Mass spectrometric methods for the characterisation and differentiation of isomeric O-diglycosyl flavonoids.

Tandem mass spectrometric methods have been evaluated for the characterisation of the type and the differentiation of the interglycosidic linkage of isomeric flavonoid O-diglycosides. Based on the occurrence of internal monosaccharide residue loss and the relative abundances of Y-type ions formed by fragmentation at glycosidic bonds, four pairs of isomeric flavonoid O-diglycosides can be unambiguously differentiated. The different techniques used, i.e. linked scanning at constant B/E without collisional activation and low-energy collision-induced dissociation using methane or helium as collision gas, have been shown to be useful for distinguishing the two most common (1, 2- and 1, 6-) interglycosidic linkages, e.g. flavonoid O-neohesperidosides and O-rutinosides.