Antioxydant

An antioxydant is a molecule which decreases or prevents the Oxydation other chemical substances.

Oxidation belongs to a Réaction of oxydoreduction which transfers from the electrons of a substance towards an oxidising agent. This reaction can produce free radical which involve destroying chain reactions. The antioxydants are able to stop these chain reactions while oxidizing with the free radicals and thus destroying their action. These properties are much in the families of the Thiol S and the phenol S.

Although the reactions of oxidation are necessary to the life, they can also be destroying: the plants and the animals use and produce many antioxydants to protect themselves, the such Glutathion, the Vitamine C and the Vitamine E, or Enzymes like the Catalase, the Superoxyde dismutase and some Peroxydase S. a deficiency or an absence of production of antioxydant enzymes involves a oxydative stress which can damage or destroy the cells.

The oxydative stress was blamed in the Pathogénèse of many human diseases, the use of antioxydants in Pharmacologie thus is studied much in particular to treat the cerebral vascular accidents and the neurodégénératives diseases. However, it is not known yet if the oxydative stress is the cause or the consequence of these diseases. The antioxydants are also important ingredients of the food complements with an aim of maintaining health and of preventing certain diseases, like the Cancer or the coronary diseases. Even if studies suggest that the antioxydant complements are beneficial with health, of broad clinical studies did not find to them advantages particular during the tests. Moreover, one excess of supplements (or complements) out of antioxydants can sometimes have negative effects.

The antioxydants are used also much by industry like conservatives for the food, the cosmetics, or to preserve the rubber or the gasoline.

History

The antioxydant term (one says sometimes antioxidant ) in the beginning was used to indicate the chemical substances which prevent the reactions with oxygen. At the end of the 19th century and at the beginning of the 20th century the properties of antioxydants were largely studied for their use in the industrial processes in order to reduce for example the Corrosion metals, the vulcanization of the rubber and the Polymérisation of the fuels in the engine spark-ignition .

In biology, the first research on antioxydants related to the reduction of the oxidation of the unsaturated fatty-acids, causes Rancissement. The antioxydant activity was easily measured by locking up greasy substances in airtight containers with oxygen, then by checking the rate of absorption of this last. However, it is not that with the identification of the vitamins has, C and E which the importance of antioxydants in biochemistry of the living organisms appeared.

The possible mechanisms of antioxydants were studied as from the moment when it was understood that an antioxydant substance was to be itself easily oxydable. Research on the action of the vitamin E in the limitation of the oxidation of the Lipide S showed its role in the elimination of the molecules containing an active oxygen atom before the latter do not attack the cells.

Properties

From a chemical point of view, an antioxydant is only one made up reducer: it thus will be able to react with an oxidant to neutralize it. The antioxydants thus will reduce the radical free so dangerous for the organization because them very high capacity oxidizing. Thus, the antioxydants present in food protect the organic molecules, for example greases or l' DNA , of oxidation and seem to play a protective part against carcinogenesis.

Use

The antioxydants are used:

in chemical industry - for example to avoid the hardening of the rubber - or in Metallurgy, to protect the metals from the Oxidation;
in agro industry Food surface - for example to avoid the rancidity of the greasy substance.

Antioxydants in the food

The most known antioxydants are the ß- Carotène (provitamins A), the Ascorbic acid (Vitamine C), the Tocophérol (vitamin E), the Polyphénol S and the Lycopène. Those include the Flavonoïde S (very widespread in the vegetable ), the Tanin S (in the Cacao, the Café, the The, the Raisin, etc), the Anthocyane S (in particular in the red fruits) and the acids phenolic (in the Céréale S, the Fruit S and the Légume S).

Example of the The

Fruits rich in antioxydant

The Fruit S are rich in antioxydants, in particular those known as reds, the such Airelle S, because of combined presence of vitamin C and polyphenols. Antioxydant capacity of a food, i.e. its capacity to resist the Oxidation, is expressed in units Orac ( radical Oxygen absorptance capacity : this value measures the capacity of food to neutralize the radical peroxyle):

It is advisable to add to this fruit list the richest species, following the example tomato, out of lycopene (tetraterpene, red and powerful pigment liposoluble antioxydant of the family of carotenoids), namely: the water melon, the guava, the papaw… which lines up among the fruits having the strongest antioxydant concentration.

The mangoustan - Fruit of the Mangoustanier - is considered to contain powerful natural antioxydants, whose at least 40 Xanthone S. the bark of the fruit contains in particular vitamins, catéchines, stilbenes and xanthones, of which alpha-mangoustin.

Vegetables rich in antioxydant

The Tomato, the cress, the garlic, the curly kale, the spinach, the Asparagus, the Brussels sprout, the germ of alfalfa, the Broccoli, the Beet and the red Poivron are the vegetables having the strongest antioxydant concentration.

One allots the antioxydant character of this food to their rich person content of Vitamine C, Caroténoïde S (of which the Lycopène S), phenolic Flavonoïde S, compounds, Terpénoïde S and Resvératrol.

At the time of the Cooking, certain antioxydants such as the vitamin C are inactivated, whereas others change to become more active or more easily absorbable by the digestive system. It is the case of the Lycopène S of tomato. Indeed, the cooking of tomato increases the biodisponible quantity of lycopene, heat releasing it from the cells of tomato. Thus, there are approximately four times more biodisponible lycopene in the tomato sauce than in fresh tomato!

Family of antioxydant additives

The many antioxydant additives used in agribusiness industry are divided into eight families:

ascorbic acid (E300), ascorbates of sodium (E301), calcium (E302), acid diacétyl 5-6-1-ascorbic (E303), acid palmityl 6-1-ascorbic (E304);
acid citric (E330), citrates of sodium (E331), potassium (E332) and calcium (E333);
acid tartaric (E334), sodium tartrates (E335), potassium (E336) and of sodium and potassium (E337);
butylhydroxyanisol (E320) and butylhydroxytoluol (E321);
gallates of octyl (E311) or dodécyle (E312);
lactates of sodium (E325), potassium (E326) or calcium (E327);
lecithins (E322);
natural tocopherols (E306), alpha-tocopherol of synthesis (E307), gamma-tocopherol of synthesis (E308) and delta-tocopherol of synthesis (E309).

Antioxydants and health

Many studies tried to study the impact of the catch of antioxydant food supplements in the prevention of various diseases. The results of these studies are unmatched.
In February 2007, méta-analyzes bearing on all the randomized tests indexed in the literature and using antioxydants in primary and secondary prevention nevertheless concluded that the supplements (or complements) out of antioxydants do not make it possible to decrease mortality . The unmatched results could be explained by the origin of antioxydant: the natural chemical forms, which exist in nature (food) would be the only effective ones. Antioxydant an excess, in particular synthetic, would be harmful. Taking the example of the vitamin E, generally proposed in the supplements in the alpha-tocopherol shape, it is noted that in nature, it is more often in the form of béta-tocotrienol. From where possible skews in the studies.

JAMA 2007 méta-analyzes

A Danish and Serb team with published in February 2007 méta-analyzes of all the randomized tests using of antioxydants in primary prevention and secondaire.
All the studies randomized in the adults comparing the Beta-carotene, the Vitamine has, the Vitamine C, the Vitamine E or the Sélénium, is in a way isolated or combined with a placebo or l´absence d´intervention were included in this analysis what represents 68 studies randomized bearing on 232.606 participants.

The results of this méta-analyzes do not show d´effet significant antioxydant supplements on mortality (RR = 1,02, IC₉₅ = 0,98-1,06). The analyzes in multivariate méta-regression showed that the studies having weak skews and selenium (RR = 0,998, IC₉₅ = 0,997-0,9995) were significantly associated with mortality. In 47 of the studies with weak bearing skew on 180.938 participants, the supplements by antioxydants increased to a significant degree mortality (RR = 1.05, IC₉₅ = 1,02-1,08). After exclusion of the tests relating to selenium, beta-carotene (RR = 1,07, IC₉₅ = 1,02-1,11), the vitamin has (RR = 1,16, IC₉₅ = 1,10-1,24) and the vitamin E (RR = 1,04, IC₉₅ = 1,01-1,07) in an isolated or combined way increased to a significant degree mortality.

The authors thus conclude that:

the Vitamin C and the Sélénium n´avaient not d´effet significant on mortality;
the Beta-carotene, the Vitamine has and the Vitamine E could increase mortality.

This study does not take into account if the antioxydant supplements taken are natural or synthetic extracts.

Study SU.VI.MAX

As of the years 1980, one considered a relation between the consumption of Fruit S and Légume S and a protective effect against the carcinogenesis. This assumption, inspired in particular by the beneficial effects of the Mediterranean Mode (more precisely of the mode crétois), having been confirmed by a score of studies, one supposed that the antioxydant effect of certain food was in the beginning.

During eight years, French study SU.VI.MAX (Supplements in vitamins and minerals antioxydant) followed more than 13.000 elderly from 35 to 60 years. Its results show that the contribution of antioxydants, with amounts comparable with those of a healthy Alimentation, cause a drop in of more than 30% the risk of Cancer and the mortality of the men. On the other hand, no difference could be highlighted among women, perhaps because they consume more fruit and vegetables that the men or that they smoke less.

These results encourage to eat many fruit and vegetables, sources of antioxydants but as of rock salt and Vitamine S. One estimated as 9% of cancers could be avoided in France thanks to a daily consumption of five portions of fruit and vegetables, a portion corresponding to a large fruit, 100 G of crudenesses or 200 G of cooked vegetables.

Recent American studies showed that the antioxydants taken in medicamentous form do not have as many effects as those taken in the natural food . Of or interest of a healthy food and, probably, antioxydant food complements extracted directly from existing products in nature, since only the chemical shapes of food are effective.

References

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