Antioxidant activity of Ferrozine-iron-amino acid complexes

Amino acid-fe(II)-chelator complexes exhibit strong antioxidant activity. T aking advantage of the unique spectral characteristics of the complexes for med when Ferrozine (Fz) is used as the chelator, we now show that the prima ry blue complex (epsilon (max) at 632 nm) decomposes by two independent pat hways: (i) a nonoxidative pathway involving dissociation of the amino add c omponent and formation of a purple complex (epsilon (max) at 562 nm) and (i i) an oxidative pathway leading to Fe(lll) and colorless products. Quantita tive conversion of the blue to purple complex yields an isosbestic point (i .p.) at 601 nm, whereas no i.p. is formed during quantitative oxidation of the blue complex. However, under some experimental conditions, decompositio n of the blue product occurs by both pathways, leading to occurrence of a c lean i.p. at wavelengths varying from 601 to 574 nm. Results of simulation experiments, confirmed by direct analysis, demonstrate that shifts in the i .p. reflect differences in the fractions of blue compound that decompose by the oxidative and nonoxidative pathways. Indeed, the fraction of blue that is converted to the purple complex is readily deduced from the wavelength of the i.p. These results suggest that identification of a physiological ch elator that can replace Ferrozine in amino acid-iron complexes might have i mportant physiological and pharmacological applications.