Degradation mediated OH radical generation from synthetic cyclic peroxides: ESR studies

Reaction of synthetic cyclic peroxide, 4-ethoxy-1,4-dihydro-2,3-benzodioxin-1-ol, with ferricytochrome c in vitro

When synthetic cyclic peroxide, 4-ethoxy-1,4-dihydro-2,3-benzodioxin-1-ol (Bd), was added to a ferricytochrome c solution, the Soret band of cytochrome c at 410 nm gradually disappeared due to heme degradation. The reaction was prominent at pH less than 7.5. At alkaline pH the reaction was markedly suppressed, despite the fact that decomposition of Bd itself occurred more rapidly at alkaline than acidic pH. Ferricytochrome c heme degradation occurred under anaerobic as well as aerobic conditions. On the other hand, ferrocytochrome c reacted directly with Bd and was oxidized, probably through the electron transfer mechanism. These results, together with the effect of deuterium isotope on the reaction, indicate that the heme degradation is mediated by the short-lived oxidative species generated directly from Bd decomposition. At alkaline pH, heme reduction rather than degradation predominated. The reaction was quantitatively inhibited by superoxide dismutase. Thus it was expected that the reduction was mediated by O2- produced secondarily from O2 in the medium. The Bd-mediated cytochrome c degradation was weakly inhibited by dimethyl sulfoxide but was inhibited upto approximately 80% by mannitol or thiourea. Non-specific radical scavengers such as ascorbate inhibited the reaction almost completely.

Spin trapping: ESR parameters of spin adducts

Spin trapping has become a valuable tool for the study of free radicals in biology and medicine. The electron spin resonance hyperfine splitting constants of spin adducts of interest in this area are tabulated. The entries also contain a brief comment on the source of the radical trapped.

Mechanism of antibacterial action: electron transfer and oxy radicals

Most of the main categories of bactericidal agents, namely, aliphatic and heterocyclic nitro compounds, metal derivatives and chelators, quinones, azo dyes, and iminium-type ions, are proposed to exert their action by a unified mechanism. The toxic effect is believed to result generally from the catalytic production of reactive oxygen radicals that usually arise via electron transfer. Cyclic voltammetry was performed on a number of these agents. Reductions were for the most part reversible, with potentials in the favorable range of -0.20 to -0.58 V.