Faculty Collaboration Database

Mechanism of metal-independent decomposition of organic hydroperoxides and formation of alkoxyl radicals by halogenated quinones. Proc Natl Acad Sci U S A 2007 Mar 06;104(10):3698-702

Date

03/16/2007

Pubmed ID

17360415

Pubmed Central ID

PMC1820646

DOI

10.1073/pnas.0605527104

Scopus ID

2-s2.0-34247221459 (requires institutional sign-in at Scopus site)   84 Citations

Abstract

The metal-independent decomposition of organic hydroperoxides and the formation of organic alkoxyl radicals in the absence or presence of halogenated quinones were studied with electron spin resonance (ESR) and the spin-trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO). We found that 2,5-dichloro-1,4-benzoquinone (DCBQ) markedly enhanced the decomposition of tert-butylhydroperoxide (t-BuOOH), leading to the formation of the DMPO adducts with t-butoxyl radicals (t-BuO* and methyl radicals *CH(3)). The formation of DMPO/t-BuO* and DMPO/*CH(3) was dose-dependent with respect to both DCBQ and t-BuOOH and was not affected by iron- or copper-specific metal chelators. Comparison of the data obtained with DCBQ and t-BuOOH with those obtained in a parallel study with ferrous iron and t-BuOOH strongly suggested that t-BuO* was produced by DCBQ and t-BuOOH through a metal-independent mechanism. Other halogenated quinones were also found to enhance the decomposition of t-BuOOH and other organic hydroperoxides such as cumene hydroperoxide, leading to the formation of the respective organic alkoxyl radicals in a metal-independent manner. Based on these data, we propose a mechanism for DCBQ-mediated t-BuOOH decomposition and formation of t-BuO*: a nucleophilic attack of t-BuOOH on DCBQ, forming a chloro-t-butylperoxyl-1,4-benzoquinone intermediate, which decomposes homolytically to produce t-BuO*. This represents a mechanism of organic alkoxyl radical formation not requiring the involvement of redox-active transition metal ions.

Author List

Zhu BZ, Zhao HT, Kalyanaraman B, Liu J, Shan GQ, Du YG, Frei B

Author

Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Benzene Derivatives
Benzoquinones
Chelating Agents
Cyclic N-Oxides
Electron Spin Resonance Spectroscopy
Free Radicals
Ions
Metals
Models, Chemical
Models, Molecular
Oxidation-Reduction
Quinones
Spectrometry, Mass, Electrospray Ionization
Spin Labels