Triterpene Glycosides from the Stems of Akebia quinata

The stems of Akebia quinata have been analyzed for their triterpene glycoside constituents, resulting in the isolation of six new triterpene glycosides, along with 19 known ones. On the basis of extensive spectroscopic analysis, including 2D NMR data, and chemical evidence, the structures of the new compounds were deter-mined to be 3β-[(O-β-D-glucuronopyranosyl-(1→3)-α-L-arabinopyranosyl)oxy]olean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucuronopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]olean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucuronopyranosyl-(1→3)-α-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucuronopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3β-[(O-β-D-glucopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]-29-hydroxyolean-12-en-28-oic acid, and 3β-[(O-β-D-glucopyranosyl-(1→3)-O-[α-L-rhamnopyranosyl-(1→2)]-α-L-arabinopyranosyl)oxy]-23,29-dihydroxyolean-12-en-28-oic acid, respectively. The main triterpene glycosides contained in the stems of A. quinata were found to have two sugar units at C-3 and C-28 of the aglycone in this study, whereas those of Akebia trifoliate were reported to possess one sugar unit at C-28 of the aglycone. It may be possible to distinguish between A. quinata and A. trifoliate chemically by comparing their triterpene glycoside constituents.