Characterization and determination of the alkaloid metabolites of Evodiae fructus in rat urine by liquid chromatography-tandem mass spectrometry detection.

The lack of authentic standards limits the quantitative analysis of herbal drugs in biological samples. This present work demonstrated a practicable assay of herbs and their metabolites independent of the availability of authentic standards. A liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for the qualitative and quantitative determination of the metabolites after oral administration of Evodiae fructus and Zuojinwan preparation in rat urine has been developed. Urine samples extracted with a protein precipitation procedure were separated on a C(18) column using a mixture of water (containing 0.1% formic acid) and acetonitrile (30:70, v/v) as mobile phase. The detection was performed by MS with electrospray ionization interface in positive selected reaction monitoring (SRM) mode. One urine sample after administration was selected as 'standard'. The method validation was carried out according to a conventional method that was calibrated by authentic standards. The fully validated method was applied to the pharmacokinetic study of the metabolites in rat urine. The results could provide evidence to explain the combination of Coptidis rhizoma and Evodiae fructus in terms of elimination.