Novel antioxidant and cytoprotective peptides from Psophocarpus tetragonolobus (L.) DC seed protein hydrolysate

Psophocarpus tetragonolobus (L.) DC seed (PT) is rich in protein and holds potential as a valuable nutritional supplement. To explore its antioxidant properties, protein from the winged bean seed (PTP) was extracted and hydrolyzed with alcalase to produce a protein hydrolysate (PTPH). The antioxidant activity of PTPH was evaluated by measuring its 2,2′-diphenyl-1-picrylhydrazyl (DPPH) assay and 2,2-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical scavenging activities. It exhibited potent DPPH and ABTS scavenging activities, with IC₅₀ values of 2.10 ± 1.03 and 0.73 ± 2.01 µg/mL, respectively. PTPH demonstrated no toxicity toward L929 mouse fibroblast cells and was cytoprotective against H₂O₂-induced damage in L929 cells. At low concentrations, it even promoted cell proliferation. Using anion exchange chromatography and liquid chromatography-mass spectrometry/mass spectrometry (LC–MS/MS), ten peptides with molecular weights ranging from 707.35 to 1,478.80 Da were isolated and identified from PTPH. Three synthetic peptides (YGDPVKF, LSHTLFGDELCK, and YLYELAR) exhibited strong ABTS radical scavenging activity and protected L929 cells from H₂O₂-induced oxidative stress by reducing intracellular ROS levels. These findings suggest that the protein hydrolysate and peptides derived from PT seeds have potential applications as natural antioxidants in food supplements and health-related nutraceuticals.