The C-glucosyl bond of puerarin was cleaved hydrolytically by a human intestinal bacterium strain PUE to yield its aglycone daidzein and an intact glucose

C-Glycosides are usually resistant against acidic hydrolysis and enzymatic treatments because C-1 of the sugar moiety is directly attached to the aglycone by C-C bonding. Nevertheless, a human intestinal bacterium, strain PUE, can cleave the C-glucosyl bond of puerarin to yield its aglycone daidzein. ¹⁾ To clarify the mechanism of the cleaving reaction, we tried to identify the structure of the metabolite derived from the sugar moiety of puerarin. To detect it easily, deuterium labeled puerarin, [6″,6″- D₂]puerarin, was prepared in 7 steps. Sugars contained in a metabolite mixture from [6″,6″-D₂]puerarin was analyzed by an HPLC-electrospray ionization (ESI)-MS method after treatment of sugars with 1-phenyl-3-methyl-5-pyrazolone (PMP). Since deuterium labeled glucose was detected in the metabolite mixture of [6″,6″-D₂]puerarin, we concluded that puerarin was metabolized to daidzein and an intact glucose by strain PUE. As C-1 of the sugar was hydroxylated instead of hydrogenating, C-glucosyl bond-cleaving reaction is not reduction but hydrolysis. This is the first report of revealing the reaction manner and the exact products of C-glucosyl bond-cleaving reaction.