Cytotoxic and Apoptotic Effects of Saponins from Akebia quinata on HepG2 Hepatocarcinoma Cells

Cytotoxic and Apoptotic Effects of Saponins from Akebia quinata on HepG2 Hepatocarcinoma Cells

Four saponins (1~4) were isolated from Akebia quinata pericarp through bioassay-guided fractionation. Pericarps of A. quinata were extracted with ethanol and sequentially fractionated with dichloromethane, ethyl acetate, butanol and water. Compounds 1~4 from the butanol fraction were identified as 3-O-α-L-arabinopyranosyl hederagenin (δ-hederin), 3-O-α-L-rhamnopyranosyl (1→2) α-L-arabinopyranoly oleanolic acid (β-hederin), 3-O-β-D-xylopyranosyl (1→3) α-L-arabinopyranosyl hederagenin (saponin C), and 3-O-α-L-rhamnopyranosyl (1→2) α-L-arabinopyranosyl hederagenin (α-hederin) based on the spectroscopic evidences, respectively. Oleanolic acid and hederagenin were identified as the corresponding sapogenins by acid‐hydrolysis. These compounds exhibited strong cytotoxic activity in MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxy-methoxyphenyl)-2-(4-sulfophenyl)-2H- tetrazolium, inner salt] assay on HepG2 cells. β-Hederin obviously attenuated the expression of bcl-2, an anti‐apoptotic protein. All of the compounds also induced the activity of caspase-3, an apoptotic enzyme, while α-hederin was the most potent activator of the enzyme. Our data demonstrate for the first time the apoptosis-inducing activity of A. quinata. These results suggest that A. quinata could be used as a potential source of natural cancer chemopreventive agents.

Four saponins (1~4) were isolated from Akebia quinata pericarp through bioassay-guided fractionation. Pericarps of A. quinata were extracted with ethanol and sequentially fractionated with dichloromethane, ethyl acetate, butanol and water. Compounds 1~4 from the butanol fraction were identified as 3-O-α-L-arabinopyranosyl hederagenin (δ-hederin), 3-O-α-L-rhamnopyranosyl (1→2) α-L-arabinopyranoly oleanolic acid (β-hederin), 3-O-β-D-xylopyranosyl (1→3) α-L-arabinopyranosyl hederagenin (saponin C), and 3-O-α-L-rhamnopyranosyl (1→2) α-L-arabinopyranosyl hederagenin (α-hederin) based on the spectroscopic evidences, respectively. Oleanolic acid and hederagenin were identified as the corresponding sapogenins by acid‐hydrolysis. These compounds exhibited strong cytotoxic activity in MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxy-methoxyphenyl)-2-(4-sulfophenyl)-2H- tetrazolium, inner salt] assay on HepG2 cells. β-Hederin obviously attenuated the expression of bcl-2, an anti‐apoptotic protein. All of the compounds also induced the activity of caspase-3, an apoptotic enzyme, while α-hederin was the most potent activator of the enzyme. Our data demonstrate for the first time the apoptosis-inducing activity of A. quinata. These results suggest that A. quinata could be used as a potential source of natural cancer chemopreventive agents.