Simultaneous Determination of 8 Compounds in Gancao-Ganjiang-Tang by HPLC-DAD and Analysis of the Relations between Compatibility, Dosage, and Contents of Medicines

Gancao-Ganjiang-Tang (GGT) is a traditional Chinese medicine (TCM) prescription and is a representative prescription for recuperating depleted Yang in Treatise on Febrile Diseases. The TCM theory believes that the efficacy of medicinal herbs is decided by the multicompounds which consist of different kinds of chemical constituents with bioactivities, but not by a monomeric constituent. From ancient times until today, GGT have 5 different kinds of compatibilities that can be verified. In this study, a HPLC-DAD method was established for the simultaneous determination of 8 compounds including 6-gingerol, 8-gingerol, 6-shogaol, liquiritin, liquiritigenin, isoliquiritin, isoliquiritigenin, and glycyrrhizic acid in the five GGT. The total contents of the 8 compounds in GGT varied from 555.56 to 956.33 μg/mL. The effects showed that the dosage and compatibility of medicinal herbs have influenced the content of chemical compounds of TCM prescription while the content of chemical compounds has acted on clinical efficacy. Quality evaluation and active essence screening of TCM (including single herb and prescription) should be based on the TCM theory and clinical effectiveness. The method was proven to be suitable for quality control of GGT.