Peptides were designed based on the identified structural motif of the most potent antioxidant peptides derived from barley protein. Six peptides contained the effective pentapeptide QPYPQ with appended Gln and Pro residues and the other peptides possessed higher hydrophobicity. The peptides have the repetitive sequences of Q, P and Y to investigate the contribution of vicinal residues to their antioxidant capacity. Antioxidant activity of the synthetic peptides was evaluated in chemical and cellular models. Free radical scavenging assays demonstrated the positive role of QP and PY pairs in stabilizing the peptide radicals. Cellular models revealed that repetitive peptide sequences effectively inactivate lipid hydroperoxides and intracellular reactive oxygen species. Peptides with alternating residues were also found effective in inhibition of amyloid fibril formation. These results verified that in addition to the chemical structure of individual side chains, the combined effects of the vicinal residues are also important in antioxidant activity of the whole peptide.