Characterization Using LC/MS of the Absorption Compounds and Metabolites in Rat Plasma after Oral Administration of a Single or Mixed Decoction of Shaoyao and Gancao

Shaoyao-Gancao decoction (SGD), a traditional Chinese formulation containing Paeoniae Radix (SY) and Glycyrrhizae Radix (GC), is commonly used to relieve abdominal pain. However, the absorption and metabolites of the characteristic constituents of the two herbs in vivo have been reported rarely. The purpose of this study was to investigate the compatibility rationality and the mechanism of the enhanced efficiency of SGD. A single or a mixed decoction (SG and S+G, respectively) was orally administered to rats. Blood samples were collected at different intervals following treatment and analyzed by liquid LC/MS. A total of fifteen ingredients (denoted as M1 to M15) were found in both rat plasma after treatment with the two decoctions. Furthermore, the proposed structures of the remained twelve ingredients were obtained except M9, M10 and M15. The quality of the ingredients in the rat plasma showed no significant difference between the two decoctions. However, the quantity of twelve ingredients differed greatly, indicating that the absorption of SG was greater than that of S+G except M7, M12 and M15. As the compositions associated with the efficacy of SG and S+G were inconsistent, the degree of the absorption of the 15 ingredients by the gastrointestinal tract were different, which caused a significantly enhanced efficacy of certain ingredients. This study presents an exploration of the mechanism behind the improved efficacy of individual components in traditional Chinese medicine therapies through combination with other components.