HYDROXYL RADICAL SCAVENGING ACTIVITY OF COMPOUNDS WITH PHARMACEUTICAL INTEREST - A QUANTITATIVE-ANALYSIS BY ESR SPECTROSCOPY

Under various pathological conditions, the natural defense mechanisms against oxidative stress are not sufficient to prevent radical-induced injury. Then it becomes necessary to develop free radical scavengers and antioxidant therapies. In order to evaluate the antioxidant capacity of different substances, Electron Spin Resonance (ESR) and the spin trapping technique have been used to develop in vitro tests. Hydroxyl radicals have been generated by Fenton's reaction and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) has been used as spin trap. The hydroxyl radical scavenging efficiency of the tested substance was quantified by an IC50 value representing the concentration necessary for 50% diminution of the ESR signal Intensity. The influence of the incubation time, the DMPO-OH adduct stability and the solvent used for solubilization have been investigated. The scavenging activity (IC50) of the tested compounds varies from 2.94x10(-5) M to 1.35x10(-2) M for ascorbic acid and arbutin, respectively.