Free radicals and antioxidant nutrients

A compound that loses or gains a single electron, and thus has an unpaired electron in 

To show that a compound is a free radical, its chemical formula is shown with a dot ( ) to represent the unpaired electron — for example, the hydroxyl radical is OH. 

If two radicals react together, each contributes its unpaired electron to the formation of a new, stable bond. This means that the chain reaction, in which reaction of radicals with other molecules generates new radicals, is stopped. This is quenching of the chain reaction, or quenching of the radicals. As radicals are generally so short-lived, it is rare for two radicals to come together to quench each other in this way. 

Radicals may interact with any compounds present in the cell, and the result may be initiation of cancer, heritable mutations, atherosclerosis and coronary heart disease or autoimmune disease. The most important, and potentially damaging, such interactions are  

1 With DNA in the nucleus, causing chemical changes in the nucleic acid bases (section 9.2.1) or breaks in the DNA strand. This damage may result in heritable mutations if the damage is to ovaries or testes, or the induction of cancer in other tissues. Although much damage to DNA is detected and repaired by the DNA repair system in cells, some will escape detection. 

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