Isomeric quantification of O-diglycosyl flavonoids by a complex-free kinetic method using ESI/QToF mass spectrometry

The complex-free kinetic method (CFKM), a novel variant of the kinetic method, was developed for direct quantification of isomeric O-diglycosyl flavonoids using electrospray ionization tandem mass spectrometry. Direct isomeric quantification of O-diglycosyl flavonoids by the developed CFKM was presented for the first time. The detailed fragmentation behaviours of these flavonoids, which are tightly related to their structures, were also proposed with the help of molecular modelling. The calibration curves enable the quantification of these isomeric pairs by the linear relationship of lnR vs. molar fractions of hesperidin and eriocitrin with good accuracy and good correlation coefficient(r2). High isomeric selectivity was achieved with Riso = 6.5349 and Riso = 3.5257 for hesperidin/neohesperidin and eriocitrin/neoeriocitrin, respectively by our developed CFKM. The CFKM represents a promising and practical mass spectrometric method for direct stereochemical analysis of flavonoid compounds as well as other multiple chiral center compounds.