Isolation, Analysis And Stability Of Epi - Isomers Of Glycyrrhizic Acid

glycyrrhizic acid is the main active ingredient of Radix Et Rhuzoma Glycyrrhizae,which is epimer.There areα-glycyrrhizic acid andβ-glycyrrhizic acid in nature and they can transform each other. The present study provides a method to determine the epimer of glycyrrhizic acid in Radix Et Rhuzoma Glycyrrhizae and Diammonium Glycyrrhizinate Injection by high performance liquid chromatography. Besides,α-glycyrrhizic acid andβ-glycyrrhizic acid are studyed on the Stability.（1） The standards ofα-glycyrrhizic acid andβ-glycyrrhizic acid are isolated from the crude drugs of Diammonium Glycyrrhizinate and Ammonium Glycyrrhizinate by Semi-preparative chromatography.（2） The present study provides a method to stimultaneous determine ofα-glycyrrhizic acid andβ-glycyrrhizic acid in Radix Et Rhuzoma Glycyrrhizae on the the first time. The chromatographic condition included a Hypersil C₁₈ column （250 mm×4.6 mm i.d, 5μm ） and the mobile phase consisting of Methanol-1 % acetic acid aqueous （66:34, v/v） and the absorbance was monitored at 250 nm.The calibration curve were linear over the range of 0.010 44-0.208 8 mg·mL^-1 （r = 0.999 5）and 0.051 88-1.038 mg·mL^-1 （r = 0.999 6）respectively .the mean recovery （n = 9）were 99.7 % and 99.4 % respectively and the RSD（n = 9） were 2.1 % and 2.3 % respectively .19 batches of Radix Et Rhuzoma Glycyrrhizae were analyzed under the same chromatographic condition.The results indicated that the cotents ofα-glycyrrhizic acid andβ-glycyrrhizic acid are different very much in Radix Et Rhuzoma Glycyrrhizae, but the ration ofβ-glycyrrhizic acid andα-glycyrrhizic acid’s cotents almost about at 13:1.（3） The present study provides a method to stimultaneous determination ofα-glycyrrhizic acid andβ-glycyrrhizic acid in Diammonium glycyrrhizinate injection on the the first time. The chromatographic condition included a Ultimate XB- C₁₈ column （250 mm×4.6 mm i.d, 5μm ） and the mobile phase consisting of Methanol-1 % acetic acid aqueous （60:40, v/v） and the absorbance was monitored at 250 nm.The calibration curve were linear over the range of 0.010 92-0.218 4 mg·mL-1 （r = 0.9998） and 0.005 19-0.103 8 mg·mL-1 （r = 0.999 8） respectively . the mean recovery （n = 9） were 98.5 % and 99.1 % respectively and the RSD（n = 9） were 2.4 % and 2.1 % respectively .3 batches of Diammonium glycyrrhizinate injection were analyzed under the same chromatographic condition.The results indicated that there are lots ofα-glycyrrhizic acid andβ-glycyrrhizic acid in Diammonium glycyrrhizinate injection. The assay was found to be simple and accurate to measure the concentrations ofα-glycyrrhizic acid andβ-glycyrrhizic acid in Diammonium glycyrrhizinate injection.（4）α-glycyrrhizic acid andβ-glycyrrhizic acid transformed each other under the certain conditions.The pretent study provided that the Stability ofα-glycyrrhizic acid andβ-glycyrrhizic acid during the process of extracting Radix Et Rhuzoma Glycyrrhizae and the Stability of their standards under the conditions of Light and ambient temperature. The results indicated thatα-glycyrrhizic acid andβ-glycyrrhizic acid can not transform each other during the process of extracting Radix Et Rhuzoma Glycyrrhizae, but their peak areas gradually decreased with the increasing of time. Their peak area do not transform significantly in the extenion of Radix Et Rhuzoma Glycyrrhizae under different temperatures.The peak area ofβ-glycyrrhizic acid gradually decreased and transformed toα-glycyrrhizic acid under the conditions of Light and ambient temperature,and they coexisten stably on the ration of 33:1.