Scrobiculosides A and B from the deep-sea sponge Pachastrella scrobiculosa

Two new steroidal saponins, scrobiculosides A and B, were isolated from the deep-sea sponge Pachastrella scrobiculosa, collected at a depth of 200 m off Miura Peninsula, Japan. The aglycones of scrobiculosides A and B feature a vinylic cyclopropane and a increment (24,25) exomethylene on the side chains, respectively. Both saponins have a common sugar moiety composed of beta-d-galactopyranosyl-(1 -> 2)-6-acetyl-beta-d-glucopyranoside, with the exception of an acetyl group on C6 '' in scrobiculoside A. Scrobiculoside A exhibited cytotoxicity against HL-60 and P388 cells, with IC50 values of 52 and 61 mu M, respectively.