Photogeneration of superoxide by adriamycin and daunomycin

Abstract
The hydroxyl and superoxide anion spin adducts of DMPO and 4‐MePyBN, respectively, were obtained during photoirradiation of adriamycin and daunomycin solutions with visible light. Ethanol and dimethyl sulfoxide did not scavenge hydroxyl radicals in the photoirradiated drug solutions. Furthermore, the hydroxyl‐DMPO spin adduct is not formed in the photolysis of air‐free drug solutions, indicating that hydroxyl radicals are not directly produced in the photochemical reactions. Instead, the observed hydroxyl‐DMPO is formed from the decay of the superoxide anion‐DMPO spin adduct. The mechanism for generating the superoxide anion radical appears to be a direct electron transfer from the photoexcited adriamycin and daunomycin to dissolved oxygen.