Comparison of Cytoprotective Effects of Saponins Isolated from Leaves of Aralia elata SEEM. (Araliaceae) with Synthesized Bisdesmosides of Oleanoic Acid and Hederagenin on Carbon Tetrachloride-Induced Hepatic Injury

Abstract

Glycosylations of 3-O-{2, 3, 4-tri-O-acetyl-α-L-rhamnopyranosyl(1→2)-3, 4-di-O-acetyl-α-L-arabinopyranosyl}-23-O-acetylhederagenin (15) with mono- (16), di- (17) and trisaccharide bromide (18) gave the bisdesmoside peracetates 19, 20 and 22, respectively, which were treated with 5% KOH in MeOH to give the bisdesmosides 25-27. Hydrolysis of the glycosides 6 and 9 having β-D-glucopyranose as a terminal sugar component with β-glucosidase in acetate buffer (pH 4.7) gave compounds 28 and 29, respectively. Cytoprotective effects of the synthesized triterpenoidal saponins against CCl₄-induced hepatic injury were compared with those of saponins isolated from the leaves of Aralia elata SEEM. (Araliaceae) using isolated hepatocytes from rat liver. Although the monodesmosides 1-4 having neutral sugar components only at the O-3 position on the aglycones showed no cytoprotective effect, bisdesmosides having sugar components at both the O-3 and O-28 positions on the aglycones had potent effects, even when the species of the sugar components were different. The bisdesmosides 10, 11, and 27 having five monosaccharides in the molecules exhibited the most potent cytoprotective effects.