Structures and cytotoxic activities of two new asterosaponins from the antarctic starfish Diplasterias brucei

Two new asterosaponins, diplasteriosides A and B, bearing the same β-D-Fucp-(1→2)-β-D-Galp-(1→4)-[β-D-Quip-(1→2)]-β-D-Quip-(1→3)-β-D-Quip-(1→ oligosaccharide chains linked to the C6 atom of the known genins, 3-O-sulfates of thornasterols A and B, respectively, were isolated from the Antarctic Diplasterias brucei starfish along with the previously known asteriidoside A. The structures of the new compounds were elucidated by two-dimensional NMR spectroscopy and mass spectrometry. Cytotoxicities of the isolated asterosaponins against the human colon cancer HCT-116, human breast cancer T-47D cell line, and human melanoma cancer RPMI-7951 cell lines were studied.