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Antioxidants are chemical substances found in nature. They are part of a group of vitamins, such as vitamin C, vitamin E, vitamin A (beta-carotene), etc., and nutrients like selenium, lutein, and lycopene.
Functions
Oxygen damage (oxidation) to your cells results when there are too many free radicals present inside the body. Researchers surmise that such damage may be partly responsible for the effects of aging and certain diseases. How then does the human body cope? The question led scientists to discover the existence of certain substances in food that may play a role in protecting against such damage. By donating electrons to stabilize and, in effect, neutralize the harmful effects of the free radicals, antioxidants can block this damage.
How they work:
Ultimately, what antioxidants do is to block the process of oxidation by neutralizing free radicals. In doing so, the antioxidants themselves become oxidized. That is why there is a constant need to replenish our antioxidant resources. Antioxidants work in a two-way process. First is the chain-breaking process.
When a free radical releases or steals an electron, a second radical is formed. This molecule then turns around and does the same thing to a third molecule, continuing to generate more unstable products. The process continues until termination occurs – that is, when either the radical is stabilized by a chain-breaking antioxidant such as beta-carotene and vitamins C and E, or it simply decays into a harmless product.
The second process is more on the preventive side.
Antioxidant enzymes like superoxide dismutase, catalase, and glutathione peroxidase prevent oxidation by reducing the rate of chain initiation. This time, instead of waiting for the free radicals to make a long chain of free radicals, antioxidants scavenge initiating radicals and destroy them before oxidation is set in motion. They can also prevent oxidation by stabilizing transition metal radicals such as copper and iron. The effectiveness of any given antioxidant in the body depends on which free radical is involved. It may also depend on how and where the free radical is generated and where the target of damage is. That is why you may find that some antioxidants work well in one particular system but may not protect against free radicals in a completely different system.
Worse still, an antioxidant may even act as a "pro-oxidant" that generates toxic oxygen species in certain circumstances.
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