Abstract
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-${\alpha}$-L-arabinopyranosyl hederagenin (${\delta}$-hederin), 3-O-${\alpha}$-L-rhamnopyranosyl (1${\rightarrow}$2) ${\alpha}$-L-arabinopyranoly oleanolic acid (${\beta}$-hederin), 3-O-${\beta}$-D-xylopyranosyl (1${\rightarrow}$3) ${\alpha}$-L-arabinopyranosyl hederagenin (saponin C), and 3-O ${\alpha}$-L-rhamnopyranosyl (1${\rightarrow}$2) ${\alpha}$-L-arabinopyranosyl hederagenin (${\alpha}$-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. ${\beta}$-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 ${\alpha}$-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.
생리활성에 따른 용매분획을 통해 으름(Akebia quinata) 과피로부터 4종의 사포닌을 분리하였다. 으름 과피를 에탄올로 추출한 후 디클로로메탄, 에틸아세테이트, 부탄올 및 물 층으로 순차분획하였으며 분광학적 분석을 통해 부탄올 분획으로부터3-O-${\alpha}$-L-arabinopyranosyl hederagenin (${\delta}$-hederin), 3-O-${\alpha}$-L-rhamnopyranosyl (1${\rightarrow}$2) ${\alpha}$-L-arabinopyranoly oleanolic acid (${\beta}$-hederin), 3-O-${\beta}$-D-xylopyranosyl (1${\rightarrow}$3) ${\alpha}$-L-arabinopyranosyl hederagenin (saponin C), 및 3-O-${\alpha}$-Lrhamnopyranosyl (1${\rightarrow}$2) ${\alpha}$-L-arabinopyranosyl hederagenin(${\alpha}$-hederin)을 구조동정하였다. 또한, 산분해 분석을 통해 oleanolic acid 및 hederagenin을 해당 sapogenin으로 확인하였다. 이들 화합물들은 HepG2 간암세포에서 강력한 세포독성을 나타내었으며 ${\beta}$-hederin의 경우 항세포사멸단백질인 bcl-2의 발현을 억제하는 것으로 나타났다. 분리한 모든 화합물은 세포사멸유도효소인 caspase-3의 효소활성을 촉진하였으며 이중 ${\alpha}$-hederin의 활성이 가장 우수한 것으로 확인되었다. 본 연구를 통해 으름의 세포자살유도활성을 최초로 보고하는 바이며 이러한 결과는 으름이 향후 천연항암제로 사용될 수 있는 가능성을 제시하고 있다.
