The Colorimetric Detection of the Hydroxyl Radical.

An aromatic substrate for hydroxylation by hydroxyl radicals ( ^• OH) was investigated. The probe, N,N '-(5-nitro-1,3-phenylene)- bis -glutaramide, and its hydroxylated product do not bind either iron(III) or iron(II), and so they do not interfere with the Fenton reaction. A spectrophotometric assay based on the hydroxylation of the substrate was developed. The synthesis and purification methods of this probe from previously published methodologies were improved upon, as well as the analytical procedure for monitoring the Fenton reaction through its use, enabling univocal and sensitive ^• OH detection. The assay was utilised to demonstrate that the iron(III) complexes of long-chain fatty acids lack Fenton activity under biological conditions.