Characterization of emodin metabolites in Raji cells by LC-APCI-MS/MS

A rapid, simple, and sensitive liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS/MS) method was developed for the identification and quantification of emodin metabolites in Raji cells, using aloe-emodin as an internal standard. Analyses were performed on an LC system employing a Cosmosil 5C(18) AR-II column and a stepwise gradient elution with methanol-20mM ammonium formate at a flow rate of 1.0 mL/min operating in the negative ion mode. As a result, the starting material emodin and its five metabolites were detected by analyzing extracts of Raji cells that had been cultivated in the presence of emodin. The identification of the metabolites and elucidation of their structures were performed by comparing their retention times and spectral patterns with those of synthetic samples. In addition to the major metabolite 8-O-methylemodin, four other metabolites were assigned as omega-hydroxyemodin, 3-O-methyl-omega-hydroxyemodin, 3-O-methylemodin (physcion), and chrysophanol.