Antioxidants provide protection against oxidative damage from reactive oxygen species, such as superoxides, hydroxyl radicals, hydrogen peroxide (see here). Biological compounds that provide such protection include substances, such as vitamin A, vitamin C, and vitamin E, uric acid, glutathione and enzymes, such as superoxide dismutase, catalase, glutathione peroxidase. Many antioxidants act by scavenging reactive oxygen molecules or by chemically reducing oxidized compounds.