Relative Determination Approach to the Metabolites of Protoberberine Alkaloids in Rat Urine by Liquid Chromatography Tandem Mass Spectrometry for the Comparative Studies on Rhizome coptidis and Zuojinwan Preparation

The lack of authentic standards has limited the quantitative analysis of herbal drugs in biological samples. The present work demonstrated a practicable strategy for the assay of herbs and their metabolites independent 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 Rhizome coptidis and Zuojinwan preparation in rat urine has been developed. Urine samples, extracted with a protein precipitation procedure were separated on a C18 column using a mixture of water (containing 0.1% formic acid) and acetonitrile (30:70, v/v) as mobile phase. The detection was performed via 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 which was calibrated by authentic standards. The fully validated method was applied to the pharmacokinetic study of 2,9-demethyljateorhizine-3-sulfate, 13-methoxyjateorhizine-3- glucoronide and 6-methyljateorhizine-5-glucoronide in rat urine. The results could provide evidence to explain the combination of Rhizome coptidis and Evodiae fructus in terms of elimination.