Aspects physico-chimiques des espèces réactives de l'oxygène

Knowledge of thermodynamic (reduction potentials) and kinetic (rate constants) properties of ROS allows to draw up a rigorous overview of the chemical reactivity of these species. Hydroxyl free radicals (°OH) are powerful oxidants (very toxic species) which attack all the biomolecular targets (DNA, proteins, lipids…), giving other free radicals localized on the targets. Superoxide free radicals (O 2 °- ) have a more graduated reactivity, since they don't directly react with biological molecules. However, some toxicity would be attributed to them via secondary radicular reactions. Other free radicals (of peroxyl RO2 ° and alkoxyl RO° types), belonging also to the ROS family, contribute by enhancement to oxidative stress.