A HPLC–MS/MS method for the simultaneous quantitation of six alkaloids of Rhizoma Corydalis Decumbentis in rat plasma and its application to a pharmacokinetic study

A specific and reliable HPLC–MS/MS method was developed and validated for the simultaneous determination of six alkaloids in rat plasma, jatrorrhizine, berberine, tetrahydropalmatine, protopine, bicuculline and palmatine. The analytes were separated on a C18 column (50 mm × 2.1 mm, 1.8 μm) and a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source was used for detection. The plasma sample was prepared by the simple protein precipitation and the recovery for the six analytes was over 80%. The calibration curves were linear over a concentration range of 0.38–1900.0 ng/mL for jatrorrhizine, 0.57–2850.0 ng/mL for berberine, 0.32–1600.0 ng/mL for tetrahydropalmatine, 0.21–1050.0 ng/mL for protopine, 0.34–1700.0 ng/mL for bicuculline and 0.22–1100 ng/mL for palmatine. The intra-day and inter-day precision was less than 15% and the relative error (RE) was all within ±15%. The validated method was successfully applied to a pharmacokinetics study in rats after oral administration of the extracts of Rhizoma Corydalis Decumbentis (a famous Chinese herb).