Study of the characteristic fragmentation behavior of hydroquinone glycosides by electrospray ionization tandem mass spectrometry with optimization of collision energy.

The fragmentation behavior of hydroquinone glycosides involving one or two sugar groups from Fraxinus sieboldiana and their analogue arbutin was investigated systematically by electrospray ionization tandem mass spectrometry in negative ion mode. The characteristic fragmentation reaction of these compounds was through the homolytic and heterolytic cleavage of the O-glycosidic bond to produce radical aglycone ion ([Y0-H]-*) and aglycone ion (Y0-), respectively. Unambiguous differentiation between the mono-O-glycoside isomers which differ in glycosylation position was achieved by comparing the relative abundance of [Y0-H]-* and Y0- ions with the optimized collision energy. In the fragmentation of 1, 4-di-O-glycosides, only the Y0- ion was produced when the first glucosyl residue was expelled. However, both the [Y0-H]-* and Y0- ions were present when the second glucosyl residue was eliminated. In addition, an interesting [Y0-2H]- ion was present in the product ion spectra of hydroquinone glycosides with methoxy group(s) substituted at C-3 or/and C-5 positions of the benzene ring. The results of this study can facilitate the rapid determination of hydroquinone glycosides in crude plant extracts and also reveal that the systematic investigation and optimization of collision energy play an important role in the differentiation of isomers which have subtle differences in structures. Copyright 2009 John Wiley & Sons, Ltd.