Systematic comparison of metabolic differences of Uncaria rhynchophylla in rat, mouse, dog, pig, monkey and human liver microsomes.

Metabolites have a close relationship with the efficacy and safety of herbal medicines. However, ubiquitous matrix interferences, complex co-elution, and minor or trace amounts in plasma restrict the comprehensive identification of metabolites. In this study, an efficient strategy comprising a mass defect filter and time-staggered targeted ion lists was established to characterize the metabolites of alkaloids of Uncaria rhynchophylla (UR) for the systematic comparison of metabolic differences in rat, mouse, dog, pig, monkey and human liver microsomes. The mass defect filter model effectively decreased interfering ions by 63-68%, and time-staggered precursor ion lists significantly increased the number of triggered MS/MS fragmentation by 65-120% in liver microsomes of six species. Ultimately, a total of 165 metabolites in the liver microsomes of six species were tentatively characterized, and the main metabolic pathways were demethylation, isomerization, hydrolysis, oxygenation and dehydrogenation. The results showed that the mouse liver microsomes exhibited metabolic behavior most similar to human metabolism of UR alkaloids. We hope that these results provide basic data for further investigation of UR metabolism in different species, and that the strategy can provide a reference for metabolite characterization of herbal medicines in complex biological matrix. Graphical abstract.