Effect of Ultrasound‐Induced the Structural Changes in Casein on α‐Glucosidase Inhibitory Peptide of Its Hydrolysate

ABSTRACT The effects of ultrasonic powers on casein structure and the α‐glucosidase inhibitory activity of casein hydrolysates were investigated. Potential α‐glucosidase inhibitory peptides generated from casein hydrolysate were identified by LC‐MS/MS and predicted by in silico. The action mechanism of the potential α‐glucosidase inhibitory peptides was further explored based on molecular docking. The results demonstrated that 300 W ultrasound treatment significantly enhanced fluorescence intensity and surface hydrophobicity ( P < 0.05), along with a decrease in particle size ( P < 0.05), an increase in zeta potential absolute value, and sulfhydryl contents ( P < 0.05) of casein. Concurrently, a significant decrease in α‐helix and β‐sheet content of casein was detected ( P < 0.05). Notably, the hydrolysate derived from 300 W ultrasound pretreatment casein exhibited a hydrolysis degree of 24.35% ± 1.28% and α‐glucosidase inhibitory activity of 57.43% ± 2.15%, both significantly higher than the untreated group ( P < 0.05). Three potential α‐glucosidase inhibitory peptides RYPSYGI, SRYPSYGLN, and YQKFPQYL displayed PeptideRanker scores above 0.5, low molecular weight, and were predicted to have good human intestinal absorption and be non‐toxic. Molecular docking revealed that binding energies with α‐glucosidase were −9.4, −8.6, and −7.4 kcal/mol, respectively. The identified peptides bound to amino acid residues within the active site of α‐glucosidase through hydrogen bonding, electrostatic interactions, and hydrophobic interactions. In conclusion, ultrasonic pretreatment‐assisted enzymolysis was an effective technique for preparing α‐glucosidase inhibitory peptides from casein.