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Abstract

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.

Reduction of Fe(III) Ions Complexed to Physiological Ligands by Lipoyl Dehydrogenase and Other Flavoenzymes in Vitro

“…ent on the characteristics of the chelating ligand (12,25,40 (25,40,55,57,73,74). Therefore, kinetic properties of the lipoyl dehydrogenase-mediated Fe(III) reduction and NAD(P)H oxidation can be assessed only in the absence of oxygen (see below).…”

“…55 ever, the ability of this enzyme to reduce Fe(III) ions complexed to physiological ligands has not been studied, which is more surprising as lipoyl dehydrogenase has been reported to reduce the biochemical standard one-electron oxidant [Fe(CN) 6 ] 3Ϫ very rapidly (26).…”

Interactions between flavonoids and hemoglobin in lecithin liposomes

“…They respond to light and are known to control the level of auxins, the regulators of plant growth and differentiation. Consumption of plants and plant products that are rich in flavonoids, such as cocoa, wine, tea, and berries, has been related with protective effects against cardiovascular disease and certain forms of cancer [4,5]. They have been found to act as free-radical scavengers and have been widely studied for their antioxidant activity in vitro.…”

Synthesis, Characterization and the Antioxidative Activity of Copper(II), Zinc(II) and Nickel(II) Complexes with Naringenin

“…The natural compounds are potential antibacterial, anticancer, antioxidant, antiinflammatory, and antiallergic agents since they stimulate or inhibit a wide variety of enzyme systems as pharmacological agents [6]. The best-known flavonoids, such as quercetin, morin and rutin, have been thoroughly studied in references [7][8], but naringenin is one of the lesser-known flavonoids except for being used as antioxidant, antibacterial and anticancer studied as agents [9].…”