Pericarp saponins of Akebia quinata Decne. I. Glycosides of hederagenin and oleanolic acid.
Abstract
Two free triterpenoids and twelve triterpenoid saponins were isolated from the fresh pericarps of Akebia quinata DECNE. (Lardizabalaceae). Ten saponins, PA-G, PJ2, PJ3 and PK, of the above twelve were characterized as follows : PA (I), hederagenin (hederag.) 3-O-α-L-ara·pyranoside ; PF (II), hederag. 3-O-β-D-glc·pyr-(1→2)-α-L-ara·pyranoside ; PB (III), oleanolic acid (ol. acid) 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranoside ; Pc (VI), hederag. 3-O-β-D-xyl·pyr-(1→3)-α-L-ara·pyranoside ; PD (IX), hederag. 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranoside ; PE (XI), ol, acid 3-O-β-D-glc·pyr-(1→2)-α-L-ara·pyranoside ; PG (XIII), hederag. 3-O-β-D-xyl·pyr-(1→3)-α-L-rha·pyr-(1→2)-α-L-ara·pyranoside ; PJz (XV') 3-O-α-L-ara·pyranosyl-hederag. 28-O-α-L-rha·pyr-(1→4)-β-D-glc·pyr-(1→6)-β-D-glc·pyranoside ; PJs (XIX'), 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranosyl-ol. acid 28-O-α-L-rha·pyr-(1→4)-β-D-glc·pyr-(1→6)-β-D-glc·pyranoside ; PK (XXI), 3-O-α-L-rha·pyr-(1→2)-α-L-ara·pyranosyl-hederag. 28-O-α-L-rha·pyr-(1→4)-β-D-glc·pyr-(1→6)-β-D-glc·pyranoside. VI, XI and XV'are new members of the group of hederagenin and oleanolic acid oligoglycosides. It is noted that they all have the common unit, 3-O-α-L-ara·pyranoside, and that XV', XIX'and XX, having the same trisaccharide combined with the 28-carboxyl group of the aglycone, are corresponding to I, III and IX, respectively.