Radical scavenging activity of bromophenol analogs: analysis of kinetics and mechanisms.

Context: This theoretical study explores the antioxidant activity of five bromophenol analogs, with a particular focus on their interaction with different solvent environments of varying polarities. Key findings include the correlation between increased solvent polarity and enhanced antioxidant activity of these analogs, comparable in some instances to ascorbic acid. Notably, compound 5, developed by our research team, demonstrates superior antioxidant activity in both lipid and aqueous solutions, surpassing that of ascorbic acid and other tested analogs. This research contributes to the understanding of bromophenol analogs, presenting the first known kinetic and chemical stability data such as rate constants, pKa values, and branching ratios for reactions with the methylperoxyl radical (CH3OO•).

Methods: The computational analyses were conducted using the Gaussian 09 software suite at the M05-2X/6-31 + G(d) computational level. These analyses employed conventional transition state theory to account for various potential mechanisms and effects of solvent polarity on the antioxidant activities of bromophenol analogs. The study meticulously calculated enthalpy under standard conditions (298.15 K and 1 atm) with necessary thermodynamic corrections. Additionally, the Quantum Mechanics-based Test for Overall Radical Scavenging Activity (QMORSA) protocol guided the evaluation of radical scavenging activity, ensuring a comprehensive assessment of the antioxidant potential of the compounds.