Mitigation of ovalbumin glycation in vitro by its treatment with green tea polyphenols

Polyphenols are known as inhibitors of glycation since they alter the pathways of the Maillard reaction by several mechanisms involving antioxidant activity, reactive dicarbonyl trapping, inhibition of sugar autoxidation, and amino group binding. Green tea is a rich source of polyphenols. This study aimed to investigate the effects of protein modification with green tea polyphenols on glycation potential of ovalbumin. For this purpose, green tea infusion was prepared and ovalbumin was treated with that infusion at alkaline pH conditions in order to let oxidation of polyphenols to quinone forms and formation of covalent linkages between quinones and amine residues of protein. This modified ovalbumin was heated with glucose at 90 °C. Furosine, the compound formed from N-ε-fructoselysine during acid hydrolysis, and N-ε-carboxymethyl lysine (CML) as indicators of early and advanced glycation, respectively, were monitored. Free lysine concentrations and antioxidant activity were measured in order to enlighten the interaction mechanism. Results showed that treatment of ovalbumin with green tea phenolics before reaction with glucose has a potential to limit glycation. In total 15 % less furosine was formed in treated ovalbumin than control ovalbumin upon heating at 90 °C for 1 h, whereas 14 % less CML was formed.