antioxidant

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antioxidant

 [an″te-ok´sĭ-dant]
a substance that in small amounts will inhibit the oxidation of other compounds.

an·ti·ox·i·dant

(an'tē-oks'ĭ-dănt),
An agent that inhibits oxidation; any of numerous chemical substances including certain natural body products and nutrients that can neutralize the oxidant effect of free radicals and other substances.

Free radicals, formed in the course of normal cellular respiration and metabolism, and more abundantly under the influence of certain environmental chemicals and sunlight, have been inculpated in various types of tissue damage, particularly those involved in atherosclerosis, the aging process, and the development of cancers. A free radical is any atom or molecule that has 1 or more unpaired electrons and is therefore highly reactive, seeking to acquire electrons from other substances. Free radicals are normally scavenged from tissues by the antioxidant enzymes superoxide dismutase and glutathione peroxidase. Ubidecarenone (coenzyme Q10) is also thought to act as an antioxidant in mitochondrial respiration reactions. In addition, a number of nutrient substances, vitamins, and minerals have been shown to contribute to antioxidant functions, generally by serving as cofactors or coenzymes. These include selenium beta-carotene, and vitamins C and E. It has been postulated that an imbalance between the production of free radicals and natural antioxidant processes may be a major causative factor in aging and in many chronic and degenerative disorders, and some researchers have speculated that antioxidant nutrients may have a role in disease prevention. Oxidation of low-density lipoprotein cholesterol does indeed seem to be responsible for foam cell formation in the genesis of atherosclerotic plaques. In addition, free radicals have been shown to damage DNA in ways that can culminate in malignant change. Oxidations also occur in many beneficial processes, however, including chemotaxis of cells with immunologic functions, phagocytosis, clotting mechanisms, and apoptosis. Moreover, antioxidants do not exert their effects in only one way, but can act during initiation or propagation of reactions at a variety of intracellular sites, and in some circumstances can be prooxidant. Claims that vitamins and other nutrients, when taken in massive doses, can prevent heart attack or cancer or retard aging are not based on scientific evidence. Although a high intake of antioxidants from food sources appears to offer some health advantages, there is at present no unequivocal evidence that any antioxidant nutrient, when taken in excess of normal dietary amounts, has value in the prevention or treatment of cardiovascular disease, cancer, or any other abnormal process except such as may be associated with frank nutritional or vitamin deficiency. A controlled, double-blind, randomized study of antioxidant supplementation in more than 20,000 people at risk of coronary artery disease found no effect whatsoever on all-cause mortality, cardiovascular mortality, nonfatal myocardial infarction, stroke, or cancer incidence. A controlled trial of beta-carotene and retinol not only failed to show any benefit but was aborted when statistics showed large increases in the risk of death from lung cancer and cardiovascular disease.

antioxidant

/an·ti·ox·i·dant/ (-ok´sĭ-dant) something added to a product to prevent or delay its deterioration by the oxygen in air.

antioxidant

(ăn′tē-ŏk′sĭ-dənt, ăn′tī-)
n.
A substance that inhibits oxidation, especially one, such as vitamin E, vitamin C, or beta carotene, that protects cells from the sometimes damaging effects of oxidation.

antioxidant

[-ok′sidənt]
a chemical or other agent that inhibits or retards oxidation of a substance to which it is added. Examples include butylated hydroxyanisole and butylated hydroxytoluene, which are added to foods or the packaging of foods containing fats or oils to prevent oxygen from combining with the fatty molecules, thereby causing them to become rancid.

antioxidant

Any agent—e.g., vitamin A, vitamin C, selenium—which is capable of reducing highly histotoxic oxygen-reduction products and reactive oxygen species (e.g., hydroxyl radical), which derive from superoxide anion (O2-) and H2O2, the univalent and bivalent reduction products of oxygen, and are generated during the normal intermediary metabolism of the respiratory chain. Other antixodants include glutathione, alpha-tocopherol (vitamin E) and bilirubin.

antioxidant

Nutrition Any agent–eg, vitamins A, C, and E, selenium, and others, that is capable of reducing highly histotoxic O2 reduction products and reactive O2 species—eg hydroxyl radical, which derive from superoxide anion–O2·– and H2O2, the univalent and bivalent reduction products of O2, generated during the normal intermediate metabolism of the respiratory chain; other antixodants include glutathione, α-tocopherol–vitamin E, bilirubin. See Catalase, Ceruloplasmin, Free radical, Glutathione, Peroxidase, Superoxide dismutase, Transferrin.

an·ti·ox·i·dant

(antē-oksi-dănt)
Any substance that may prevent organ damage by scavenging free radicals, including catalase, glutathione, peroxidase, superoxide dismutase, and vitamins A, C, and E.
See also: free radical

Antioxidant

Any substance that reduces the damage caused by oxidation, such as the harm caused by free radicals.
Mentioned in: Smoking

oxidative stress 

A term used to describe the effect of oxidation in which an abnormal level of reactive oxygen species (ROS), such as the free radicals (e.g. hydroxyl, nitric acid, superoxide) or the non-radicals (e.g. hydrogen peroxide, lipid peroxide) lead to damage (called oxidative damage) to specific molecules with consequential injury to cells or tissue. Increased production of ROS occurs as a result of fungal or viral infection, inflammation, ageing, UV radiation, pollution, excessive alcohol consumption, cigarette smoking, etc. Removal or neutralization of ROS is achieved with antioxidants, endogenous (e.g. catalase, glutathione, superoxide dismutase) or exogenous (e.g. vitamins A, C, E, bioflavonoids, carotenoids). Oxidative damage to the eye, particularly the retina and the lens, is a contributing factor to age-related macular degeneration and cataract.

an·ti·ox·i·dant

(antē-oksi-dănt)
An agent that inhibits oxidation; one of many chemical substances including some natural body products that can neutralize the oxidant effect of free radicals and other substances.

antioxidant

a substance that in small amount will inhibit the oxidation of other compounds. Used in feeds and foods to prevent rancidification of polyunsaturated fats.

Patient discussion about antioxidant

Q. What are “antioxidants”? and what do they do? I’ve been hearing about antioxidants for quite some time now, they are supposedly help to keep us younger. What do they do and is it true?

A. When every biological system works- it creates oxidants. These are materials that are very active and they “look for” something to react with. So when you eat (an example) there are a lot of oxidants created. they move around in the colon and they usually react with colon cells, thus destroying them. This also happens while breathing, cell metabolism and a lot of biological processes. Antioxidants counteract these free oxidants and stop their harmful reaction.

More discussions about antioxidant
References in periodicals archive ?
During the decomposition of allicin, sulfenic acid is formed, which acts as a free radical scavenger.
Melatonin, ascorbate, and vitamin E (Trolox), all of which are free radical scavengers, markedly inhibited the formation of 8-OH-dG in a concentration-dependent manner.
Examples include acidic materials such as certain nonblack fillers and fatty acids and antioxidants which function as free radical scavengers, thereby reducing peroxide cure efficiency.
Free radical scavengers neutralize free radicals to help prevent damage to the body's cells which has been linked to aging, weakened immune systems and most chronic disease processes, including heart disease, diabetes, stroke, Alzheimer's disease, arthritis, and DNA damage leading to mutations and some types of cancer.
PhytoCellTec Solar Vitis is based on the stem cells of the Gamay Teinturier Freaux grape containing Anthocyanins, which are powerful antioxidants and free radical scavengers.
TM ](Antioxidants, Free Radical Scavengers & Bioflavonoids, Multiple Oil and Water-soluble Vitamins with their Coenzymes and much more) help reduce itchiness, maceration and inflammation of the skin in the ear canal.
The ingredients in this novel combination act synergistically on multiple levels as antioxidants, free radical scavengers, and growth factor stimulators to prevent hair loss and to enhance overall hair follicle and scalp health.
New drug classes such as endopeptidase/endothelin antagonists, vasopressin-2 inhibitors, brain natriuretic peptide-targeted molecules and free radical scavengers have emerged.