Metabolism of puerarin and daidzin by human intestinal bacteria and their relation to in vitro cytotoxicity.

When puerarin or daidzin were incubated for 24 h with human intestinal bacteria, two metabolites, daidzein and calycosin, were produced from them, respectively. The metabolic time course of puerarin was as follows: at an early time, puerarin was converted to daidzin, and then calycosin. The metabolic time course of daidzin by human intestinal bacteria was also similar to that of puerarin. The in vitro cytotoxicities of these metabolites, calycosin and daidzein, were superior to those of puerarin and daidzein.