How Antioxidants Work
~ October 1997 No.17 ~
Everything from tea to carrots to vegetable oils are being promoted as being good for your health. This is because these and many other foods contain antioxidants. Vitamin A, C and E (alpha-tocopherol) capsules are being consumed in larger and larger quantities because of their well established antioxidant properties.
Oxidation of a wide range of chemical compounds and the production of radicals at the cellular level are believed to be involved in the cause of many cancers and may also be important factors causing cardiovascular disease. This is why there is so much interest in antioxidants. But how exactly do antioxidants work?
The key role played by antioxidants in the body is their ability to react with radicals. When this happens the destructive properties of the radical is eliminated. A free radical is a chemical compound that contains one or more unpaired electrons. Radicals can be produced by exposure to energy such as radiation or may be the product of incomplete reactions in the cells that produce electrons that have escaped . The step that produces a radical is called the initiation step. Radicals are usually represented in chemical formula by a single dot. Below are three examples of initiation steps that illustrate the production of radicals.
In nature electrons are usually paired. In radicals they are not, and so radicals generally are more reactive than non-radicals. Because they are reactive, radicals search out ways of pairing up their odd electron. In their haste to pair up their electron, radicals often attack nearby chemical compounds. These chemical compounds may be involved in important enzyme reactions, may be components of cell walls or may be part of a DNA molecule. If their chemical structure is changed, their function in the body may be lost and the result can be disease or infection. This process is usually long term, but more and more evidence is pointing to the benefits of reducing oxidative damage in body tissue.
A radical can donate its odd electron to another molecule, it can rob an electron from another nearby molecule or it can combine with another radical. When two radicals combine this is called a termination step.
If the initial radical donates or steals an electron, a second radical is produced which can then in turn react. This can continue in a series of propagation steps, until termination occurs.
Cell membranes are particularly sensitive to radical reactions, since cell membranes are composed of fatty acids which can easily form peroxyl radicals. Fortunately alpha-tocopherol is also located in cell membranes. Electron transfer from the peroxyl radical to alpha-tocopherol restores the fatty acid, thus retaining the cell membrane structure and function. The tocopherol radical that is formed is more stable because of its chemical structure. Tocopherol is less reactive than other radicals and so it doesnt immediately try to rob an electron from nearby molecules . It has time to move to the surface of the cell membrane where it can pick up an electron. It becomes alpha-tocopherol again and can return to react with other membrane radicals.
It is the ability of alpha-tocopherol to pick up and transport electrons that makes it an anitoxidant. All antioxidant agents work in this way to protect the cells in the body from the damage of radicals.
Presenter: James A. Jackson, MT (ASCP). Ph.D -Sep 15, 2011
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