Abstract: AIM:To study the urinary excretion of genistein at different doses in rats .METHODS:Sus- pended in 0 .5 %CMC-Na solution, genistein was orally administered to rats at the dose of 6 .25, 12 .5 and 50 mg·kg ^-1 , respectively .At various time intervals, the urine was collected .The urine was treated with β-glucu- ronidase.The genistein in urine was extracted twice by vortexing with 2 .0 ml mixture of methyl tert-tubtyl ether and pentane ( v/v =8 ∶2) .The organic phase was re- moved into the tubes and then evaporated in ventilation cabinet .The residue was dissolved in 50 μl of methanol . The solution of 20 μl was drawn and detected by high-per- formance liquid chromatography .RESULTS:The accu- mulative urine excretion of genistein was 34 .79 ±10 .83, 187 .30±69 .96 and 213 .56 ±30 .58 μg at the dose of 6 .25, 12 .5 and 50 mg·kg ^-1 , respectively .The total drug ( genistein +glucuronidated genistein) excreted from urine was 217 .79 ±52 .06, 583 .05 ±106 .92 and 1108 .37 ±88 .14 μg, and the ratio of glucuronidated genistein was 84 .03 %, 67 .88 % and 80 .73 % at the dose of 6 .25, 12 .5 and 50 mg·kg ^-1 , respectively . CONCLUSION:The genistein is excreted mainly in the form of glucuronidated genistein in rat urine .The genistein and glucuronidated genistein are excreted in the manner of non-linear dose-dependent .

Key words: genistein , urinary excretion , glucuroni- dation , HPLC