. These peptide lactones are cytotoxic for L1210 cell and exhibit ionophoric activities to Na^+, K^+, and Ca^<++>
2. Nine new norlanostane-triterpenoid oligoglycosides, sarasinosides A_1, A_2, A_3, B_1, B_2, B_3, C_1 C_2, and C_3 were isolated from the Palauan marine sponge Asteropus sarasinosum and their structures were determined. These oligoglycosides exhibit ichthyotoxic activity and inhibit cell division of fertilized eggs ofthe starfish.
3. Nine novel macrocyclic alkaloids, araguspongines A-H, and J were isolated from an Okinawan marine sponge Xestospongia sp. and their absolute stereostructures were determined. These alkaloids having two l-oxaquinolizidine moieties exhibit potent vasodilative activity.
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