Quantitative treatment of the kinetics of free-radical-mediated damage. Protection by free-radical scavengers

Pino E.; Lissi, EA

Abstract

Equations are derived to quantitatively describe the effect of a free-radical scavenger upon the rate of a radical-mediated process that senses the steady-state free-radical concentration. The dependence of the ratio R°IR (where R° is the rate of the process in the absence of additive) upon the additive concentration depends upon the type of reaction that determines the free-radical lifetime. Normal Stern-Volmer-like behavior is expected only when the lifetime of the radical in the absence of free-radical scavengers is determined by the concentration of the substance employed as the reporter of the free-radical concentration. These predictions are tested in a system comprised of 2,2?-azobis[2-methylpropanimidamide dihydrochloride) as the free-radical source, c-phycocyanin as the reporter molecule, and Trolox (= 3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid) tryptophan and 4-methoxyphenol as peroxyl-radical scavengers. The data obtained with Trolox show that it behaves as a nearly ideal free-radical scavenger. On the other hand, the data obtained with tryptophan and 4-methoxyphenol as scavengers show, when plotted according to the Stern-Volmer equation, a strong downward curvature. These results are explained in terms of c-phycocyanin bleaching by scavenger-derived free radicals.

Más información

Título según WOS: Quantitative treatment of the kinetics of free-radical-mediated damage. Protection by free-radical scavengers
Título según SCOPUS: Quantitative treatment of the kinetics of free-radical-mediated damage. Protection by free-radical scavengers
Título de la Revista: HELVETICA CHIMICA ACTA
Volumen: 84
Número: 12
Editorial: WILEY-V C H VERLAG GMBH
Fecha de publicación: 2001
Página de inicio: 3677
Página final: 3685
Idioma: English
URL: http://doi.wiley.com/10.1002/1522-2675%2820011219%2984%3A12%3C3677%3A%3AAID-HLCA3677%3E3.0.CO%3B2-X
DOI:

10.1002/1522-2675(20011219)84:12<3677::AID-HLCA3677>3.0.CO;2-X

Notas: ISI, SCOPUS