Antioxidants are chemicals that can clean up rogue free radicals in the body. In doing so, they remove potentially harmful free radicals from circulation. However, not all free radicals are bad, and not all antioxidants are good.
Manganese is one mineral you are unlikely to have to supplement in your diet. It is involved in many enzyme reactions as it is a co-factor required by the enzyme. It is involved in removing free radicals as well as regulation of sugar release from muscle and liver tissue.