Beyond antioxidant actions: Insights into the antioxidant activities of tyr‐containing dipeptides in aqueous solution systems and liposomal systems

Abstract

SummaryTyr‐containing dipeptides deserve close attention because of their interesting bioactivities. This study aimed to make a contribution to the antioxidant activity evaluation of these dipeptides, through examining the chemical reactions underlying the results obtained in ABTS, ORAC assays and liposomal systems. Among Tyr‐Tyr, Tyr‐Phe, Phe‐Tyr, Tyr‐Ala and Tyr‐Ser, Tyr‐Tyr displayed the highest activity in all methods. Compared with Tyr‐Phe, Phe‐Tyr exhibited a higher activity in ORAC assay but a lower activity in ABTS assay. In liposomal systems, significant differences were found among the dipeptides in antioxidant actions against lipid peroxidation initiated by water or lipid‐soluble radicals. Electron and/or hydrogen transfer were involved in the detected antioxidant actions, with the location of Tyr at the C‐/N‐terminus being a crucial factor. Besides the structural features of peptides, the characteristics of liposomes, location of lipid oxidation initiation and peptide distribution in/on liposomal membranes all influenced the outcome of antioxidant actions.