Antioxidant activity of some khellin derivatives: a density functional theory study

Abstract

Background The antioxidant activity of some benzofuran and 2H-pyran-2-one derivatives of naturally occurring khellin and visnagin was theoretically investigated using a quantum chemical method, density functional theory. These molecules possess a variety of biological and pharmacological activities including antioxidant activity. Materials and methods The calculations were carried out using Gaussian 03 computational package in gas phase with the purpose of obtaining the intrinsic properties of the molecules studied, free of any interaction. The geometries of neutral species and their respective radicals and radical cations were optimized using PM3 and density functional theory/B3LYP calculations with cc-pVDZ basis set. Results As they possess O-H, N-H, or both O-H and N-H bonds, we chose to investigate theoretically their antioxidant activity via H-atom transfer or single electron transfer pathway. In the gas phase, the ionization potential, the highest occupied molecular orbital (HOMO), bond dissociation energies of hydroxyl group O-H and N-H [bond-dissociation enthalpy (BDE)O-H–BDEN-H], and spin density distribution are carried out. Molecule 14 showed potential antioxidant activity as BDE for the N-H bond was found to be 84.71 and for the O-H bond was 85.32, whereas the ionization potential was 6.26 and the EHOMO was 5.39. Conclusion Based on the antioxidant activities of 15 derivatives of naturally occurring khellin and visnagin, they were found to be potent antioxidant compounds comparable to quercetin or vitamin C.