In neutral solutions, desferrioxamine (Desferal) can react with the superoxide free radical, O2.- (possibly through its protonated form HO2.), to form a relatively stable nitroxide free radical, which can have a half-life of approx. 10 min at room temperature. The formation of the radical can be largely prevented by the presence of superoxide dismutase. The radical reacts rapidly with cysteine, methionine, glutathione, vitamin C and a water-soluble derivative of vitamin E. It also reacts rapidly with alcohol dehydrogenase, causing a loss of enzyme activity. The implications of these findings for mechanistic free-radical biochemistry and iron-chelation therapy could be considerable.