Abstract

Sahil A. Alasady, Yasmeen H. Muhamad, Rana S. Ahmed.

Mercury, one of the toxic metals, that is highly toxic to humans, it released into the environment as a result of both natural processes as well as due to anthropogenic activities. Chelation therapy is a medical procedure that involves the administration of chelating agents to remove heavy metals from the body. The application of natural chemical chelators is one of the traditional methods of removing toxic metals from the body. Flavonoids are natural products widely distributed in plant and form one of the main classes of secondary metabolites. They can coordinate metal ions and form complexes due to the presence of carbonyl and hydroxyl groups. The review considers the possible role of flavonoids as natural chelating and detoxifying agents. Natural flavonoids such as Quercetin and Catechin used as models to elucidate their impact on against metal toxicity. The equilibrium constants and the thermodynamic parameters for complex formation between natural flavonoids and Hg (II) Ion have been determined by Spectrophotometric measurements in water and ethanol at different temperatures. The stoichiometry of the complexes was determined using Job's method. Both Quercetin-Hg(II) and catechin-Hg (II) complexes presented 1:1 stoichiometry. Thermodynamic parameters (∆G, ∆H and ∆S) of the complexes were obtained from the various Van’t Hoff’s plots of lnK against 1/T. An attempt was made to obtain more information from the quantum chemical calculations about the structures of both free and complex forms of flavonoid. Quantum chemical calculations were performed to ascertain the correlation between their experimental results. The density function theory (DFT) calculation at the B3LYP method with LanL2DZ basis set are used to investigate the optimized geometry parameters of flavonoids and their complexes with Hg (II) metal. Moreover, HOMOâ€�LUMO energies of the mentioned compounds have been computed.