Studies on Absorption, Distribution, Excretion and Metabolism of Ginseng Saponins. VI. The Decomposition Products of Ginsenoside Rb_2 in the Stomach of Rats

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The decomposition of ginsenoside Rb_2 (Rb_2) in rat stomach (in vivo) and in 0.1 N HCl solution (in vitro) was investigated in detail. By treating with 0.1 N HCl, the acidity of which is similar to that of gastric juice, a part of Rb_2 was hydrolyzed to 20(R, S)-ginsenoside Rg_3. On the other hand, Rb_2 was little decomposed in rat stomach and a small quantity of an unidentified metabolite, which was different from the hydrolyzed products in 0.1 N HCl, was observed. The metabolite was separated into four compounds, which were identified by ^1H-and ^<13>C-nuclear magnetic resonance and fast atom bombardment mass spectrometry. These compounds were determined to be 25-hydroxy-23-ene (IV), 24-hydroxy-25-ene (V), 25-hydroperoxy-23-ene (VI) and 24-hydroperoxy-25-ene (VII) derivative of Rb_2,respectively.In this study, it is suggested that 20(S)-protopanaxatriol saponins undergo hydrolysis of the C-20 glycosyl moiety and hydration of the side chain, on the other hand, 20(S)-protopanaxadiol saponins undergo oxygenation of the side chain.
社団法人日本薬学会の論文
1991-02-25