Oxidative damage of biomolecules associated with aging and age-related diseases is a complex function of antioxidant and prooxidant activities. Ternary complexes formed by the interaction of amino acids, chelating agents, and transition metal ions have been shown to exhibit antioxidant (catalase-like) activity and to protect cultured cells from damage upon exposure to oxidative stress. In an effort to understand the chemical mechanisms involved in the antioxidant activity of such complexes, we have taken advantage of the unique spectral characteristics of the complexes formed between ferrous iron, amino acids, and the iron chelator, ferrozine. When ferrous iron is added to reaction mixtures containing ferrozine and an amino acid, the primary product formed is a blue complex comprised of two equivalents of ferrozine, two equivalents of amino acid, and one equivalent of iron. Depending upon the relative concentrations of the three reactants, the blue complex may either undergo (i) slow oxidation by oxygen or rapid (almost instantaneous) oxidation by hydrogen peroxide to form ferric iron and other colorless as yet unidentified products, or (ii) may react with another molecule of ferrozine to regenerate the amino acid and form a purple complex of three equivalents of ferrozine and one equivalent of ferrous iron. - antioxidants, iron-amino acid complex, ferrozine