Abstract
The present study characterized in vitro metabolites of 20(R)-25-methoxyl-dammarane-3β, 12β, 20-triol (20(R)-25-OCH3-PPD) in mouse, rat, dog, monkey and human liver microsomes. 20(R)-25-OCH3-PPD was incubated with liver microsomes in the presence of NADPH. The reaction mixtures and the metabolites were identified on the basis of their mass profiles using LC-Q/TOF and were quantified using triple quadrupole instrument by multiple reaction monitoring. A total of 7 metabolites (M1-M7) of the phase I metabolites were detected in all species. 25(R)-OCH3-PPD was metabolized by hydroxylation, dehydrogenation, and O-demethylation. Enzyme kinetic of 20(R)-25-OCH3-PPD metabolism was evaluated in rat and human hepatic microsomes. Incubations studies with selective chemical inhibitors demonstrated that the metabolism of 20(R)-25-OCH3-PPD was primarily mediated by CYP3A4. We conclude that 20(R)-25-OCH3-PPD was metabolized extensively in mammalian species of mouse, rat, dog, monkey, and human. CYP3A4-catalyzed oxygenation metabolism played an important role in the disposition of 25(R)-OCH3-PPD, especially at the C-20 hydroxyl group.