Mechanism for diffusion-controlled scavenging of bound-ROS by propofol and ferulic acid

Reactive oxygen species are known to have a harmful activity in living systems. It attracts the attention of researchers due to their capability of damaging crucial biomolecules such as nucleic acids, lipids, proteins, polyunsaturated fatty acids, and carbohydrates and which results many human ailments: atherosclerosis, cancer, diabetes, inflammation, cardiovascular diseases, and neurological disorders. Hence, the investigation of the already known compounds exhibiting antioxidant properties is still an important scientific challenge. So reaction with Co(II)-bound superoxo complex, [(NH₃)₅Co(O₂)Co(NH₃)₅]⁵⁺ (MBSC) and Popofol (PPF), Ferulic Acid (FA) is chosen to study the antioxidant activity of PPF and FA. Redox properties of Popofol (PPF) and Ferulic Acid (FA) which are two phenolic antioxidants are studied through the reduction of Co(II)-bound superoxo complex, [(NH₃)₅Co(O₂)Co(NH₃)₅]⁵⁺ (MBSC) in aqueous acidic media ([H⁺] = 0.02–0.70 M) under pseudo-first-order condition. For both the PPF and FA, the observed rate increase with the increase in [PPF] and [FA] and the decrease with media [H⁺] and ionic strength, I. The kinetic analysis reveals that the deprotonated conjugate bases from PPF and FA reduces MBSC with the diffusion-controlled rate of ~ 10⁸ and ~ 10¹¹ M⁻¹ s⁻¹. Since, the decrease in k_o values with increase in V/V D₂O were not significant, we can propose for a simple electron-transfer (ET) mechanism, rather than proton-coupled electron transfer (PCET) or hydrogen-atom transfer (HAT) mechanism for the reduction in bound superoxide by PPF and FA. The antioxidant property of propofol and ferulic acid has been evaluated by various methods but in our study, the novelty lies on the exploration of the real insight of their antioxidant property by studying the chemical mechanism of their redox properties with MBSC.