Photosensitization by antitumor agents 3: spectroscopic evidence for superoxide and hydroxyl radical production by anthrapyrazole-sensitized oxidation of nadh

EPR and spin-trapping techniques were employed to study the oxidation of the dihydronicotinamide adenine dinucleotide (NADH) photosensitized by an anthrapyrazole-antitumor agent. The superoxide radical was detected as a DMPO adduct upon illumination of the system with visible light. Photoinduced generation of hydroxyl radicals is demonstrated by detection of DMPO adducts of OH scavengers, such as ethyl alcohol, sodium formate, and sodium azide. The dependence of the production of these spin adducts on the presence of catalase implies the involvement of hydrogen peroxide in that process. The production of hydrogen peroxide is demonstrated independently during oxygen consumption measurements with the Clark electrode technique.