theory of aging

The free radical theory of aging states that organisms age by the multiplication of lesions related to the accumulation of free radicals in cells.

A "free radical" is an atom or molecule with a single unpaired electron in its outer layer. While some free radicals, such as melanin, are chemically inert, most free radicals present in organisms are highly reactive. In most biological structures, lesions related to the presence of free radicals are closely associated with the oxidation process. Antioxidants are reducing agents that limit the action of free radicals in these structures by passivating them.
Strictly speaking, radical theory, as originally stated by Denham Harman in the 1950s, 5 only concerns superoxide radicals (O2-), but its author extrapolated the theory in the 1970s to mitochondrial syntheses of derivatives. Oxygen reagents6 and since it includes lesions of other chemically aggressive species such as hydrogen peroxide (H2O2), or peroxynitrite (OONO-).
It has been demonstrated on certain model organisms such as yeasts and Drosophila that the reduction of oxidation-related lesions prolongs life; in contrast, in mice, only genetic alteration blocking the antioxidant barrier on (destruction of SOD1 enzymes), reduces the life span. Similarly, it has recently been observed that in nematodes (Caenorhabditis elegans), the inhibition of the synthesis of the natural antioxidant, superoxide dismutase, increases the life expectancy. The effectiveness of the reduction of the risks of oxidation in the increase of the lifetime therefore remains a controversial question. (Wikipedia)