Preparation and identification of antioxidant peptides from Quasipaa spinosa skin through two-step enzymatic hydrolysis and molecular simulation

Frog skin, a by-product of Quasipaa Spinosa farming, is rich in protein and potentially a valuable raw material for obtaining antioxidant peptides. This study used papain combined with acid protease to digest frog skin in a two-step enzymatic hydrolysis method. Based on a single factor and response surface experiments, experimental conditions were optimized, and the degree of hydrolysis was 30 %. A frog skin hydrolysate (QSPH-Ⅰ-3) was obtained following ultrafiltration and gel filtration chromatography. IC50 for DPPH, ABTS, and hydroxyl radical scavenging capacities were 1.68 ± 0.05, 1.20 ± 0.14 and 1.55 ± 0.11 mg/mL, respectively. Peptide sequences (17) were analyzed and, through molecular docking, peptides with low binding energies for KEAP1 were identified, which might affect the NRF2-KEAP1 pathway. These findings suggest protein hydrolysates and antioxidant peptide derivatives might be used in functional foods.