Pharmacokinetic analysis of levo-tetrahydropalmatine in rabbit plasma by rapid sample preparation and liquid chromatography-tandem mass spectrometry.

A rapid extraction method was developed and validated for levo-tetrahydropalmatine (l-THP) determination in rabbit plasma by liquid chromatography tandem-mass spectrometry (LC-MS/MS). The sample preparation included a single-step acetonitrile extraction and salting out liquid-liquid partitioning from the water in plasma with MgSO4. Berberine was used as internal standard. The mass spectrometry source was negative electrospray ionization. The method showed good performance in the concentration range from 5 to 200ngmL(-1). The limit of quantification (LOQ) was 1ngmL(-1). The method was successfully applied to a pharmacokinetic study in rabbit comparing the two drug formulation of l-THP including the raw material and the self-microemulsifying drug delivery system pellet.