117(P-70) Chondrosiamide A, B, and C, Three Novel Cytotoxic Cyclic Depsipeptides from a Marine Sponge, Chondrosia chucalla
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Marine sponges have proved to be a rich source of secondary metabolites with unusual structures as well as interesting biological activities. In the course of our continuing research on biologically active compounds from Japanese marine invertebrates, we have investigated the isolation for the cytotoxic principle from the marine sponge Chondrosia chucalla. We report here the isolation and structure elucidation of three novel cyclic depsipeptides, chondrosiamide A (1), B (2), and C (3). C. chucalla was collected by hand at depths of 10m off Hedo Point, Okinawa, Japan, in July 2000. The diethyl ether-soluble fraction of the EtOH extract showed cytotoxcity against KB cells. Bioassay guided the separation of the active fraction by Sephadex LH-20, silica gel chromatography, reversed-phase HPLC to give three active compounds, 1 (16.8mg), 2 (26.7mg), and 3 (3.9mg). The structure of chondrosiamides was determined on the basis of spectral and chemical methods. Absolute configuration of amino acid residues was determined by Marfey's analysis. Chondrosiamide A (1) and B (2) showed cytotoxicity against KB cells at the IC_<50> value of 9.7 and 2.8μM, respectively.
