Objective: To establish an UPLC-MS method for determining the content of daidzein in rat plasma

and compare pharmacokinetic parameters of daidzein in rats after gavage of compound Naomaitong and Puerariae Lobatae Radix extract for evaluating effects of other ingredients in compound Naomaitong extract on pharmacokinetics of daidzein. Method: Twelve rats were randomly divided into two groups

gastric gavage of compound Naomaitong and Puerariae Lobatae Radix extract according to 1.002 5 mg·kg-1 of daidzein

plasma samples collected at different time

and then using UPLC-MS to determine plasma concentrations of daidzein

pharmacokinetic parameters were calculated by DAS 2.0 software

and its one-way ANOVA with SPSS 16.0 software. Result: There was a good linearity over concentration ranges of 6.175-741.0 μg·L-1

limit of quantitation was 6.175 μg·L-1

the lowest detection limit was 1.235 μg·L-1.Cmax and CL/F of daidzein from compound Naomaitong and Puerariae Lobatae Radix extract were significantly different

the other parameters were not significantly different. Conclusion: This UPLC-MS is sensitive

accurate

specific and applicable to determine in vivo plasma concentration of drug with daidzein as a main ingredient.Other ingredients in compound Naomaitong extract have a great impact on absorption and removal of daidzein

so that Cmax and CL/F of daidzein decrease.