Characterization of flavonol mono-, di-, tri- and tetra-O-glycosides by ultra-performance liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry and its application for identification of flavonol glycosides in Viola tianschanica.

In this study, 21 flavonol O-glycoside standards including flavonol mono-, di-, tri- and tetra-O-glycosides have been systematically studied by ultra-high performance liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS/MS) in the negative ionization mode to analyze their fragmentation patterns. Here for the first time, the Z fragment (corresponding to the loss of C-2" terminal sugar moiety) was observed in MS/MS spectra of flavonol 3-O-triglycosides. The intensity ratio of [Y-H]/Y was proposed as a criterion to distinguish the interglycosidic 1→2 and 1→6 linkages in flavonol 3-O-diglycosyl-7-O-monoglycosides. The established fragmentation behaviors have been successfully applied to characterization of flavonol glycosides in Viola tianschanica. A total of 30 flavonoid glycosides including 3 flavonol mono-O-glycosides, 10 di-O-glycosides, 10 tri-O-glycosides, 4 tetra-O-glycosides and 3 flavone di-C-glycosides were identified or tentatively identified on the base of their UV profiles, MS/MS data and/or by comparing with reference substances. Among these 15 flavonoid glycosides were reported from V. tianschanica for the first time.