Electrochemical and theoretical complexation studies for Zn and Cu with individual polyphenols

Abstract

Zn and Cu interactions with three selected flavonoids (catechin, quercetin and rutin) have been electrochemically monitored. It has been shown that catechin takes 1 atom of metal per molecule; quercetin takes 2 atoms, and rutin is able to take up to 3 atoms. Not all ligands bind metals equally strong, and weakly bonded metals can be distinguished. Zn shows a sluggish kinetics and, at the same time, the highest conditional formation constants. The method could be applied to a real sample. Theoretical models are proposed for the most favourable compounds.

Complexing capacity profiles of naturally occurring ligands in Tempranillo wines for Cu and Zn

“…Zn and Cu have both been chromatographically found to specifically associate to cyanydin-3-glucoside which is one of the most abundant anthocyanins in red wines [13] and their complexing capability with individual polyphenols in different media has been electrochemically evaluated [14][15][16][17]. Presence of metals accompanying natural ligands in commercial wines comes as a result of their mutual interaction along winemaking where metals intervene in multiple processes such as complex formation [18], polymerization, flocculation and precipitation [6,10,19].…”

Epigallocatechin-3-gallate affects the growth of LNCaP cells via membrane fluidity and distribution of cellular zinc

“…Thermo-gravimetric and atomic absorption spectrophotometric studies indicate that the 3-OH-4-oxo and 3-OH-4-OH moieties are the most likely binding sites of flavonoids for metals. Accordingly, catechin could form 1:1 complex with either Zn 2+ or Cu 2+ , which can be monitored through the linearization algorithms as competitive with pre-concentration of the metal ions on the mercury electrode (Esparza et al, 2005). Kagaya et al(2002) reported that it was the formation of zinc-EGCG complex that enhanced effect of zinc on hepatoprotectivity of EGCG in isolated rat hepatocytes.…”

Chromatic characterisation of three consecutive vintages of Vitis vinifera red wine

“…Several authors have referred to this question and have pointed out the disruption of the equilibria that might take place in diluted samples. In our previous works [7,24,28], we have always tried to preserve the naturally occurring equilibria by using pH 4 buffered conditions. In this occasion we have studied the effect of dilution on colour analysis by subjecting all samples to a 1:5 dilution with an 8% ethanol containing buffer solution.…”