Studies on Absorption, Distribution, Excretion and Metabolism of Ginseng Saponins. V. The Decomposition Products of Ginsenoside Rb2 in the Large Intestine of Rats

The decomposition of ginsenoside Rb2 (Rb2) in the rat large intestine after oral administration was investigated in detail. A part of Rb2 was decomposed and six decomposition products (I-VI) were observed on thin-layer chromatogram. Among them, five products (I-V) were isolated, and identification of these compounds was done by carbon-13 nuclear magnetic resonance (13C-NMR). On the basis of 13C-NMR analysis, these compounds were identified as ginsenoside Rd (I), 3-O-beta-D-glucopyranosyl-20-O- [alpha-L-arabinopyranosyl(1----6)-beta-D-glucopyranosyl]-20(S)- proto-panaxadiol (II), ginsenoside F2 (III), 20-O-[alpha-L-arabinopyranosyl(1----6)-beta-D-glucopyranosyl]-20(S )- protopanaxadiol (IV), and compound K (V), respectively.