A pulse radiolysis study of one-electron oxidation and .OH radical reaction of a new class of antioxidants: 2,5 dimethylpyrrole--amino acid N-conjugates.

A new class of 2,5 dimethylpyrrole functionalized amino acid and peptide antioxidants has been synthesized. Pulse radiolysis studies have been carried out on these compounds to determine their reactivity in one-electron oxidation reactions with Br2- and (SCN)2-, as well as their reactivity toward the water radicals .OH and eaq-. When compared to similar reactions with parent amino acids and peptides, both rate constants and transient spectra indicate considerable interaction between the electronic states of the pyrrole moiety and amino acid or peptide. Where comparison data is available, radical reactions are significantly more rapid with these derivatives than with the parent compounds. Exceptions occur in some cases of .OH attack where steric hindrance may be evoked to explain a lower rate constant in the derivative compounds. Electron attachment rates are also found to be enhanced by the presence of the pyrrole ring.