Use of an UHPLC-MS/MS Method for Determination of Kuraridin and Characterization of Its Metabolites in Rat Plasma after Oral Administration.

Kuraridin is an active natural prenylated flavonoid ingredient originating from the well-known traditional Chinese medicine Sophora flavescens Ait., that possesses various bioactivities, such as antitumor activity, PLCγ1 inhibitory activity, glycosidase inhibitory activity, etc. However, there is no report on the plasma metabolic profile and pharmacokinetic study of kuraridin. The current study was designed to use an ultra-performance liquid chromatography/tandem mass spectrometry (UHPLC-MS/MS) method for the quantification and characterization metabolites in rat plasma after oral administration of kuraridin. A liquid-liquid extraction method with ethyl acetate-acetonitrile (1:3) was used to extract the kuraridin from rat plasma samples. The chromatographic separation was carried out on a Hypersil GOLD UHPLC C18 column equipped with a C18 guard cartridge using a gradient elution with organic solvent-water as mobile phase. Based on comparing the retention times with reference standards or on the basis of MS₂ fragmentation behaviors, a total of 19 metabolites were identified or tentatively characterized from rat plasma. Under the optimized conditions, the method showed good linearity (r² > 0.99) over the ranges of 1-500 ng/mL for kuraridin. The inter- and intra-day precisions were less than 8.95%, and the accuracy was in the range of -6.27-6.48%. The recovery of kuraridin ranged from 90.1% to 100.4%. The developed UHPLC-MS/MS method was thus successfully applied in the qualitative of metabolites and quantitative analysis of kuraridin in rat plasma.