Abstract
Polyphenols have found a lot of therapeutic effects and potential applications such as antioxidant, anti-inflammatory, mutant resistance, immunosuppressant and anti-tumor properties. They can be divided into five main classes, namely flavonoids, phenolic acids, stilbenes, lignans, and others. Thus, the content detection of polyphenols in real samples such as fruit juice and tea is of great significance. Due to the presence of complex interfering components in actual samples, separation and enrichment of polyphenols prior to analysis is key. Therefore, it is quite necessary to establish a simple, low-cost and efficient purification method for cis-diol-containing polyphenols from real samples. Boronate affinity materials are able to reversibly bind cis-diol-containing compounds by forming a five- or six-membered boronic cyclic ester in aqueous media. However, conventional boronate affinity materials exhibited low binding capacity and high binding pH. In this study, the polyethyleneimine (PEI)-assisted 6-aminopyridine-3-boronic acid functionalized magnetic nanoparticles (MNPs) were developed to capture efficiently cis-diol-containing polyphenols under neutral condition. PEI was applied as a scaffold to amplify the number of boronic acid moieties. While 6-aminopyridine-3-boronic acid was used as an affinity ligand due to low pKa value and excellent water solubility toward polyphenols. The results indicated that the prepared boronic acid-functionalized MNPs provided high binding capacity and fast binding kinetics under neutral conditions. In addition, the obtained MNPs exhibited relatively high binding affinity (Kd ≈ 10−4 M), low binding pH (pH ≥ 6.0) and tolerance of the interference of abundant sugars.
Highlights
Polyphenols are a class of important compounds naturally present in plants including vegetables, fruits and teas
6aminopyridine-3-boronic acid had been used as affinity ligands to prepare boronic acid functionalized magnetic nanoparticles (MNPs),[40] PEI was not applied in this reference, which would affect the binding properties to some extent
300 mL solutions at different concentrations of caffeic acid (CA) were added to the above Fe3O4@PEI@PYBA suspension of 200 mL and shaken on a rotator for 1 h at room temperature
Summary
Polyphenols are a class of important compounds naturally present in plants including vegetables, fruits and teas. 6aminopyridine-3-boronic acid had been used as affinity ligands to prepare boronic acid functionalized MNPs,[40] PEI was not applied in this reference, which would affect the binding properties to some extent This is rst report on boronic acid functionalized materials using polyphenols as the research targets. We applied 6-aminopyridine-3-boronic acid and PEI as affinity ligands and a scaffold to prepare PEI-assisted 6aminopyridine-3-boronic acid-functionalized MNPs for highly efficient capture of cis-diol-containing polyphenols under neutral condition. A er washing, the MNPs were eluted in 100 mL acetic acid solution for 1 h on a rotator and the eluates were collected The eluent containing these polyphenols adsorbed by the Fe3O4@PEI@PYBA were measured with UV-vis spectrophotometer. The values for Kd and Qmax are evaluated based on the slope and the intercept of plots of Qe/Cs versus Qe
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