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Journal of the Chilean Chemical Society

On-line version ISSN 0717-9707

Abstract

HENRIQUEZ, CAROLA; ALIAGA, CAROLINA  and  LISSI, EDUARDO. KINETICS PROFILES IN THE REACTION OF ABTS DERIVED RADICALS WITH SIMPLE PHENOLS AND POLYPHENOLS. J. Chil. Chem. Soc. [online]. 2004, vol.49, n.1, pp.65-67. ISSN 0717-9707.  http://dx.doi.org/10.4067/S0717-97072004000100011.

The kinetic profile associated to the reaction of phenols with 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) derived radicals is extremely dependent of the characteristics of the substrate. In particular, polyphenols present complex profiles that can be associated to successive reactions of different reactive centers present in the target molecule. Also, changes in the secondary reactions of the produced radicals can lead to a partial recovery of the ABTS radical concentration at intermediate reaction times, as observed employing 1,4-dihydroxybenzene. Although the kinetic profiles of monophenols are considerably simpler, the stoichiometry of the process is unexpected. For example, the data obtained imply that four radicals are consumed by each p-tertbutylphenol molecule introduced into the system. This large stoichiometric coefficient is not compatible with a simple, phenol promoted, back reduction of the ABTS radical. These results, as well as the overshoot observed employing 1,4-dihydroxybencene, cast doubts on the use of ABTS based methodologies to quantitatively measure the capacity of a given compound to trap free radicals or the amount of free radical scavengers present in complex mixtures

Keywords : ABTS; phenols; antioxidant capacities; free radical scavenging.

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