Studies on the saponins of ginseng. IV. On the structure and enzymatic hydrolysis of ginsenoside-Ra1.

The presence of ginsenoside-Ra in Ginseng Radix has been demonstrated by thin-layer chromatography. Recently, ginsenoside-Ra was shown to be a mixture of more than two saponins. Among them, ginsenoside-Ra1 was isolated and its structure was determined on the basis of spectral, chemical and enzymatic hydrolysis evidence as 20 (S)-protopanaxadiol 3-O-β-D-glucopyranosyl (1→2)-β-D-glucopyranosido-20-O-β-D-xylopyranosyl (1→4)-α-L-arabinopyranosyl (1→6)-β-D-glucopyranoside (1). Besides compound K (8), three prosapogenins, 20 (S)-protopanaxadiol 3-O-β-D-glucopyranosido-20-O-β-D-glucopyranoside (7), 20 (S)-protopanaxadiol 3-O-β-D-glucopyranosido-20-O-β-D-xylopyranosyl (1→4)-α-L-arabinopyranosyl (1→6)-β-D-glucopyranoside (9), and 20 (S)-protopanaxadiol 20-O-β-D-xylopyranosyl (1→4)-α-L-arabinopyranosyl (1→6)-β-D-glucopyranoside (10) were obtained in the course of enzymatic hydrolysis of ginsenoside-Ra1. Further, 20 (S)-protopanaxadiol 3-O-β-D-glucopyranosido-20-O-α-L-arabinopyranosyl (1→6)-β-D-glucopyranoside (6), 7 and 8 were obtained by enzymatic hydrolysis of ginsenoside-Rb2 (4). The course of enzymatic hydrolysis of ginsenosides with naringinase is also discussed.