Non-covalent interaction of Millettia specisoa protein and quercetin: Mechanism and physicochemical property

Protein and plant polyphenols are vital components of the food system, and their interactions have been extensively studied. Understanding these interactions is crucial for rationalizing functional foods and enhancing the bioavailability of both polyphenols and proteins. This study aimed to explore the non-covalent interactions between Millettia specisoa protein and quercetin, as well as the resulting changes in protein conformation. The results indicated that after non-covalent modification with quercetin significantly increased protein particle size, ζ-potential, antioxidant activity, bioaccessibility, and polyphenol binding equivalent, leading to protein aggregation. The analysis of Fourier transform infrared spectroscopy, circular dichroism, and fluorescence spectroscopy revealed that the conformation of protein underwent significant changes following its interaction with quercetin, especially as the concentration of quercetin increased, the random coil of the protein also increased, suggesting that the protein became more loose and disordered. Additionally, the thermodynamic analysis also demonstrated that hydrophobic interactions and hydrogen bonding were the primary forces between Millettia specisoa protein and quercetin.