In Vivo Metabolic Profiling of Equisetum debile Roxb. in Rats Based on High-Resolution Mass Spectrometry

Equisetum debile Roxb. (E. debile) is a traditional Chinese medicinal herb widely used for its diuretic, heat-clearing, and analgesic properties. Although increasing evidence has demonstrated its lipid-regulating, antioxidant, and anti-inflammatory activities, its in vivo metabolic profile and pharmacologically active constituents remain insufficiently characterized, limiting clinical application. In this study, UPLC-HRMS combined with advanced high-resolution mass spectrometry data processing was employed to systematically characterize the chemical constituents of E. debile and to investigate its absorption, distribution, metabolism, and excretion (ADME) in rats. E. debile was found to contain abundant organic acids, flavonoids, amino acids, and glycosides. Importantly, organic acids and flavonoid glycosides exhibited relatively high systemic exposure, suggesting their potential contribution as key in vivo bioactive constituents. Metabolic analyses revealed that flavonoids undergo oxidation, methylation, glucuronidation, and glutathione conjugation, whereas organic acids are primarily metabolized via decarboxylation and sulfation. In addition, several metabolites preferentially accumulated in bile, indicating the involvement of enterohepatic circulation. Overall, this study provides the first comprehensive and mechanistically informed characterization of the in vivo-exposed constituents and metabolic transformations of E. debile in rats, offering critical insights for its pharmacokinetic evaluation, mechanism of action studies, and modern clinical application.