Pro-oxidant activity of aluminum: Promoting the Fenton reaction by reducing Fe(III) to Fe(II)

The possibility for an Al-superoxide complex to reduce Fe(III) to Fe(II), promoting oxidative damage through the Fenton reaction, is investigated using highly accurate ab initio methods and density functional theory in conjunction with solvation continuum methods to simulate bulk solvent effects. It is found that the redox reaction between Al-superoxide and Fe(III) to produce Fe(II) is exothermic. Moreover, the loss of an electron from the superoxide radical ion in the Al-superoxide complex leads to a spontaneous dissociation of molecular oxygen from aluminum, recovering therefore an Al3+ hexahydrated complex. As demonstrated in previous studies, this complex is again prone to stabilize another superoxide molecule, suggesting a catalytic cycle that augments the concentration of Fe(II) in the presence of Al(III). Similar results are found for Al(OH)2+ and Al(OH)2+ hydrolytic species. Our work reinforces the idea that the presence of aluminum in biological systems could lead to an important pro-oxidant activity through a superoxide formation mechanism.

Graphical abstractA theoretical study of the favorable redox reaction between Al-superoxide complex and Fe(III) is presented. The results may help in the explanation of the experimentally observed pro-oxidant activity of aluminum and the enhanced redox activity of iron in the presence of aluminum.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Theoretical study of the redox reaction between Al-superoxide and Fe(III). ► We found favorable redox reactions which suggest a Fenton cycle catalized by Al. ► Presented data may help in the explanation of observed pro-oxidant activity of Al. ► Contribution of ab initio calculations to the knowledge of toxicity of Al.