Lipid Peroxidation-Dependent Chemiluminescence from the Cyclization of Alkylperoxyl Radicals to Dioxetane Radical Intermediates

• Published in: Chemical research in toxicology 1997-10, Vol.10 (10), p.1090-1096
• Main Authors: Timmins, Graham S., dos Santos, Rosemeire E., Whitwood, Adrian C., Catalani, Luiz H., Di Mascio, Paolo, Gilbert, Bruce C., Bechara, Etelvino J. H.
• Format: Article
• Language: English
• Subjects: Electron Spin Resonance Spectroscopy; Free Radicals; Horseradish Peroxidase; Lipid Peroxidation; Luminescent Measurements
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx970075p

This work reveals a novel mechanism for triplet carbonyl formation (and hence chemiluminescence) during lipid peroxidation, whose chemiluminescence has been attributed to both triplet carbonyls and singlet oxygen. As a model for polyunsaturated fatty acid hydroperoxides, we have synthesized 3-hydroperoxy-2,3-dimethyl-1-butene by photooxygenation of tetramethylethylene. One-electron oxidation of this hydroperoxide with heme proteins and peroxynitrite to the corresponding alkylperoxyl radical results in chemiluminescence, both direct and 9,10-dibromoanthracene-2-sulfonate-sensitized, the latter attributed to the formation of triplet acetone. It is postulated that triplet acetone results from the cyclization of the alkylperoxyl radical to a dioxetane radical intermediate followed by its thermolysis. This is supported by EPR spin-trapping experiments in which discrimination between carbon-centered radicals derived from the alkyloxyl and alkylperoxyl radicals is achieved through the use of one-electron oxidants and reductants, e.g., FeII and TiIII.