BINARY MIXTURES OF QUERCETIN WITH SOME PHENOLIC ACIDS IN TERTBUTANOL- WATER SYSTEM: STUDY OF TERT-BUTOXYL RADICAL MEDIATED SYNERGISTIC INTERACTION THROUGH KINETIC APPROACH
G. Vijaya Lakshmi*
ABSTRACT
An upsurge in the number of studies on flavonoids has been stimulated by the potential health benefits arising from the antioxidant activities of these polyphenolic compounds. Functional hydroxyl groups in flavonoids mediate their antioxidant effects by scavenging free radicals and/or by chelating metal ions. The rates of oxidation of quercetin (QU) by t-BuOΣ radicals in the presence of phenolic acids viz., chlorogenic acid (CGA), caffeic acid (CA), rosmarinic acid (RA) and gallic acid (GA) have been studied by measuring the absorbance at suitable λmax spectrophotometrically. tert-butoxyl (t-BuOΣ) radicals were generated by the photolysis of tert-butyl hydroperoxide (t-BuOOH) in t-butanol-water (2:1 v/v) to scavenge ΣOH radicals. From competition kinetics, the rate constant of t- BuOΣ radical reaction with QU (kQu) has been determined to be 2.62 × 109 dm3mol-1 s-1. The quantum yields (fexpt) have been calculated from the experimentally determined rates of oxidation of QU/phenolic acids under different experimental conditions. The results indicated that QU showed synergistic/antagonistic interaction with polyphenols. CGA repaired QU to an extent of ~45% whereas QU was found to repair CA, RA and GA to an extent of ~96%, ~81% and ~42% respectively.
Keywords: quercetin, phenolic acids, t-BuO? radicals, synergistic interaction, repair reactions.
[Full Text Article]
[Download Certificate]