Targeted identification of glycosylated flavones and isomers in green tea through integrated ion-filtering strategy and mass-fragmentation characteristics based on the UPLC–Q–Orbitrap–MS/MS platform

Glycosylated flavones (GFs) are important components of green tea and have various structures and isomers. The annotation of GFs' chemical structures is challenging. Ultrahigh-performance liquid chromatography-high resolution mass spectrometry can provide informative mass ions for GF annotation. However, distinguishing the mass features of GFs from those of thousands of ions is difficult. In this study, integrated ion-filtering strategies for O- and C-glycosyl flavones were constructed, and the mass-fragmentation characteristics were summarized from GF standards. Ultimately, 29 GFs with different types of aglycones and glycosides, connection modes, and locations were annotated. According to principal component analysis and t-test results, significant differences were observed in the contents of 16 components in the two kinds of tea. Among them, the contents of 11 GFs in autumn teas were significantly higher than those in spring teas. This study provided an efficient strategy for isomer annotation in food analysis.