Structural Elucidation of in Vitro and in Vivo Metabolites of Emodin in Rats by LC -ESI-MS/MS

Abstract

Emodin is a widely occurring natural product and has been studied extensively for its varieties of pharmacological activity. In attempt to know more deeply about its metabolism, this paper investigated the metabolites of emodin in rats, including its in vitro conversion product by intestinal microflora and urinary metabolites. The detection of emodin metabolites was performed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) with negative ion mode. By comparing the changes of metabolites in molecular masses (∆M), product ions and retention times with those of the parent drug, six metabolites (8-O-methylemodin, ω-hydroxyemodin, x-hydroxyemodin, emodin glucuronide, hydroxyemodin glucuronide and emodin sulfate) were observed，and what is more, the metabolite hydroxyemodin glucuronide was first reported in this article. For some metabolites, identification of their precise structure needs to be confirmed by other techniques such as the ¹H and ¹³C NMR