The free radicals of most concern in the bio-medical field are the free radicals derived from oxygen, they are called reactive oxygen species. Specifically, there are the superoxide anions, the peroxides including hydrogen peroxide, and the hydroxyl radicals.
Free radicals are unstable and highly reactive molecules that are produced in the body during normal oxygen metabolism. Free radicals play both helpful and harmful roles in the body. Free radicals steal electrons from other substances in order to become stable. In so doing, the free radicals oxidize those other molecules. When the quantity of free radicals greatly exceeds the quantity of antioxidants, the free radicals can cause chain reactions and can cause much cell and tissue damage.
Free radical is the name for the broad category of atoms and molecules with unpaired electrons. The more specific category of free radicals that is of special interest in human health is the category of reactive oxygen species, which are free radicals derived specifically from oxygen: superoxides, peroxides, and hydroxyl radicals.Coenzyme Q10, vitamins C and E, and glutathione peroxidase are some of the notable antioxidants that protect the cells and tissues against oxidative stress and damage.