Tautomerism and Radical-Scavenging Activity of Edaravone by DFT Methods

A detailed theoretical study of the edaravone was carried out using DFT method using B3LYP/6-31G* basis set, with the objective to clarify the scavenging mechanism and influence of edaravone tautomerism under acid condition, which will be helpful to elucidate the radical-scavenging mechanisms in the ischemic process. Previous theoretical studies, tautomerization, solvent effects, and electron abstraction no were considered. The stability and reactivity were determined through geometric and energetic parameters were realized in gas phase and PCM methods in water and methanol. The acid or basic conditions were considered by bond dissociation or protonation energies may undergo anion or cation products, respectively. The antioxidant properties were calculated through HOMO, ionization potential (IP), and bond dissociation energies (BDE). HOMO and IP values showed that N–H tautomer is better antioxidant while BDE values showed that O–H tautomer is better antioxidant. The protonation is thermodynamically more favored than deprotonation. Furthermore, the protonation energy explain, theoretical, the reduced difference between N and O protonation. N–H tautomer is better antioxidant by electron abstraction while O–H tautomer is better antioxidant by hydrogen abstraction. The protonation is thermodynamically more favored than deprotonation. The solvent effect decreased energies barriers to isomerization in O–H or N–H tautomers.