EVALUATION OF THE EXTINCTION COEFFICIENT OF THE ABTS DERIVED RADICAL CATION

The exact knowledge of the value of the extinction coefficient of the ABTS derived radical is necessary for its quantitative use in the evaluation of the antioxidant capacity of pure compounds and/or complex mixtures. We have performed experiments in order to stablish its lower and upper limits of its value. The limits obtained, 1.0 x 10(4) M-1 cm-1 <= epsilon 734 <= 1.6 x 10(4) M-1 cm-1 are fully compatible with previously reported data. However, the use of these values leads to large stoichiometric coefficients for the reaction of these radicals with simple substrates, such as monophenols or tryptophan. Conocer el valor exacto del coeficiente de extinción del radical catión derivado del ABTS es un pre-requisito para su empleo en la evaluación de la capacidad antioxidante de compuestos puros polifuncionales o mezclas complejas. Nosotros hemos realizado emperimentos que permiten establecer límites inferiores y superiores para su valor. Los límites obtenidos 1.0 x 10(4) M-1 cm-1 <= épsilon 734 <= 1.6 x 10(4) M-1 cm-1 son compatibles con los valores reportados en la literatura. Sin embargo, el uso de estos valores conduced a coeficientes estequiométricos anormalmente altos para sus reacciones con comuestos simples como monofenoles y triptofano.