Cytotoxic bastadin 24 from the Australian sponge Ianthella quadrangulata

A new cytotoxic bastadin, bastadin 24 (1), and the previously reported bastadins 4, 5, 6, 7, 12, 13, and 21 (2-8) were isolated from a polar extract of the Australian marine sponge Ianthella quadrangulata. The planar structure of bastadin 24 (1) was elucidated as the 25-hydroxy derivative of bastadin 6 (4) by employing spectroscopic techniques (NMR, MS, UV, and IR). All isolated bastadins were evaluated for their cytotoxicity toward a panel of 36 human tumor cell lines and were found to be moderately cytotoxic. Bastadin 24 (1) exhibited selective cytotoxic activity toward five of the 36 investigated tumor cell lines. Bastadins 7 (5) and 12 (6) significantly inhibited the serum + hEGF-induced (human epithelial growth factor) tubular formation of human umbilical vein endothelial cells (HUVEC) at a concentration of 1 mu g/mL.