Research on the chelation between quercetin and Cr(III) ion by Density Functional Theory (DFT) method

In order to locate the exact chelation site, the chelation between quercetin and Cr(III) ion is studied using the theoretical methods. Many different potential complexes, formed with natural and deprotonated quercetin chelating bare and hydrated Cr(III) ion, respectively, are studied by using Density Functional Theory method. Both total and binding energies are calculated. The results from the studies indicate that Cr(III) ion is affine in forming a complex with quercetin at the 5-hydroxy-4-keto site and that deprotonated quercetin has stronger chelating power than natural quercetin. Apart from the theoretical studies, the experiments are performed to modify the theoretical conclusions. Meanwhile, quercetin-Cr(III) complex has been synthesized, and the chelation site is analyzed using IR spectroscopy and UV/vis spectrum. The experimental results are found to have the same conclusions as those by theoretical studies. (C) 2008 Elsevier B.V. All rights reserved.