Development of a validated UPLC-MS/MS method for determination of humantenmine in rat plasma and its application in pharmacokinetics and bioavailability studies.

Humantenmine (HMT), the most toxic compound isolated from Gelsemium elegans Benth, is a well-known active herbal compound. A rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated to estimate the absolute oral bioavailability of HMT in rats. Quantification was performed by multiple reaction monitoring using electrospray ionization operated in positive ion mode with transitions of m/z 327.14 → m/z 296.19 for HMT and m/z 323.20 → m/z 236.23 for gelsemine (internal standard, IS). The linear range of the calibration curve was 1-256 nmol/L, with a lower limit of quantification at 1 nmol/L. The accuracy of HMT ranged from 89.39 to 107.5%, and the precision was within 12.24% (RSD). Excellent recovery and negligible matrix effect were observed. HMT remained stable during storage, preparation and analytical procedures. The pharmacokinetics of HMT in rats showed that HMT reached the concentration peak at 12.50 ± 2.74 min with a peak concentration of 28.49 ± 6.65 nmol/L, and the corresponding area under the concentration-time curve (AUC0-t ) was 1142.42 ± 202.92 nmol/L min after 200 µg/kg HMT was orally administered to rats. The AUC0-t of HMT given at 20 µg/kg by tail vein administration was 1518.46 ± 192.24 nmol/L min. The calculated absolute bioavailability of HMT was 7.66%.