1987 Volume 2 Issue 6 Pages 665-672
A radioimmunoassay method for the determination of glycyrrhetic acid (GA) was developed. The measurable range of GA varied from 0.195 to 25 ng/tube and favorable accuracy was observed throughout the range (CV ; 5.8% for triplicate). The radioimmunoassay method described in this paper was superior to another analytical method in terms of sensitivity and simplicity. The serum concentrations of GA in the portal vein and vena cava were investigated after oral administration of 2.6 mg/kg of glycyrrhizin (GL) in rats. Cmax reached 575.5 ng/ml at 12 hr after administration in the portal vein, while it was 159.3 ng/ml at 18 hr in the vena cava. Serum levels of GA in both sites slowly decreased up to 34 hr, and approximately 200 ng/ml of GA was still maintained after 48 hr in the portal vein. Serum levels of GA in the vena cava was about 1/4 of that in the portal vein, suggesting first pass effect. AUC480 in the portal vein and vena cava were 16628.5 ng·hr/ml and 3370.5 ng·hr/ml, respectively. This method may be useful for the pharmacokinetic studies of GA.
