FREE RADICALS FROM PHOTOREDUCTION OF HEMATOPORPHYRIN IN AQUEOUS SOLUTION

Abstract —The anaerobic photoreduction of hematoporphyrin by organic reducing agents in fluid aqueous solutions has been studied by electron spin resonance spectroscopy. Efficient photoreduction occurs with many hydrogen‐atom or electron donors, including catechols, pyrogallol. hydroquinone. ascorbate, p ‐phenylenediamine, cysteine and glutathione. A combination of direct and spin‐trapping measurements (using 2‐methyl‐2‐nitrosopropane) has been used to confirm production of radicals from both the porphyrin and the reducing agent in each system.