Interaction between pH-shifted β-conglycinin and flavonoids hesperetin/hesperidin: Characterization of nanocomplexes and binding mechanism

This study characterized the nanoparticles and the binding mechanism between pH-shifted soy β-conglycinin (β-CG) and hesperetin (Ht)/hesperidin (Hd). Different structural characteristics and concentrations of Ht/Hd were found to affect the encapsulation efficiency, loading amount, and particle size of pH-shifted β-CG‒Ht/Hd nanoparticles. This was the result of two glycosyl substituents (7-position of the C-ring) in the presence of Hd containing six hydroxyl groups interacting with the polar groups of proteins to form hydrogen bonds, which facilitated the formation of nanocomplexes. Besides, the exposed hydrophobic groups in the β-CG proteins resulting from pH shift treatment developed hydrophobic interactions with the benzene ring or glucoside in the flavonoids. Moreover, Ht/Hd strongly quenched the fluorescence of pH-shifted β-CG in static mode. After binding with flavonoids, the tertiary and secondary structures of pH-shifted β-CG were significantly changed. The finding presented in this study provided evidence of the binding mechanism of soy proteins and different structural flavonoids and will aid in the design of soy protein/flavonoid enriched-food.