Abstract:  Soybean isoflavones is a type of secondary metabolic product and belong to polyphenolic substance. Isoflavones are abundant micronutrients in our diet of legume,and evidence for their role of in the prevention of degenerative disease such as cancer,cardiovascular disease,diabetes,and hyperlipidemia and so on are emerging. To further study on the bioefficacy of isoflavones related to biological metabolism,the maximal plasma concentration (Cmax),the time to reach the maximal plasma concentration (Tmax),the area under the plasma concentration-time curve (AUC),the elimination half-life (t1/2),and the relative dejection excretion which all describe the parameter of isoflavones pharmacokinetics were calculated using KM mice test. This experiment obtained better results in measurement isoflavones content with methanol as the solvent for isoflavones and by ultraviolet spectrophotometer; there was two dose of 10mg/kg and 20mg/kg in laboratory animal with i.g. and results was manifestative that plasma concentration was 0.65μg/ml by low doses and 0.75μg/ml by high dose. Moreover,the first-pass elimination in high dose happened; Two groups of dose almost had no differences in elimination half-life; Excretion from dejection was 19.87% of the intake of isoflavones in 24 hours. So it is considerable that urinary excretion is primary and hepato-enteral circulation is secondary in excretion pathway of isoflavones.

Key words: isoflavones, absorption, excretion, pharmacokinetics