title: Diaziquone as a potential agent for photoirradiation therapy: formation of the semiquinone and hydroxyl radicals by visible light.
abstract: When diaziquone was irradiated with 500 nm visible light, hydroxyl free radicals as well as the diaziquone semiquinone were produced. The diaziquone semiquinone is a stable free radical that exhibits a characteristic 5-line electron spin resonance (ESR) spectrum. Since hydroxyl free radicals are short lived, and not observable by conventional ESR, the nitrone spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) was used to convert hydroxyl radicals into longer lived ESR detectable spin adducts. The formation of hydroxyl radicals was further confirmed by investigating reactions in which hydroxyl radical scavangers, sodium formate and dimethylsulfoxide, compete with the spin traps DMPO or POBN (alpha-(4-Pyridyl-1-oxide)-N- tert-butylnitrone) for hydroxyl free radicals. The products of these scavenging reactions were also trapped with DMPO or POBN. If drug free radicals and hydroxyl free radicals are important in the activity of quinone-containing antitumor agents, AZQ may have a potential in photoirradiation therapy or photodynamic therapy.
mesh_terms: D001388:Aziridines / Q000627:therapeutic use*; D001389:Azirines / Q000627:therapeutic use*; D016227:Benzoquinones; D003497:Cyclic N-Oxides; D004121:Dimethyl Sulfoxide; D004578:Electron Spin Resonance Spectroscopy; D006878:Hydroxides; D017665:Hydroxyl Radical; D008027:Light; D009589:Nitrogen Oxides; D010789:Phototherapy; D011725:Pyridines; D011809:Quinones
chemical_list: D001388:Aziridines; D001389:Azirines; D016227:Benzoquinones; D003497:Cyclic N-Oxides; D006878:Hydroxides; D009589:Nitrogen Oxides; D011725:Pyridines; D011809:Quinones; C043438:alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone; C025232:semiquinone radicals; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; C029108:diaziquone; D004121:Dimethyl Sulfoxide