Free radical

A free radical, or radical, is an atom or molecule with an unpaired electron. The radical is reactive and seeks another electron to pair. Rice-Evans, C. (1999). “Screening of phenolics and flavonoids for antioxidant activity”. In: Antioxidant Food Supplements in Human Health. Academic Press, p. 239–253. 

Many free radicals, are (very reactive or) highly chemical reactive.

In biology
Free radicals are involved in the causes of damage associated with disease development. Examples are hydrogen peroxide, hypochlorite, nitric oxide and nitrogen dioxide. Afzal, M., Armstrong, D. (2002). “Fractionation of herbal medicine for identifying antioxidant activity”. In: Armstrong, D. (Ed.) Methods in Molecular Biology, vol. 186: Oxidative Stress Biomarkers and Antioxidant Protocols, Humana Press Inc.  

The need for antioxidants in people's daily lives is becoming more critical with increased exposure to free radicals. Oxygen is highly reactive and can form free radicals; antioxidants can stabilize or deactivate oxygen free radicals before they attack cells. Pollution, cigarette smoke, drugs, illness, and stress can increase our exposure to oxygen free radicals.Percival, M. (1998). “Antioxidants”. Clinical Nutrition Insights 1/96 Rev. 10/98. http://acudoc.com/Antioxidants.PDF 
 References 

Category:Chemistry