Screening, identification, and mechanism of novel antioxidant peptides in walnut meal under aerobic stress.

Walnut (Juglans regia L.) meal, being the primary by-product of walnut oil processing, is rich in high-quality proteins and of significant potential for development and utilization. The study used multi-stage gradient purification, liquid-quantity chromatography, and computerized virtual screening to isolate and characterize antioxidant peptides from walnut meal. Active sites and mechanism actions of antioxidant peptides were examined using oxidative damage model of HepG2 cells. Five novel peptides exhibiting high antioxidant activity were identified, among which YR-10 significantly increased the cell viability of HepG2 oxidatively damaged cells to 20.64 %. Meanwhile, YR-10 significantly reduced the ROS content to 42.54 % and apoptosis level to 11.80 % in HepG2 oxidatively damaged cells. In addition, YR-10 competed with Nrf2 for Keap1 binding site, inhibited Keap1 (13.83 %) expression, and promoted Nrf2 (27.15 %), HO-1 (34.59 %), and SOD1 (42.67 %) expression, which ultimately activated the Keap1/Nrf2/HO-1 pathway and alleviated oxidative damage.