A combined experimental and theoretical approach for radical-scavenging activity of edaravone and its related derivatives

The experimental and theoretical study for evaluation of scavenging activity of edaravone (S1) and related derivatives, such as antipyrine (S2), dipyrone (S3), and phenylbutazone (S4), was carried out against DPPH and ABTS radicals. Structure–activity relationship study was performed using quantum chemical calculations at the DFT/B3LYP level of theory along with the 6-31G* basis sets. S1 and S4 are more effective scavengers against DPPH and ABTS. We observed little effects of S2 and S3 at several concentrations against these two free radicals. The calculations of HOMO, ionization potential, and bond dissociation energy confirmed that a hydrogen transfer is more preferential than an electron transfer. The radical stability of these compounds is related with spin densities. In accordance with experimental and theoretical results, edaravone is more active than phenylbutazone as scavenging drug.