Experimental and theoretical study on DPPH radical scavenging mechanism of some chalcone quinoline derivatives

In this study, the antioxidant capacity of three chalcone derivatives was evaluated by DPPH free radical scavenging. Experimental data showed low antioxidant activity (IC50 +/- SD) of these molecules in comparison with BHT. The mechanism of DPPH radical scavenging elucidated by means of density functional theory (DFT) calculations. The tested compounds and their corresponding radicals and anions were optimized using B3LYP functional with 6-31G (d,p) basis set in the gas phase. The C-PCM model was used to perform solvent medium calculations. On the basis of theoretical calculations, it was shown that HAT mechanism was predominant in the gas phase, whereas SET-PT and SPLET mechanisms were favored in the presence of the solvent. Moreover, the HOMO orbitals and spin density distribution was evaluated to predict the probable sites for free radical attack. (C) 2017 Elsevier B.V. All rights reserved.