Metal ion-flavonoid associations in bilayer phospholipid membranes.

The complexation process of the transition (Cu(2+), Fe(2+)) and heavy (Pb(2+)) metals with flavonoids (quercetin and rutin) was studied. The investigation was conducted using the spectrophotometric method in a medium containing phosphatidylcholine liposome membrane and in methanol. The Benesi-Hildebrand method was used to determine the constants of flavonoid-metal complex formation of the "charge transfer" type, and the Gibbs free energy change for that process. It was found that both quercetin and rutin are very effective at complexing transition atoms in both methanol and in the lipid bilayer. Pb(II) ions were only complexed in methanol. A short discussion is given on the importance of metal coordination processes in the context of lipid membrane peroxidation.