Study of Electrochemical Oxidation of Xanthohumol by Ultra-Performance Liquid Chromatography Coupled to High Resolution Tandem Mass Spectrometry and Ion Mobility Mass Spectrometry

Electrochemically assisted oxidation off-line combined with UPLC/ESI–MS and ion mobility mass spectrometry enabled us to gain insight into the oxidation mechanisms of xanthohumol. Several types of monomeric oxidation products were identified, i.e., monohydroxylated and dehydrogenated derivatives and related quinones. Besides, high contents of dimers were observed. The structures of four main oxidative condensation products of two xanthohumol molecules were proposed based on combination of retention time, exact mass measurement, fragmentation pattern, data from on-line ion mobility mass spectrometric experiments and with the support of independent electrochemical experiments. To the best of our knowledge, this is the first evidence on formation of xanthohumol dimers. The effect of the pH on the generation of oxidation products was further investigated. The monomeric and dimeric oxidation products are favored at pH of 5.5 and 4.5, respectively.