What is Antioxidant and what does it do?

What makes so many phenols have antioxidant properties?

• http://extremelongevity.net/2013/01/21/new-synthetic-phenol-antioxidant-extends-lifespan/ also, lots of fruits and veggies have antioxidant phenols too

• Answer:

  Reactive radical species are thought to be deactivated by phenols and polyphenols through an H-atom abstraction process. R* + PhOH -> RH + PhO* The produced phenoxyl radical is stabilized by resonance and, in more complex molecules, by intramolecular H-bonding. It is the stability of the phenoxyl radical that makes phenols good at quenching radical species. The phenoxyl radicals are usually destroyed by dimerization.