[Metabolism of six saponins by rat intestinal bacteria in vitro]

Abstract

To investigate the metabolism of six saponins by rat intestinal bacteria in vitro.Six saponins, including notoginsenoside R₁, ginsenoside Rg₁, ginsenoside Rg₂, ginsenoside Re, ginsenoside Rd and ginsenoside Rb₁, were incubated for 8 and 24 h with rat intestinal bacteria under anaerobic environment, respectively. After the samples were precipitated by acetonitrile and extracted with ethyl acetate, LC-Q-TOF-MS/MS was applied for the qualitative analysis of the metabolites. The potential metabolites in rat feces were analyzed by comparing the total ion current of the test samples and blank samples and analyzing the quasi-molecular ion and fragment ion of all chromatograms. The results showed that six saponins could be easily metabolized by rat intestinal bacteria. Notoginsenoside R₁ was mainly metabolized into five metabolites, and it's metabolic pathway was notoginsenoside R₁→ginsenoside Rg₁→ginsenoside Rh₁ and ginsenoside F₁→protopanaxatriol→dehydrogenated protopanaxatriol. Ginsenoside Rg₁ was mainly metabolized into four metabolites, and it's metabolic pathway was ginsenoside Rg₁→ginsenoside Rh₁ and ginsenoside F₁→protopanaxatriol→dehydrogenated protopanaxatriol. Ginsenoside Rg₂ was mainly metabolized into two metabolites, and it's metabolic pathway was ginsenoside Rg₂→ protopanaxatriol→dehydrogenated protopanaxatriol. Ginsenoside Re was mainly metabolized into four metabolites, and it's metabolic pathway was ginsenoside Re→ginsenoside Rg₂→ginsenoside F₁→protopanaxatriol→dehydrogenated protopanaxatriol. Ginsenoside Rd was mainly metabolized into four metabolites, and it's metabolic pathway was ginsenoside Rd→ginsenoside Rg₃ and ginsenoside F₂→ginsenoside Rh₂→protopanaxadiol. Ginsenoside Rb1 was mainly metabolized into five metabolites, and it's metabolic pathway was ginsenoside Rb₁→ginsenoside Rd→ginsenoside Rg₃ and ginsenoside F₂→ginsenoside Rh₂→protopanaxadiol. In summary, six saponins could be quickly metabolized by rat intestinal bacteria in vitro. Their major metabolic pathways were deglycosylation and dehydrogenation.

Keywords: LC-Q-TOF-MS/MS; deglycosylation; metabolism; rat intestinal bacteria; saponins.