Cytoprotective effect and purification of novel antioxidant peptides from hazelnut (C. heterophylla Fisch) protein hydrolysates

•Antioxidant fraction C2 showed cytoprotective effect against Ang II induced oxidative stress damage in HUVECs.•Six novel antioxidant peptides were identified from hazelnut protein hydrolysates.•Hydrophobic amino acid was crucial to antioxidant capacity. In the present study, antioxidant fraction (C2) has been obtained from a hazelnut processing by-product. The C2 exhibited strong antioxidant and cytoprotective effect against Ang II induced oxidant injury via up-regulation of SOD and heme oxygenase-1 (HO-1) levels and down-regulation of xanthine oxidase-1 (XO-1) level to inhibit the production of ROS synthesis in human umbilical vein endothelial cells (HUVECs). LC-ESI-MS/MS results revealed that C2 was found to include six novel peptides and their amino acid sequences were ADGF (408.16 Da), AGGF (350.16 Da), AWDPE (616.25 Da), DWDPK (659.29 Da), ETTL (462.23 Da), and SGAF (380.17 Da). All six synthetic peptides showed excellent antioxidant activity. Especially, the ADGF peptide exhibited the highest ABTS radical scavenging activity and DPPH radical scavenging ability among them. Therefore, the peptides isolated from wild hazelnut protein hydrolysates may be used as potential antioxidants in the food and drug industries.