title: An electron spin resonance study of the reduction of peroxides by anthracycline semiquinones.
abstract: Direct and spin-trapping electron spin resonance methods have been used to study the reactivity of semiquinone radicals from the anthracycline antibiotics daunorubicin and adriamycin towards peroxides (hydrogen peroxide, t-butyl hydroperoxide and cumene hydroperoxide). Semiquinone radicals were generated by one-electron reduction of anthracyclines, using xanthine/xanthine oxidase. It is shown that the semiquinones are effective reducing agents for all the peroxides. From spin-trapping experiments it is inferred that the radical product is either OH (from H2O2) or an alkoxyl radical (from the hydroperoxides) which undergoes beta-scission to give the methyl radical. The rate constant for reaction of semiquinone with H2O2 is estimated to be approx. 10(4)-10(5) M-1 X s-1. The reduction does not appear to require catalysis by metal ions.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D003630:Daunorubicin / Q000031:analogs & derivatives* / Q000378:metabolism; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000378:metabolism*
chemical_list: C024703:adriamycin semiquinone radicals; C041790:daunorubicin semiquinone radicals; D004317:Doxorubicin; D006861:Hydrogen Peroxide; D003630:Daunorubicin