Mechanism of Action of Quercetin-3-O-glucoside against the Non-enzymatic Glycosylation of α-Lactalbumin

In this study, the effect of quercetin-3-O-β-D-glucuronide (Q3G) on the formation of fructosamine and 5-hydroxymethylfurfural (5-HMF), the amount of free amino groups and browning degree in a non-enzymatic glycosylation model consisting of bovine α-lactalbumin (α-La) and fructose were evaluated. In addition, the inhibitory mechanism of Q3G against non-enzymatic glycosylation was explored by molecular docking and mass spectrometry (MS). The results indicated that Q3G could significantly reduce the browning degree, increase the free amino groups, inhibit the formation of fructosamine and 5-HMF, and delay the process of glycosylation reaction. The effect was most pronounced at 2 mmol/L Q3G. Molecular docking analysis indicated that Q3G could bind with the active amino acid residues of α-La through hydrogen bonds, van der Waals force and hydrophobic interactions, delaying the process of glycosylation reaction. Meanwhile, by ultra-high performance liquid chromatography-quadrupole-orbitrap tandem mass spectrometry (UPLC-Q-Orbitrap MS/MS) analysis, it was found that Q3G shielded the potential glycosylation sites Lys93 and Lys108, and the activity of the glycosylation site Lys98 was weak, indicating inhibited non-enzymatic glycosylation reaction. This study can provide a theoretical basis for the development of Q3G as a potential anti-glycosylation agent.