Kinetic studies of the oxidation of quercetin, rutin and taxifolin in the basic medium by (ethylenediaminetetraacetato) cobalt(III) complex

The quercetin in 0.01 M NaOH solution underwent steady oxidation when it was exposed to air with the formation of the quinone product. For the taxifolin and rutin, the oxidation occurred only when the solutions were saturated with O2, but very slowly. The kinetics of the oxidation of flavonoids in 0.01 M NaOH solution by Co(edta)− complex was carried out and the rate constants are 3.44 × 102, 1.04 × 10− 1 and 1.46 × 10− 2 M− 1 s− 1 for quercetin, rutin and taxifolin, respectively, at μ = 0.10 M LiClO4. The deprotonation of the C3 hydroxyl group and the conjugation between pyrone and catechol rings account for the reactivity of quercetin.