Gamma and Pulse Radiolysis Investigation of the Reaction of Desferrioxamine with Superoxide Anions

Summary

The kinetic scheme of the reaction of desferrioxamine (DFO) with O₂ was studied using pulse and γ-radiolysis. The rate constant k(O₂ + DFO) is equal to 1·3 ± 0·1 × 10⁶ dm³ mol⁻¹ s⁻¹ at pH 7·4. Studying the competition between DFO and ferricytochrome-c for O₂ generated by γ-radiolysis, we observed that the nitroxide free radical resulting from the reaction of O₂ with DFO and the product(s) resulting from the decay of this nitroxide radical act inversely towards the cytochrome-c-Fe³⁺/cytochrome-c-Fe²⁺ redox couple. This explains the discrepancy between our value of k(O₂ + DFO) and the one measured previously using ferricytochrome-c for the detection of O₂. The reported results show that DFO acts as a powerful O₂ scavenger, and that the products resulting from the reaction of DFO with O₂ can initiate oxidative and/or reductive reactions that should be taken into account in interpreting the effects of DFO in vitro and in vivo.