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

Abstract

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. 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.