Investigation of the Chemical Constituents and Hepatic‐Exposed Components of the Bupleuri Radix–Rhei Radix et Rhizoma Herbal Pair Based on UPLC‐Q‐Orbitrap‐MS Analysis

BACKGROUND: Bupleuri Radix (BR) and Rhei Radix et Rhizoma (RR) are commonly used in combination in traditional Chinese medicine, yet the chemical basis of their compatibility and the liver-exposed constituents after oral administration remain unclear. OBJECTIVE: To systematically characterize the chemical constituents of the Bupleuri Radix-Rhei Radix et Rhizoma (BR-RR) aqueous extract and to investigate the exposed prototype components and metabolites in mouse liver after oral administration. METHODS: UPLC-Q-Orbitrap-MS was employed to comprehensively analyze the chemical constituents of the BR-RR aqueous extract and the liver-exposed components in mice after gavage administration. Compound identification was performed by integrating retention times, accurate molecular weights, and multistage MS fragmentation data. RESULTS: A total of 109 compounds were tentatively identified in the BR-RR aqueous extract, including anthraquinones, saponins, flavonoids, phenols, and organic acids. In mouse liver samples, 25 prototype components and 21 metabolites were tentatively characterized after oral administration, among which anthraquinones were the predominant chemical class. These findings revealed the major in vivo exposed constituents and metabolic characteristics of the BR-RR extract in the liver. CONCLUSIONS: This study systematically characterized the chemical constituents of the BR-RR aqueous extract and elucidated its liver exposure profile in mice. The findings provide an overall view of the in vivo exposure and metabolic characteristics of the extract and offer useful reference information for quality evaluation and further investigation of its material basis.