Pharmacokinetics and tissue distribution of Yigong San in rats

Ethnopharmacological relevance: In traditional Chinese medicine (TCM), Yigong San (YGS) is mainly used to treat dyspepsia caused by deficiency of spleen and stomach qi. Although the chemical composition and bioactivity of YGS has been well studied, the main in vivo compounds and their distribution in tissues still need to be made clearer. Aim of the study: To elucidate the pharmacokinetic profiles and tissue distribution of eight main compounds of YGS in rats, and provide a reference for clinical application and new drug development. Materials and methods: UPLC-Q-Exactive-Orbitrap-MS was used to qualitatively characterize the parent compounds and their metabolites in the plasma of rats after oral administration of YGS. A sensitive, reliable, and accurate ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method using UPLC-AB Sciex QTRAP 5500 MS was established to quantitatively determine eight main compounds of YGS in rat plasma and tissues, including liquiritin, isoliquiritin, hesperidin, ginsenosides Rb1, Re and Rg1, atractylenolides I and II. Results: The mean area under the concentration-time curve (AUC) values of ginsenoside Rb1, hesperidin, and liquiritin at low, medium, and high doses were greater than 150 ng h/mL. The elimination half-life (t1/2) values of ginsenoside Rb1, atractylenolides I and II (low and medium doses) were longer than 10 h. Peak time (Tmax) values of all compounds were shorter than 10 h. Except for atractylenolides, the maximum concentration (Cmax) values of the compounds were greater than 10 ng/mL. The eight compounds were detected in the heart, brain, liver, spleen and kidney at 0.25 h after oral administration. Liquiritin and isoliquiritin had higher exposure in the liver and heart. Hesperidin and ginsenosides Rb1, Re, and Rg1 are mainly distributed in the spleen and kidney. Atractylenolides I and II are mainly distributed in spleen, liver and kidney. Conclusions: All main compounds of YGS, i.e., liquiritin, isoliquiritin, hesperidin, ginsenosides Rb1, Re, and Rg1, and atractylenolides I and II are absorbed into plasma and widely distributed in various tissues. Among them, hesperidin, ginsenoside Rb1, and atractylenolide I are main in vivo compounds. They are mainly distributed in spleen, liver and kidney. The results of this study provide a basis for further in-depth development and application of YGS.