Definition of free radicals and other reactive oxygen species

Free radicals are atoms or molecules with unpaired electron(s). Free radicals are generally highly reactive but some of them may be stable for long time. Examples of reactive free radicals are superoxide, hydroxyl radical, protein radical and nitrogen dioxide. Vitamin E (tocopheroxyl) and vitamin C (dehdroascorbate) are examples of stable free radicals. Among the most powerful oxidants are perooxynitrite, nitrogen dioxide, and nitric oxide.

Reactive oxygen species refers to oxygen containing free radicals and non free radical active molecules. Reactive oxygen species that are not free radicals include hydrogen peroxide, singlet oxygen, and lipid hydroperoxide.

Benefits of free radicals and other reactive oxygen species


Free radicals and other reactive oxygen species are produced in all living organisms and have biological advantage. Evidences from multitude researches on free radicals and reactive oxygen species suggest that they play important roles in signal transduction, sensing of oxygen tension and regulation of functions controlled by oxygen concentration. They are essential in synthesis of energy and essential molecules. They are also involved in boosting our immune system.

Synthesis of free-radicals in our body is higher during intensive physical exercise and with certain diseases such as diabetes.

Side effects of free radicals and reactive oxygen species


When free radicals and other reactive oxygen species accumulate in the body they cause damage on cells, DNA, lipid, sugar, and protein. The damage caused by free radicals and reactive oxygen species, in plants and animals, could lead deterioration of foods, cell membrane dysfunction, protein modification, enzyme inactivation, break of DNA strands, brain damage and dementia. Free-radical induced oxidative damages may be precursors to aging and diseases such as cancer, heart disease, diabetes mellitus, atherosclerosis, hypertension, sleep apnea, brain damage and dementia related diseases such as Alzheimer’s disease and Parkinson’s disease.

Free radical theory of aging

Free radical theory of aging states that oxidative damage induced by free radicals is to large extent the cause to age-related degenerative processes.

Antioxidant, and free radicals and other reactive oxygen species

Antioxidants are among the variety of defense mechanisms against oxidative stress induced by free radicals. Examples of well studied free radical-scavenger antioxidants are vitamin E, vitamin C, flavonoids, chlorophyll and carotenoids. Growing number of researches on the role of antioxidants suggest that there is strong association between high intake of antioxidants and low incidence of diseases linked with free radicals.


Antiooxidant: Definition, role against free radicals and food sources
List of foods high in antioxidant content
Coenzyme A: Antioxdiant activity and health benefit
Flavnoids: Antioxidant activiity
Chlorophyll: Its antioxidant activity and health benefit?
Blueberry antioxidant
Antioxidant and its anti-aging effect
Antioxidant and its benefit against cancer

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