On the ability of four flavonoids, baicilein, luteolin, naringenin, and quercetin, to suppress the Fenton reaction of the iron-ATP complex

Four flavonoids, baicilein, luteolin, naringenin, and quercetin were investigated for their ability to suppress the Fenton reaction characteristic of the iron-ATP complex. Absorption spectroscopy indicates that under the conditions of 18.75% aqueous methanol, 0.0625 mM HEPES pH 7.4 buffer and 1.5:1 quercetin/iron-ATP ratio a mix ligand complex formed. All four flavonoids were found to interfere with the voltammetric catalytic wave associated with the iron-ATP complex in the presence of H2O2. Quercetin and luteolin were able to completely suppress the catalytic wave of the iron-ATP/H2O2 system when a minimum ratio of 1.5:1 of the flavonoid to iron-ATP was reached. At this ratio, the ability of the studied series of flavonoids to suppress the Fenton reaction characteristic of iron-ATP follows as quercetin approximate to luteolin > naringenin approximate to baicilein. Both quercetin and luteolin contain catechol on the B ring, which may enhance the iron chelation of these species over baicilein and naringenin. The common structural feature of all of these flavonoids is the 4-keto, 5-hydroxy region, which may also contribute to the chelation of iron.