Simultaneous LC−MS/MS determination of five tripterygium pyridine alkaloids in dog plasma and its application to their pharmacokinetic study after oral administration of tripterygium glycosides tablets

• A method to estimate five tripterygium pyridine alkaloids in plasma was developed.
• The LLOQs were as low as 0.2 ng/mL for triptolide and 0.05 ng/mL for four alkaloids.
• The pharmacokinetic parameters of five ingredients in dog were reported firstly.

A sensitive and selective liquid chromatography tandem mass spectrometric method was developed and validated for the simultaneous determination of five pyridine alkaloids contained in tripterygium glycosides tablets (triptolide, wilforine, wilforgine, wilfording and wilfortrine) in dog plasma. The analysis was carried out on a Sepax GP-Phenyl column using a mixture of methanol and 10 mmol/L ammonium formate buffer solution containing 0.1% formic acid (75:25, v/v) as the mobile phase pumped at a flow-rate of 1.0 mL/min. All MS data were obtained in the positive ESI mode with selective multiple reaction monitoring of ion transitions. The method was fully validated to be accurate and precise with a linear range of 0.2–1000 ng/mL for triptolide and 0.05–1000 ng/mL for the other four pyridine alkaloids. The intra-day and inter-day precisions (relative standard deviation, RSD, %) were within 10.6% and 14.0%, respectively, and the relative error (RE, %) were all less than 13.1%. The method was successfully applied to multi-components pharmacokinetic study of the five pyridine alkaloids in beagle dogs after a single oral administration of 3 mg/kg and 30 mg/kg tripterygium glycosides tablets, respectively, and a multiple oral administration of 30 mg/kg for 6 consecutive days.