Removal of polyphenols from anthocyanin-rich extracts using 4-vinylpyridine crosslinked copolymers

In this work, new sorbents for the purification of anthocyanin-rich extracts were evaluated. Copolymers of 4-vinylpyridine crosslinked with trimethylolpropane trimethacrylate (poly(4VP-co-TRIM)) or 1,4-dimethacryloyloxybenzene (poly(4VP-co-14DMB)) were tested for their potential to capture polyphenols. Copolymers were obtained by seed swelling polymerization in the form of microspheres with permanent porous structure - attractive features of sorbents used for sample purification by dispersive solid phase extraction. The microspheres were characterized by AFM, elemental analysis, SEM, and nitrogen adsorption-desorption method. Their capacity to remove polyphenols was evaluated using spectrophotometry, HPLC-DAD, and LC-MS/MS. For proof-of-concept, the aqueous extracts of berries classified into three different groups regarding their anthocyanin composition (strawberries, raspberries, blackcurrants) were selected. It was found that studied microspheres adsorbed flavonoids more effectively compared to primary secondary amine and graphitized carbon black. Copolymers of 4-vinylpyridine also capture anthocyanins and might be used for the purification of extracts of fruits before LC-MS/MS analysis to reduce the matrix effect.