Photosensitized production of superoxide anion by monochromatic (290-405 nm) ultraviolet irradiation of NADH and NADPH coenzymes.

Abstract

Abstract— The reduced pyridine coenzymes NADPH and NADH produced superoxide anion(“CK”) from ground state molecular oxygen when irradiated by ultraviolet (UV) radiation extending from 290 to 405 nm as detected by cytochrome c reduction. Superoxide dismutase (SOD), but not catalase or heat‐inactivated SOD, decreased the amount of cytochrome c reduced, indicating that O2− was responsible for the reduction of cytochrome c. Decreased oxygen tension during irradiation also inhibited production of O2−. Quantum yields for the production of the anion were in the region of 10−7 to 10−9 mol per photon. These data indicate that NADH and NADPH can act as type II photosensitizers of both far‐and near‐UV radiation, and that the deleterious biological effects of exposure to these radiations such as erythema and dermal carcinogenesis may be mediated at least in part through the generation of O2−.