Hydroxyl radical formation by dithranol

Abstract Ethene formation from 2-keto-thiomethyl-butyric acid (KMBA) was used to measure hydroxyl radical generation from the antipsoriatic drug dithranol in phosphate buffer pH 7.8. Because the singlet oxygen ( 1 O 2 ) sensitizer, rose bengale, showed enlarged production of ethene when irradiated in the presence of KMBA, experiments were performed in the dark in order to avoid 1 O 2 production by dithranol. KMBA was converted to ethene by dithranol under aerobic conditions, whereas ethene formation was negligible in the absence of oxygen. Addition of catalytic amounts of FeCl 3 resulted in increased ethene formation, indicating the catalysis of a superoxide-driven Fenton-reaction. O − 2 - and OH-scavengers such as rutin, catechin, dimethyl sulfoxide, mannitol, ethanol, sodium salicylate and propyl gallate as well as catalase and superoxide dismutase inhibited ethene formation.