Antioxidants are compounds that inhibit oxidation. Oxidation is a chemical reaction that can produce free radicals, thereby leading to chain reactions that may damage the cells of organisms. Antioxidants such as thiols or ascorbic acid terminate these chain reactions. A substance that inhibits oxidation, especially one used to counteract the deterioration of stored food products. A substance such as vitamin C or E that removes potentially damaging oxidizing agents in a living organism.