Systemic Exposure and Multicomponent Pharmacokinetics of Mailuoning Oral Liquid: Integrated Ultra-High-Performance...

Mailuoning oral liquid (MLN) is a state-approved multi-herb formula that has been prescribed for 25 years to clear heat, nourish yin, invigorate blood, and resolve stasis. Although randomized controlled trials and real-world evidence support its efficacy in thromboangiitis obliterans, deep-vein thrombosis, and the convalescent phase of cerebral infarction, a systematic search identified no pharmacokinetic data on its bioactive constituents. This lack of pharmacokinetic data impedes evidence-based dose refinement and international acceptance. Here, we employed ultra-high-performance liquid chromatography with Quadrupole-Exactive Orbitrap high-resolution mass spectrometry (UHPLC-Q-Exactive Orbitrap HRMS) to track 39 MLN-derived compounds in rat plasma, intestinal contents, and 10 tissues; 15 with prominent systemic exposure were designated as key pharmacokinetic markers. A selective and sensitive UHPLC-tandem MS assay was subsequently developed and fully validated for simultaneous quantification of these 15 circulating components. The assay exhibited excellent linearity (r ≥ 0.9974) for all analytes, with precision, accuracy, extraction recovery, and matrix effects meeting standard bioanalytical validation criteria. All compounds demonstrated stability under the tested storage conditions. Following oral administration of MLN at 8.1 and 16.2 mL·kg^-1 in rats, all 15 components were rapidly absorbed, reaching peak plasma concentrations within approximately 1 h. Systemic exposure increased in a clear dose-dependent manner, with structurally related compounds showing similar pharmacokinetic profiles. Notably, the iridoids secoxyloganin, harpagide, and secologanic acid yielded the highest AUC₀-_24 h values, indicating they are the principal systemic exposure markers. This study establishes the first comprehensive pharmacokinetic profile for MLN and provides a robust, validated analytical platform. By creating a crucial link between quantitative systemic exposure and efficacy, our work supplies a scientific foundation for refining dosage regimens, establishing quality specifications, and promoting the evidence-based clinical application of this widely prescribed traditional Chinese medicine formula.