Evaluation of Free Radical Quenching Ability of Quinoline Acids through in vitro and Theoretical Studies

Abstract

Drugs based antioxidants are commonly suggested as targets while designing new medicines. All sorts of pharmaceutical drug development benefit from the extremely desirable quinoline moiety with antioxidant. In this work, the scavenging behaviour of four quinoline derivatives (Q1-Q4) towards DPPH, H2O2, ABTS and superoxide activity were investigated. According to the in vitro inhibition concentration (IC50), quinoline derivative Q1 showed high antioxidant potential. Additionally, the theoretical DFT gas phase calculations of HOMO-LUMO, MEP, NPA and NBO are used to study the conjugating systems in radicals and showed that the N-H site acts more favourable than the O-H site for the radical attack. The calculated bond dissociation energy (BDE) values demonstrated that compound Q1 follows the HAT mechanism and while the calculated ionization potential (IP) and proton dissociation energy (PDE) values showed that Q4 follows the SET-PT route. The results of these two mechanisms demonstrated that radical quenching activity occurs at the N-H and O-H sites. The spin density demonstrates that both radicals are delocalized uniformly across the molecule.