A thermodynamic and kinetic HO radical scavenging study and protein binding of baicalein

Abstract

Baicalein (BOH) is an essential flavone molecule with proven significant scavenging activity towards various reactive species, although the actual mechanism has not been fully elucidated. Three common mechanisms: Hydrogen Atom Abstraction (HAA), Radical Adduct Formation (RAF), and Electron Transfer (EA), for the reaction between BOH and HO• have been investigated thermodynamically and kinetically in water and penthylethanoate. Based on the pKa values of BOH, the percentages of various acid-base species were estimated and subsequently incorporated into the described procedures. Changes in Gibbs free energy of HAA reactions demonstrated the spontaneity of hydrogen transfer from each OH group of BOH with reaction rates of 1.8 × 107 and 7.5 × 104 M−1 s−1. This process occurred through Proton Coupled-Electron Transfer (PCET) mechanism. Reactions involving RAF processes were operable in six places, with rate constants ranging from 4.8 × 104 to 3.0 × 108 M−1 s−1. Reaction rates calculated for electron transfer from anionic species (BO-) were the kinetically most favorable reaction pathway of the order of 109 M−1 s−1, which unequivocally shows that these reactions are diffusion controlled. These results shed new light on BOH chemistry and its possible medical use. The molecular docking analysis was performed to identify the inhibition potency of the baicalein-anion against Glyoxalase I (GLOI) receptor. This study demonstrated that molecular docking analysis is an important tool for evaluating the interactions of biologically significant compounds, particularly their many acid-base forms.