Abstract
Flavonoid glycosides are formed by dehydration condensation of aglycones and sugar molecules. Therefore, discrimination of flavonoid glycosides from their corresponding aglycones is a challenging task because they contain the same aglycone part in their molecular structures. Herein, boric acid-functional Eu(III)-organic framework (BA-Eu-MOF) was applied to discriminate flavonoid glycosides including baicalin (Bai), wogonoside (Wog), rutin (Rut), puerarin (Pue), quercitrin (Que) and astragalin (Ast) from their corresponding aglycones for the first time. Besides as organic ligand to sensitize the luminescence of Eu3+ through "antenna" effect, 5-boronobenzene-1,3 dicarboxylic acid provided recognition site for flavonoid glycosides. Infrared, fluorescence, UV-vis, and mass spectra were used to investigate the recognition reaction between BA-Eu-MOF and flavonoid glycosides. The data indicated that the cis-diols of flavonoid glycosides from sugars covalently bonded to boric acid group to form cyclic boronic esters, which quenched the fluorescence of BA-Eu-MOF at 620nm through decreasing the intersystem efficiency, inner filter effect and photoelectron transfer. In contrast, aglycones could not alter the fluorescence of BA-Eu-MOF because of no covalent bond between them. This probe exhibited high sensitivity towards flavonoid glycosides with the low detection limits of 3.3nM, 3.5nM, 33nM, 56nM, 5.1nM and 5.5nM for Bai, Que, Wog, Ast, Pue and Rut, respectively. The unique recognition ability of boric acid group enables selective and sensitive detection of flavonoid glycosides without the interference of their corresponding aglycones.
Published Version
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