Role of free radicals in the mode of action of anthralin.

Radical reactions of anthralin and its metabolites with skin have been studied by ESR spectroscopy. The influence of compounds which are known to suppress inflammation are described. The ESR spectra recorded during the reaction of anthralin with skin were essentially composed of one broad line centered at g = 2.0030. Similar but much weaker spectra were recorded with the dimer and no signal at all was obtained with 9,10-dihydroxyanthraquinone. The ESR response obtained with anthralin was neither affected by the radical scavengers 2-tert-butyl-4-methoxy-phenol (BHA), 2,6-di-tert-butyl-4-methyl-phenol (BHT) dl-alpha-tocopherol, nor by the antiinflammatory agents clobetasol-17-propionate or indomethacin, nor by potassium hydroxide. We infer that anthralin inflammation is not associated with the presence of anthralin-derived radicals in the skin.