UHPLC‐MS/MS‐Based Quantification of 14 Renshen Guben Oral Liquid–Related Constituents in Cancer Patients With Neutropenia

ABSTRACT Objectives This study aimed to develop and validate a UHPLC‐MS/MS method for the simultaneous determination of 14 constituents related to Renshen Guben Oral Liquid (RSGB) in human plasma and to explore concentration–absolute neutrophil count (ANC) associations in cancer patients with chemoradiotherapy‐induced neutropenia (CIN). Methods Candidate constituents were selected by integrating chemical representativeness, disease relevance, reference standard availability, and analytical feasibility, with support from network pharmacology. Plasma samples were collected from 25 patients before administration and at 1 and 2 h after RSGB administration. Samples were processed by liquid–liquid extraction using methyl tert‐butyl ether or n‐butanol and analyzed by UHPLC‐MS/MS. Spearman correlation analysis was used to assess exploratory associations between post‐dose concentrations of major quantifiable circulating constituents and ANC change from baseline to Day 15. Results The assay fulfilled predefined bioanalytical acceptance criteria and enabled simultaneous quantification of 14 RSGB‐related constituents in human plasma. Ginsenoside Rb1 (G‐Rb1), ginsenoside compound K (G‐CK), and paeonol (PAE) were the major quantifiable circulating constituents, whereas protopanaxadiol (PPD) and protopanaxatriol (PPT) were only sporadically quantifiable. Exploratory analyses showed positive associations between concentrations of G‐Rb1, G‐CK, and PAE and ΔANC. Molecular docking provided complementary computational support for potential target interactions. Conclusions G‐Rb1, G‐CK, and PAE were the major quantifiable circulating RSGB‐related constituents within the early sampling window, and their concentrations showed exploratory associations with ANC change. These findings provide complementary in vivo evidence for evaluating RSGB‐related constituents.