Effect of psoralens on Fenton‐like reaction generating reactive oxygen species

Psoralens (psoralen, 5‐methoxypsoralen, 8‐methoxypsoralen, khellin, and visnagin) in 1 m M doses were shown to enhance the generation of reactive oxygen species, such as the hydroxyl radical (HO · ), the superoxide anion radical (), and singlet oxygen ( 1 O 2 ), from the system generating chemiluminescence (CL), as well as free radicals in the absence of light. The system that generated CL was made up of CoCl 2 and H 2 O 2 . Incubation of psoralens in 0.2 m M doses with the generating system showed that only 8‐methoxypsoralen and khellin have antioxidative effects. Antioxidative effects were also observed in the case of visnagin but in low concentration (0.05 m M ). High doses of psoralens (1 m M ) showed prooxidative effects. Measurements were done using a deoxyribose assay, the CL method, and spin‐trapping with 5,5‐dimethyl‐1‐pyrroline‐ N ‐oxide and 2,2,6,6‐tetramethylpiperidine combined with electron spin resonance spectroscopy and spectrophotometry methods. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 59–68, 2003