D-galactose enhances Maillard reaction and antioxidant activity of arginine-derived products: experimental and molecular insights.

BACKGROUND: Arginine-derived Maillard reaction products (MRPs) have shown promising antioxidant activities. However, how structurally distinct hexose reducing sugars, such as D-fructose and D-galactose, affect the formation and functional properties of L-arginine-derived MRPs remains unclear. METHODS: Arginine-fructose (Arg-Fru) and arginine-galactose (Arg-Gal) model MRPs were prepared by heating at 100 °C for 0.5, 1, and 2 h. The reaction rate was analyzed by monitoring the reaction process and using a kinetic model, while substrate consumption and apparent melanoidin production were measured. Early non-covalent interactions were further investigated using molecular docking and 200 ns molecular dynamics (MD) simulations. Finally, functional differences were evaluated by chemical and intracellular antioxidant activities. RESULTS: Compared with Arg-Fru, Arg-Gal showed a more great decrease in pH and higher A294 and A420 values under the same reaction conditions. Kinetic analysis showed that Arg-Gal had higher reaction rate constants. Meanwhile, Arg-Gal exhibited stronger UV-Vis absorption and fluorescence intensity, greater consumption of free amino groups and reducing sugars, and higher apparent melanoidin formation. Molecular docking results showed that D-galactose formed more hydrogen bonds with L-arginine than D-fructose; MD simulations further showed that the Arg-Gal system formed approximately 20 more hydrogen bonds on average, and the diffusion behavior of D-galactose was closer to that of L-arginine, suggesting stronger non-covalent association. Functionally, Arg-Gal showed stronger DPPH radical scavenging capacity, reducing power, and intracellular antioxidant activity than Arg-Fru. CONCLUSION: D-galactose may promote the Maillard reaction process by enhancing early non-covalent interactions with L-arginine and being associated with enhanced formation of intermediates and melanoidin-related substances, thereby enhancing the antioxidant activity of MRPs. These findings provide experimental and molecular insights into the role of sugar structure in modulating arginine-derived Maillard reaction systems.