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

Abstract

A theoretical study on the antioxidant and antimalarial properties of butein and homobutein has been performed by considering their Fe2+ and Fe3+ chelation ability. In order to elucidate the origin of the antioxidant and antimalarial properties of these compounds, the study attempts to investigate the nature of the complex structures, ligand···Fen+ stabilities and electronic properties of the Fe cations before and after complexation. The investigation considered the neutral and the deprotonated species of butein and homobutein interacting with the Fe cations as well as the deprotonated species of butein and homobutein interacting with micro-solvated Fe2+ or Fe3+ cation. The study has been performed using B3LYP/6-31+G(d,p) method. The LANL2DZ pseudo-potential was selected to describe the Fe cations. Final energies were obtained using the B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d,p) method. The binding energies depend on the media (it is higher in vacuo than in water solution), the nature of the cation (it is higher for Fe3+ than for Fe2+), the nature of the ligand and the Fen+ coordination site on the ligand (it is highest for the bidentate Fe coordination to O2′ and O9 atoms and lowest for the Fe coordination on the π system of the aromatic ring). The charge on Fen+ decreases on coordination to the ligand. AIM analysis suggests that the strong cation···ligand interactions are more likely covalent than ionic in vacuo and entirely ionic in solution. The ability of the ligands to reduce the Fe cation coupled with the strong iron-binding properties has significant implication on their antioxidant and antimalarial activities.