Kinetics of iron oxidation upon polyphenol binding

Abstract

Polyphenol prevention of iron-mediated DNA damage occurs primarily through iron binding. Once bound, iron in the Fe(2+)-polyphenol complex autooxidizes to Fe(3+) in the presence of O(2). To determine the correlation between the rate of Fe(2+)-polyphenol autooxidation and polyphenol antioxidant ability, kinetic studies at pH = 6.0 in the presence of oxygen were performed using UV-vis spectrophotometry. Initial rates of iron-polyphenol complex oxidation for epigallocatechin gallate (EGCG), methyl-3,4,5-trihydroxybenzoate (MEGA), gallic acid (GA), epicatechin (EC), and methyl-3,4-dihydroxybenzoate (MEPCA) were in the range of 0.14-6.7 min(-1). Polyphenols with gallol groups have faster rates of iron oxidation than their catechol analogs, suggesting that stronger iron binding results in faster iron oxidation. Concentrations of polyphenol, Fe(2+), and O(2) were varied to investigate the dependence of the Fe(2+)-polyphenol autooxidation on these reactants for MEGA and MEPCA. For these analogous gallate and catecholate complexes of Fe(2+), iron oxidation reactions were first order in Fe(2+), polyphenol, and O(2), but gallate complexes show saturation behavior at much lower Fe(2+) concentrations. Thus, gallol-containing polyphenols promote iron oxidation at a significantly faster rate than analogous catechol-containing compounds, and iron oxidation rate also correlates strongly with polyphenol inhibition of DNA damage for polyphenol compounds with a single iron-binding moiety.

Tea Polyphenols in Parkinson’s Disease

“…In a recent study examining the differential potency of a series of polyphenols to prevent DNA damage caused by Fe 2C and H 2 O 2 , it was found that among the 12 phenolic compounds tested, EGCG was the most potent, inhibiting over 90 % of the iron-mediated DNA break (Perron et al 2008). By correlating the pK a and IC 50 values of phenolic compounds for inhibition of Fe 2C /H 2 O 2 -induced neurotoxicity, it was suggested that the binding of the polyphenols to iron was essential for their anti-oxidant activity (Perron et al 2010). In one experiment performed on rat brain tissue, it was shown that lipid peroxidation was enhanced by iron ascorbate but inhibited in brain mitochondria by both black and green tea extracts (Jeong et al 2004).…”

A Review of the Antioxidant Mechanisms of Polyphenol Compounds Related to Iron Binding

“…This iron oxidation rate varies for polyphenol complexes, with gallate complexes having faster oxidation rates than catecholate complexes [148]. This oxidation of Fe 2?…”

Antioxidant and antimalarial properties of butein and homobutein based on their ability to chelate iron (II and III) cations: a DFT study in vacuo and in solution

“…charges and spin density on the Fe cation in the isolated and in the complexed state). A complete investigation on the iron···antioxidant complexes requires that both the kinetic and thermodynamic aspects be taken into consideration because studies have shown that Fe binding and the acceleration of Fe oxidation rate due to Fe binding strongly correlate with antioxidant activity [44,45]. The focus of this study is, however, based only on the thermodynamic properties of the complexes.…”