Determination of andrograpolide sodium bisulphite in Beagle dog plasma by LC-MS/MS and its application to pharmacokinetics.

A sensitive and reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed and validated for the determination of andrographolide sodium bisulphite (ASB) in dog plasma using dehydroandrographolide (DAG) as an internal standard. Chromatographic separation was achieved on a Hypersil Gold C(18) column (50 mm × 2.1 mm, 1.9 μm) with gradient elution that consisted of methanol and water at a flow rate of 0.2 mL/min. Quantification was done using selected reaction monitoring (SRM) mode to monitor precursor-product ion transitions of m/z 413.2→287.2 for ASB and 331.2→303.3 for DAG at negative ionization mode. Good linearity was obtained over the range of 10-1000 ng/mL and the correlation coefficient was better than 0.99. The intra- and inter-day accuracies ranged from 97.2% to 107.8% and precisions (RSD) were within 13.9%. ASB was found stable under three freeze-thaw cycles, short-term temperature, post-preparative and long-term temperature conditions. The method was successfully applied to a pharmacokinetic study of ASB intravenously administered to Beagle dogs.