Cytotoxic Steroidal Saponins from the Rhizomes of Tacca integrifolia

Abstract

Three new steroid saponins (3beta ,25R)-spirost-5-en-3-yl 6-deoxy-alpha -L-mannopyranosyl-(1->2)-[beta -D-glucopyranosyl-(1->4)-6-deoxy-alpha -L-mannopyranosyl-(1->3)]-beta -D-glucopyranoside (1), (3beta ,22R,25R)-26-(beta -D-Glucopyranosyloxy)-22-hydroxyfurost-5-en-3-yl 6-deoxy-alpha -L-mannopyranosyl-(1->2)-[6-deoxy-alpha -L-mannopyranosyl-(1->3)]-beta -D-glucopyranoside (3), and (3beta ,22R,25R)-26-(beta -D-glucopyranosyloxy)-22-hydroxyfurost-5-en-3-yl 6-deoxy-alpha -L-mannopyranosyl-(1.-+.2)-[beta -D-glucopyranosyl-(1->4)-6-deoxy-alpha -L-mannopyranosyl-(1->3)]-beta -D-glucopyranoside (5), as well as the new pregnane glycoside (3beta ,16beta )-3--20-oxopregn-5-en-16-yl (4R)-5-(beta -D-glucopyranosyloxy)-4-methylpentanoate (6), were isolated from the rhizomes of Tacca integrifolia together with two known (25R) configurated steroid saponins (3beta ,25R)-spirost-5-en-3-yl 6-deoxy-alpha -L-mannopyranosyl-(1->2)-[6-deoxy-alpha -L-mannopyranosyl-(1->3)]-beta -D-glucopyranoside (2) and (3beta ,22R,25R)-26-(beta -D-glucopyranosyloxy)-22-methoxyfurost-5-en-3-yl 6-deoxy-alpha -L-mannopyranosyl-(1->2)-[6-deoxy-alpha -L-mannopyranosyl-(1->3)]-beta -D-glucopyranoside (4). The cytotoxic activity of the isolated compds. was evaluated in HeLa cells and showed the highest cytotoxicity value for compd. 2 with an IC50 of 1.2+-0.4 micro M. Intriguingly, while compds. 1-5 exhibited similar cytotoxic properties between 1.2+-0.4 (2) and 4.0+-0.6 micro M (5), only compd. 2 showed a significant microtubule-stabilizing activity in vitro.