Primary antioxidants

An antioxidant is a molecule that inhibits the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals which leads the cell to damage or death.

Primary-antioxidants are the chain breaking antioxidants which react with lipid radicals and convert them into more stable products. Primary-antioxidants are essential antioxidant enzymes naturally produced by human body. These internal antioxidant enzymes serve as human body's most potent defense against free radicals and harmful inflammatory reactions.

Primary antioxidant can accept free radicals and further delay the initiation step or interrupt the propagation step of auto-oxidation. Primary antioxidants (AH) can react with lipid and peroxyl radicals converting them into more stable radicals or non-radical products (R• + AH→RH + A•) (RO• + AH→ROH + A•) (ROO• + AH→ROOH + A•).

Superoxide dismutase (SOD), Glutathione Peroxidase (GPx) and Catalase (CAT) are the only known as primary antioxidant enzymes and each one performs reduction of particular ROS. Superoxide radicals are reduced by SOD so that H2O2 and O2 are formed. GPx is the next player in which has a role to reduce H2O2 or organic hydro-peroxides to water and alcohol respectively.
Primary antioxidants