Recently Isolated Bioactive Compounds from Korean Marine Sponges

Marine sponges are recognized as a plentiful source of diverse biologically active secondary metabolites. Recently, we have initiated a research to discover antitumor constituents from the marine sponges collected from Korean Waters. Marine sponges collected from the South Sea of Korea were screened for several biological activities including such as brine shrimp lethality and cytotoxicity. Significant brine shrimp lethality was detected in the crude extract of a two-sponge association of Poecillastra sp. and Jaspis sp. A cross-section of this sample showed two layers of morphologically distinct sponges. The thin and dirty yellow outer layer was identified as Poecillastra sp. (Pachastrellidae), the surface of which was very rough. The light-grey inner layer was identified as Jaspis sp. (Jaspidae), the surface of which was smooth. This two-sponge association appears to be consistent as these sponges were always found in associated form regardless of collection site or collection period. Investigation of the bioactive constituents monitored by brine shrimp lethality assay led to the isolation of pectenotoxin II (PTX2) and psammaplin A as causative compounds for the brine shrimp lethality. $^1$H- and $\^$13/C-nmr signals of PTX2 was fully assigned utilizing TOCSY, HETCOR, Long-range HETCOR, and Homonuclear J-resolved 2D experiments. PTX2 displayed very potent and selective cytotoxicities in the 60 cell line panel antitumor assay at the NCI. PTX2 has progressed to acute toxicity determination and in vivo antitumor assay at the NCI (Table 1). However, significant in vitro antitumor activity of PTX2 can not be affirmed in the in vivo assay.