Preclinical metabolism and metabolic drug–drug interaction profile of pedunculoside and rotundic acid

Pedunculoside and rotundic acid, the most abundant components in plants of the genus Ilex L. (Aquifoliaceae), exhibit biological and pharmacological significance in the treatment of cardiovascular diseases. However, there have been few studies on their metabolism. This study performed a systematic metabolism study of pedunculoside and rotundic acid and evaluated their potential for herb-drug interaction. Pedunculoside or rotundic acid was incubated with human liver microsomes and recombinant human metabolic enzymes, and analyzed using LC-Q-TOF/MS and LC-MS/MS. Pedunculoside was found to be the most stable in human liver microsomes, whereas rotundic acid was easily metabolized. Eight pedunculoside metabolites and six rotundic acid metabolites were detected and tentatively identified through hydroxylation, glucuronidation, acetylation, and glucose conjugation. Hydroxylation of pedunculoside is mainly catalyzed by CYP3A4/5 and partly by CYP2C8. Hydroxylation of rotundic acid is almost exclusively catalyzed by CYP3A4/5, and its glucuronidation reaction is mediated by UGT1A4. Neither pedunculoside nor rotundic acid showed CYP inhibition (IC₅₀ values > 50 μM) with the probe substrates of major CYP isoforms during incubation with human liver microsomes. This study is the first investigation into the in vitro metabolism of pedunculoside and rotundic acid using human liver microsomes. It also aims to assess their potential as perpetrators of drug-drug interactions involving CYP enzymes. The comprehensive metabolism and drug interaction studies of pedunculoside and rotundic acid enable us to evaluate and manage potential risks with their use in pharmacotherapy.