Theoretical insights into the direct radical scavenging activities of 8-hydroxyquinoline: Mechanistic, thermodynamic and kinetic studies

• Published in: Computational and theoretical chemistry Vol. 1198; p. 113174
• Main Authors: Kennet Nkungli, Nyiang, Numbonui Tasheh, Stanley, Didier Tamafo Fouegue, Aymard, Kogge Bine, Fritzgerald, Numbonui Ghogomu, Julius
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2021
• Subjects: 8-Hydroxyquinoline; DFT; NEB-TS; Radical-scavenging; RAF mechanism; 8-Hydroxyquinoline; Radical-scavenging; DFT; NEB-TS; RAF mechanism
• ISSN: 2210-271X
• DOI: 10.1016/j.comptc.2021.113174

•From our thermochemical and kinetics data, 8HQ is a potent •OH radical scavenger.•8HQ is found to be an efficient RAF-dependent direct •OH radical scavenger.•Fukui function and reaction free energy agree excellently in RAF site identification.•Non-bridgehead carbons ortho/para to 8HQ’s hydroxyl group are the best RAF sites.•The DFT and NEB-TS methods are used herein to locate minimum energy reaction paths. A Density Functional Theory study of the mechanisms, thermodynamics and kinetics of some antiradical reactions of 8-hydroxyquinoline (8HQ) against •OH is reported. The radical adduct formation (RAF), hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms are investigated. The results indicate that 8HQ is an efficient RAF-dependent direct •OH radical deactivator, in accordance with recent experimental findings that 8HQ is a potent scavenger of reactive oxygen species (ROS). The ortho and para carbons to the hydroxyl group in 8HQ, not including the bridgehead carbon, are identified as highly favorable RAF sites in polar and nonpolar solvents. Interestingly, RAF via the para carbon is thermodynamically feasible, fast (with apparent rate constants 2.867 × 108 and 1.012 × 107M-1s-1 in water and benzene, respectively), and contributes over 70% of 8HQ’s antioxidant capacity. Our results support the viewpoint that direct ROS scavenging plays a key role in 8HQ’s anti-neurodegenerative activities.