Oxidative stress

Chemists and biologists often define oxidative stress as an imbalance, in particular in biological cells, between the rate of formation and/or concentration of oxygen free radicals (or 'reactive oxygen species') — potent 'oxidizing' (electron capturing) molecules — and their elimination or 'neutralization' by antioxidants — 'reducing' (electron donating) molecules — the imbalance characterized by an excess of the former or a deficiency of the latter, leading to an alteration of a cell's redox state towards the oxidized state.