A comparison of the distribution of two glycyrrhizic acid epimers in rat tissues.

The distribution characteristics of two glycyrrhizic acid (GL) epimers, i.e. alpha-GL and beta-GL in rat tissues were examined. At 5, 15, 30, 60, and 180 min after i.v. administration of a single alpha-GL or beta-GL injection (21.0 mg/kg) in rats, the concentrations of these epimers in rat tissues were determined by reverse phase-high performance liquid chromatography (RP-HPLC) using the internal standard method. Alpha-GL and beta-GL were both rapidly distributed in the tissues. The concentrations of alpha-GL in the liver were significantly higher than those of beta-GL, but were lower than or similar to those of beta-GL in the other tissues. The concentrations of alpha-GL in all the tissues declined rapidly, and were lower than or similar to the detection limit for quantification at 180 min after i.v. administration. However, beta-GL concentrations remained rather high in the tissues, and maintained 10-50% of their peak value. According to these results, distinct differences were found in the distribution and metabolism in the rat tissues after i.v. administration of the two GL epimers, with these differences being closely related to the different configuration of alpha-GL and beta-GL.