Study on the interaction mechanism and physicochemical properties of luteolin and its glucoside compounds with β-lactoglobulin

Molecular docking simulations and multispectral approaches were used to study the non-covalent interactions between β-lactoglobulin (β-LG) and chosen luteolin (Lu), isoorientin (Iso), and cynaroside (Cyn). The fluorescence quenching results demonstrated that Lu, Iso, and Cyn spontaneously formed stable complexes with β-LG through static quenching. Thermodynamic parameters and molecular docking simulations demonstrated that hydrogen bonds were the primary forces driving the interactions between the protein and flavonoids. The binding constants followed the order: β-LG-Lu (2.87 × 10⁴ L/mol) > β-LG-Iso (1.83 × 10⁴ L/mol) > β-LG-Cyn (1.52 × 10⁴ L/mol). Additionally, the C-glycosylated flavonoid (Iso) showed a higher propensity to form hydrogen bonds with β-LG compared to the O-glycosylated flavonoid (Cyn). The results of circular dichroism indicated that the β-LG structure became looser with the introduction of Lu, Iso, and Cyn. Furthermore, the assembly of β-LG-flavonoid complexes decreased the surface hydrophobicity and oil-water interfacial tension of β-LG, improved its foaming and emulsifying capabilities, and protected the antioxidant properties of the flavonoids to a certain extent. This study investigated the interaction mechanisms between flavonoids with different glycosyl types and β-LG, providing insights for the incorporation of suitable flavonoids into dairy products, and offering theoretical perspectives on preserving the antioxidant properties of flavonoids.