Simultaneous Determination of Six <i>Uncaria</i> Alkaloids in Mouse Blood by UPLC–MS/MS and Its Application in Pharmacokinetics and Bioavailability
Lianguo Chen, Jianshe Ma, Xianqin Wang, Meiling Zhang
Abstract
A specific ultraperformance liquid chromatography‐tandem mass spectrometry (UPLC‐MS/MS) method has been developed for the simultaneous determination of six Uncaria alkaloids in mouse blood with midazolam as the internal standard (IS). Only 20 μ L blood was needed for sample preparation, and the protein was precipitated with acetonitrile. The UPLC BEH C18 column (2.1 mm × 100 mm, 1.7 μ m) was used for chromatographic separation. The mobile phase consisted of 0.1% formic acid and acetonitrile with gradient elution within 5.5 min. Multiple reaction monitoring (MRM) and the positive electrospray ionization model were used for quantitative analysis. The accuracy of the UPLC‐MS/MS method ranged from 86.5% to 110.4%. The precision for intraday and interday was ≤15% each. The mean recovery and the matrix effects were found to be 64.4‐86.8% and 94.1‐109.4%, respectively. The calibration curves in blood were linear in the range of 1‐1000 ng/mL with a favorable correlation coefficient ( r 2 ) of 0.995. The pharmacokinetic results showed that six Uncaria alkaloids metabolized rapidly in mice with a half‐life between 0.6 h and 4.4 h. The bioavailability of corynoxeine, isocorynoxeine, rhynchophylline, isorhynchophylline, hirsutine, and hirsuteine was 27.3%, 32.7%, 49.4%, 29.5%, 68.9%, and 51.0%, respectively, which showed satisfactory oral absorption of each alkaloid.