title: Studies on absorption, distribution, excretion and metabolism of ginseng saponins. VII. Comparison of the decomposition modes of ginsenoside-Rb1 and -Rb2 in the digestive tract of rats.
abstract: In order to clarify some similarities and differences of decomposition modes between 20(S)-protopanaxadiol (20(S)-ppd) saponins, represented by ginsenoside Rb1 (Rb1) and ginsenoside Rb2 (Rb2), the decompositions of Rb1 and Rb2 in the rat gastrointestinal tract, 0.1 N HCl and crude hesperidinase were investigated in detail. As in the case of Rb2 reported previously, Rb1 was hydrolyzed to 20(R,S)-ginsenoside Rg3 in 0.1 N HCl. On the other hand, hydroperoxidation of Rb1 occurred in rat stomach; the major hydroperoxide was separated and identified as the 25-hydroperoxy-23-ene derivative of Rb1 (VIII) by 1H- and 13C-nuclear magnetic resonance and fast atom bombardment mass spectrometry. The decomposition modes of 20(S)-ppd saponins (Rb1 and Rb2) differed from that of 20(S)-protopanaxatriol saponin (Rg1) in rat stomach. In rat large intestine, five decomposition products of Rb1 were observed by thin-layer chromatography, and these were identified as gypenoside XVII (G-XVII), ginsenoside Rd (Rd), ginsenoside F2 (F2), compound K (C-K) and VIII. The decomposition modes of Rb1 and Rb2, both 20(S)-ppd saponins, are considered to be different because of the hydrolysis rate in the terminal sugar moiety at the C-20 hydroxyl group in the rat large intestine. Using crude hesperidinase, Rb1 was decomposed to G-XVII, F2 and C-K, and Rb2 was decomposed to 3-O-beta-D-glucopyranosyl-20-O-[alpha-L-arabinopyranosyl(1----6)-b eta-D- glucopyranosyl]-20-(S)-ppd, F2 and C-K. Consequently, it appears that hydrolysis by beta-glucosidase, which is present in the rat large intestine, is distinct from that by crude hesperidinase.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: School of Pharmaceutical Sciences, University of Shizuoka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Karikura
authors.forename: T
authors.initials: T
authors.lastname: Miyase
authors.forename: H
authors.initials: H
authors.lastname: Tanizawa
authors.forename: T
authors.initials: T
authors.lastname: Taniyama
authors.forename: Y
authors.initials: Y
authors.lastname: Takino
mesh_terms: D000818:Animals; D004064:Digestive System / Q000378:metabolism*; D036145:Ginsenosides; D007408:Intestinal Absorption; D005894:Panax / Q000378:metabolism*; D010946:Plants, Medicinal; D051381:Rats; D012503:Saponins / Q000378:metabolism / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D036145:Ginsenosides; D012503:Saponins; C048026:ginsenoside Rb2