A theoretical study on the antioxidant properties of methoxy-substituted chalcone derivatives: A case study of kanakugiol and pedicellin through their Fe (II and III) coordination ability

摘要

A theoretical study on the antioxidant properties of two chalcone derivatives, kanakugiol and pedicellin, is performed by considering their Fe2+ and Fe3+ coordination ability. The objective of the study is to elucidate the factors influencing the stability of the isolated conformers, the nature of the complexes, metal... ligand stability, metal ion affinities (MIA) and electronic properties of the cations before and after coordination to the ligand. The study is performed using the B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d,p) method. The LANL2DZ pseudo-potential is selected to describe the Fen+ ions. Time-dependent density functional theory (TDDFT) method is used to assess the electronic UV-Vis spectra of the isolated chalcones and their complexes with Fen+ ions. The results suggest that the preferred complexes are those in which the Fe ion is coordinated at the hydroxyl-methoxy and hydroxyl-keto sites for kanakugiol and methoxy-keto site for pedicellin. Both kanakugiol and pedicellin have potential to chelate iron ions as demonstrated by their high MIA values in vacuo and in water solution. However, the ability of pedicellin to chelate iron is slightly lower than that of kanakugiol, indicating that the presence of the hydroxyl group has an effect of enhancing the metal binding abilities of the chalcone derivatives. In all the complexes obtained in vacuo, kanakugiol and pedicellin exhibit the ability to reduce the Fen+ ion. In water solution (which mimics the environment in biological systems or studies performed in vivo), Fe3+ is reduced to Fe2+ upon coordination to the ligand while the oxidation number of Fe2+ upon coordination to the ligand remains virtually unchanged.