Identification, molecular docking and quantum chemical calculation study of novel antioxidant peptides from protein hydrolysate of defatted walnut (Juglans regia L.)

Nano-liquid chromatography–mass spectrometry was performed to identify the structures of the antioxidant peptides from walnut ( Juglans regia L.) protein hydrolysates, following which 15 hydrophobic and structurally stable antioxidant peptides were screened using computer-aided tools. The conformational relations of the antioxidant peptides were analyzed via molecular docking and quantum chemical calculations, and the activities of the peptides were verified using in vitro free radical scavenging experiments. Fifteen peptides were screened using computer simulation activity scores, among which GVLIPDQGIALRGLF, LSGPNSIIGR, ISVNDPFVMKA, QIPLSGPNSIIGRA and SQIPLGGPNAVIGRA showed the best antioxidant activities. Five antioxidant peptides were tightly bonded to the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) molecules by hydrogen bonding and hydrophobic interactions and possessed a strong free radical scavenging activity. The frontier molecular orbitals (HOMO) predicted active sites: Five antioxidant peptides interacted with bonds with the Asp, Arg, Leu, Ser, Ala, Gln, further, GVLIPDQGIALRGLF exhibiting the smallest the ΔE L–H (-3.432), correspondingly, with GVLIPDQGIALRGLF exhibiting the strongest antioxidant activity. The prediction results of the Fukui function active site for the five antioxidant peptides were consistent with the structure predicted by the energy levels of the front molecular orbitals. • Fraction with molecular weight <1 kDa had higher antioxidant effects. • 5632 peptides were identified from fraction with molecular weight <1 kDa. • Five novel antioxidant peptides were identified by in vitro and in silico. • The potential mechanism of antioxidant was studied by molecular docking. • Antioxidant peptides were analyzed using quantum chemistry.