Objective: To study the effect of glycyrrhetinic acid on the plasma concentration of kaempferol in rats. Method: Seventy-eight SD rats

weighing 150-210 g

half male and half female

were distributed into 4 groups

including control group of high concentration and low concentration

experimental group of high concentration and low concentration. Then each group was divided into three sub-groups

namely group of distribution phase (1 h)

equilibrium phase (2 h) and elimination phase (3 h). Experimental group of high concentration and low concentration was administered by gavage at a dose of 50 mg·kg-1 kaempferol mixed with 50 mg·kg-1 grycyrrhetinic acid and 25 mg·kg-1 mixed with 50 mg·kg-1 grycyrrhetinic acid

respectively. The control group was administered by gavage at a same dose like the experimental group except grycyrrhetinic acid. Plasma samples were collected by picking eyeballs 1

2

3 h after administration. Plasma was hydrolyzed at 90℃ for 120 min with hydrochloric acid. Then they were extracted with acetonitrile and concentration of kaempferol was determined by HPLC. Result: No free kaempferol was detected in rat's plasma after administration of kaempferol. The results showed that at two concentration levels there was no significant difference between two sets data of experimental group and control group

but there was significant difference (P<0.05) between two group at high concentration level in plasma(P<0.05). Conclusion: Grycyrrhetinic acid can affect the pharmacokinetics of kaempferol in plasma at high concentration level.