Superoxide-dependent formation of hydroxyl radicals: Detection of hydroxyl radicals by the hydroxylation of aromatic compounds

A mixture of xanthine or hypoxanthine and xanthine oxidase generates the superoxide radical, O₂^$\text{?}$, and H₂O₂. In the presence of iron salts, O₂^$\text{?}$ and H₂O₂ can interact to produce the hydroxyl radical, OH·. Superoxide-dependent formation of OH· can be measured by its ability to hydroxylate salicylate as followed by an improved colorimetric assay described in this paper. A more accurate analysis of OH· can be obtained using its ability to hydroxylate phenol, the hydroxylated products being separated and measured after derivatization using gas-liquid chromatography and electron-capture detection. The derivatization and separation techniques are described.