Abstract: Quercetin 3-O-D-glucuronide (Q3G) is a natural flavonoids, and exhibits various biological activities like anti-inflammatory, hypoglycemic, and antioxidant ability. α-Lactalbumin（α-La) is an important component involved in nonenzymatic glycosylation of whey protein during storage and processing. In this study, α-lactalbumin (α-La)-fructose system was used as the glycosylation model, effect of Q3G on the formation of fructosamine and 5-hydroxymethylfurfural (5-HMF), as well as free amino acids contents and browning degree during non-enzymatic glycosylation were evaluated. Further, the inhibition mechanism was explored by molecular docking and mass spectrometry techniques. The results indicated that Q3G could significantly reduce the browning degree and increase the content of free amino acids, inhibit the formation of fructosamine and 5-HMF, delay the process of glycosylation reaction, and the addition of 2 mM Q3G displayed the strongest activitiy. Molecular docking analysis indicated that Q3G could bind with the active amino acids of α-La through hydrogen bond, van der Waals force and hydrophobic interactions, then influencing the reaction between protein and fructose, thus inhibiting the formation of glycosylation products and alleviating the process of glycosylation reaction. Meanwhile LC Orbitrap MS / MS analysis also found that Q3G screened the potential glycosylation active sites Lys93 and Lys108, and the activity of increased glycosylation site Lys98 was weak, resulting to depress non enzymatic glycosylation reaction. This study can provide a theoretical basis for the development of Q3G as a potential antiglycosylation agent.

Key words: Quercetin-3-O-glucoside, α-Lactalbumin, Molecular docking, LC-Orbitrap-MS/MS, Nonenzymatic glycosylation