Purification, identification, and in silico screening of a multifunctional octapeptide from semen armeniacae glutelin-2 hydrolysates: restraining mechanisms to Keap1 and ACE, stability, and ferrous-transport efficiency

After Sephadex G-15 isolation, electrospray ionization mass spectrometry, and AHTpin and Peptide Ranker database screening, a safe multifunctional octapeptide: Pro-Val-Asp-Phe-Ala-Gly-Phe-Tyr (PVDFAGFY), was obtained. The capacities of PVDFAGFY to restrain ACE, chelate ferrous ions, and quench hydroxyl radical were IC₅₀:105.61 μmol/L, 11.67 mg/g, and 97.67%, respectively. PVDFAGFY restrained ACE via competitively linking to its catalytic (His383) and/or crucial binding sites (Gln281, Lys511, Tyr523, Tyr520, or Ala354), and it can inhibit the Keap1-Nrf2 interaction by binding to 6 residues of Keap1. Ferrous ions were primarily chelated by <i>γ</i>-hydroxyl, carboxyl, and/or amino groups of PVDFAGFY via ionic forces. Gastrointestinal hydrolysis did not decrease the capacity of PVDFAGFY to antioxidant and restrain ACE (<i>p</i> > 0.05). The ACE inhibition model and activity of PVDFAGFY were not altered by iron chelation; however, PVDFAGFY-ferrous chelate showed lower hydroxyl and ABTS radical quenching capacity and ferric reducing ability than PVDFAGFY (<i>p</i> < 0.05). The gastrointestinal stability and transmembrane absorption of ferrous ions were increased by PVDFAGFY (<i>p</i> < 0.05). Thus, PVDFAGFY may be exploited as ingredients of hypotensive, antioxidant, and/or iron supplementary agents, but <i>in vivo</i> antioxidant and hypotensive efficiencies need further study.