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

摘要

Summary Tyr-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.