Metabolic profiling and pharmacokinetic studies of sinapine thiocyanate by UHPLC-Q/TOF-MS and UHPLC-MS/MS.

Sinapine thiocyanate (ST) is an index component and pharmacological active component of Semen Sinapis and Semen Raphani, and it is widely used to relieving cough and asthma. This study aimed to obtain the metabolic and pharmacokinetic characterization of ST. The metabolic profiles of ST were obtained from rat plasma, urine, and feces via ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-Q/TOF-MS). Thirteen metabolites were structurally identified, and the proposed metabolic pathways of ST included deamination, demethylation, hydrogenation, dehydration, and extensive conjugation, including glucuronidation and sulfonation. ST was selected as the plasma marker for the pharmacokinetic study. A simple and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for the quantitation of ST in rat plasma. The linear range of ST was 0.1-500 ng/mL (R2 = 0.9976), and the lowest limit of quantification was 0.1 ng/mL. The intra-precision and inter-precision of the assay were 1.31-5.12% and 2.72-7.66%, and the accuracy (RE%) ranged from - 4.88% to 3.82% and - 3.47% to 6.18%. The extraction recovery, matrix effect, and stability of ST were within acceptable limits. The established method was validated and successfully applied to the pharmacokinetic study of ST. For pharmacokinetic experiments, the male Sprague-Dawley rats were administrated with ST solution intravenously (2 mg/kg) or orally (100 mg/kg). The oral absolute bioavailability of ST was calculated as 1.84%, and the apparent volume of distribution of intravenous and intragastric administrations were 107.51 ± 21.16 L/kg and 78.60 ± 14.44 L/kg, respectively. The maximum plasma concentration was 47.82 ± 18.77 nM, and the time to maximum peak was 88.74 ± 20.08 min for the intragastric dosing group. According to the pharmacokinetic and metabolic profiling results, metabolites with high abundance of ST in bio-fluids would be the next object in tissue distribution and pharmacodynamic study.