Structure-activity relationship of antioxidant peptides derived from the gastrointestinal digestion of amaranth proteins

PAULINO, MARGOT ; NARDO AGUSTINA E.; GARCIA FILLERIA, SUSAN; TIRONI A. VALERIA

Campinas

Congreso; 1st Ibero-American Congress on Bioactive Peptides; 2019

Institute of Food Technology (Ital), Campinas, Brazil

Ten peptides generated from 11S globulin of amaranth seed by simulated gastrointestinal digestion: TEVWDSNEQ (P1), IYIEQGNGITGM (P2), GDRFQDQHQ (P3), LAGKPQQEHSGEHQ (P4), YLAGKPQQEH (P5), PLQAEQDDR (P6), PHVIKPPSRA (P7), AWEEREQGSR (P8), AVNVDDPSK (P9) and KFNRPETT (P10), were studied. The objective was to correlate in silico characterization with the possible mechanisms of antioxidant activity. Physicochemical properties (isoelectric point, charge, amino acid ratio and hydrophobicity/hydrophilicity ratio by Sequence Manipulation Suite server); peptide structure and properties derived from molecular dynamics simulations (MOE2015.1), and peptide-cell interaction properties (toxicity by ToxinPred, and cell penetration by CPPred) were analyzed. Antioxidant activities were evaluated in chemical in vitro systems against free radicals (ORAC and HORAC), in ex vivo assay (LDL oxidation induced by Cu+2/H2O2), and with cellular assay (ROS scavenging in Caco2-TC7 cells induced by H2O2). P8 (hydrophilic, high proportion of acidic amino acids), P5 (hydrophilic, aliphatics), P2 (hydrophobic, aliphatics) and P1 (hydrophilic, acids) had the greatest activity by both chemical in vitro methods; all presented negative or neutral charge and belonging to the acid subunit of 11S globulin. The three most active peptides in the prevention of the LDL oxidation were P3 (negative, hydrophilic and acid), P7 (positive, hydrophobic and aliphatic) and P10 (positive, hydrophilic and neutral). All peptides, except P8 and P9, decreased the intracellular ROS content, presenting P1, P2, P3 and P10 the greatest activities. P2, P3 and P4 presented greater surface area accessible to the solvent (water). None of the peptides showed in silico cytotoxicity or high probability of cell penetration. The lack of correlation between in vitro, ex vivo and cellular activities could be due to modifications suffered by the peptides in the presence of cells, the influence of peptides physic-chemical and structural properties on the interaction with complex systems (LDL/cells) or because the existence of mechanisms other than the direct neutralization of ROS.