Optimized LC–ESI-ion trap MS to determine simultaneously isocorynoxeine and its phase I and II metabolites in rats with application to pharmacokinetics and mass balance investigation

Abstract

ABSTRACTIsocorynoxeine (ICOR) is one of the bioactive oxindole alkaloids in Uncaria species. This study presents the pharmacokinetics and mass balance of ICOR in rats after oral dose of 40.0 mg/kg and intravenous dose of 4.0 mg/kg through detection of ICOR and its in vivo metabolites, using an optimized LC-MS with recoveries ranged from 94 to 104%, accuracy varied from 96 to 103%, and relative standard deviation for assay being less than 5%. ICOR reached its Cmax of 336.7 ng/mL in plasma 3 hr after oral dose. The phase I metabolites of ICOR, 11-hydroxyisocorynoxeine (M1), and 10-hydroxyisocorynoxeine (M2) were detected in rat heart, kidneys, urine, and feces; whereas, in rat liver and bile, M1, M2, along with phase II metabolites, 11-hydroxyisocorynoxeine 11-O-β-D-glucuronide, and 10-hydroxyisocorynoxeine 10-O-β-D-glucuronide were identified. ICOR (77.0%) was excreted into feces and urine after oral administration within 72 hr, 0.93% drained into bile in 8 hr, 17.9% biotransformed into M1 and M2 at a ratio of ca. 1:1, and 0.028% detected in main organs at tmax, in which brain uptake index is 3.2 ng/g. This work affords a developed and validated LC-MS for simultaneous determination of ICOR and its in vivo metabolites with improved precision and accuracy.