Comparative pharmacokinetic behavior of glycyrrhetic acid after oral administration of glycyrrhizic acid and Gancao-Fuzi-Tang

Comparative pharmacokinetic profiles of glycyrrhetic acid (GA), glycyrrhizic acid (GL) and Gancao-Fuzi-Tang (KF) after oral administration of GL and KF were studied. Plasma samples taken from rats were acidified with acetic acid and GA was extracted with isopropanol-ethyl ether (1 : 1). Separation of GA was performed on a C,, column with the detection wavelength set at 254nm. The mobile phase was methanol-acetonitrile-water-acetic acid (58 :18 : 24 : 1 v/v). The results showed that the mean residence time and area under the curve of GA in KF-administered rats were 27.6 +/- 1.5 h and 122.8 +/- 46.7 mug(.)h/ml respectively, which were significantly different from those in GL-administered rats (15.0 +/- 2.0 h and 40.9 +/- 9.6 mug(.)h/ml, respectively). The results suggest the increased effect of GA after oral administration of KF in comparison with GL.