Liquid chromatography/mass spectrometry-based structural analysis of soyasaponin Ab metabolites by human fecal microflora

Soyasaponin Ab, a major constituent of soybean by human intestinal microflora, was anaerobically incubated with fecal suspensions from ten individuals for 48 h and its metabolites were measured by LC–MS/MS analysis. Ten metabolites were detected. The spectra of the parental constituent soyasaponin Ab showed a peak at m/z 1435 [M−H]− ion and those of its nine metabolites showed peaks at m/z 1310.0 [M-3C2H2O-H]− ion, m/z 1267.9 [M-4C2H2O-H]− ion, m/z 1105.3 [M-Glc-4C2H2O-H]− ion, m/z 973.2 [M-Glc-Ara-4C2H2O-H]− ion, m/z 943.4 [M-2Glc-4C2H2O-H]− ion, m/z 811.1 [M-2Glc-Ara-4C2H2O-H]− ion, m/z 781.2 [M-2Glc-Gal-4C2H2O-H]− ion, m/z 649.0 [M-2Glc-Gal-Ara-4C2H2O-H]− ion, and m/z 458.8 [Soyasapogenol A + H]+ ion. Metabolic activity varied significantly between individuals. The metabolic pathway was classified into two groups: the first group potently produced soyasapogenol A and the second group accumulated soyasapogenol A 3-β-d-glucuronide.