HISTORY OF ANTIOXIDANTS
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A good approach to understand the true meaning of antioxidants in nutrition, not to mention the chemistry and biology can be to trace their history and the evolution of scientific thought that has highlighted the possible benefits and has been also the basis of undue exaggeration.
Antioxidants have been used for the first time in the nineteenth century in the rubber industry, when it was observed that some molecules, identified empirically, could slow the degradation and allow optimization of the process of vulcanization. Today we know that the production and use of rubber reactions take place involving free radicals and oxygen and antioxidants are still a useful tool in the hands of those who need to optimize the performance of our tires.
In the twentieth century antioxidants are then entered in the arsenal of the emerging food industry, as a key tool to curb the oxidative degradation of stored food. In that regard, it must be said that, since at that time known mechanisms of oxidation nor nor antioxidant effect, the connotation of "antioxidant" could only be empirical, grouping any compound or procedure that led to the result of slow degradation and rancidity. This has resulted in an inaccuracy semantics which often leads today to a different definition of antioxidant between chemists, biologists and food technologists.
If also did not know the free radicals, was known already at the end of the eighteenth century that oxygen, had an extremely important role for life, but also for degradation of biological material.
The most significant demonstration of the role in modern biology radical oxidation is given in the early 50's when in Buenos Aires Gerchman Rebecca and Daniel Gilbert found that the toxic effect of radiation was greatly enhanced by the presence of oxygen.
It emerged that once the concept that ionizing radiation has produced a free radical (molecule or atom with an unpaired electron in an orbital external) this can start a chain of oxidative reactions involving oxygen.
The theory then led to a significant corollary on the role of antioxidants: if the oxidative reactions are chain, one molecule that it intercepts the radical initiator or propagator, prevents the entire chain. It follows that only the reactions radicals that trigger chains may be the subject of a functionally valid inhibition by antioxidants: a concept that, although simple, is today very often forgotten.
In terms of antioxidants, a milestone in the evolution of knowledge is the discovery of Albert Szent-Györgyi, in the thirties, which, starting from the study of the reasons dell'imbrunimento apples, discovered vitamin C. The same researchers also studied the antioxidant effect of polyphenols found in plants and proposed a function vitamin (vitamin P) but could not withstand the criticism of the absence of deficiency syndrome, as fundamental to the definition of a function vitamin.
The cultural boundary was beginning to be quite defined in 50-60 years: it was known that breathing (which is a form of controlled combustion) required oxygen activation and that breathing could generate free radicals. On this basis, supplemented by observations of acute medical and pathophysiological, Denim Harman proposed the free radical theory of aging: if we use oxygen to convert our energy, we can not escape its toxicity which slowly deteriorates there. The 'sharpness of the proposal has been confirmed in experimental biology, it is now generally accepted that the maximum health potential of a species is determined largely, though not entirely, the ability to defend against oxidation. The theory is tested on small animals that actually live longer when more protected from oxidation, but, unfortunately, the story is much more complex in higher animals, including humans.
This collection of information has stimulated the 70 at the end of the last century, a huge amount of studies on the mechanisms radicals, their biological consequences and mechanisms of defense. In this regard have been described enzymatic antioxidant defense systems-those that are far more important-and it is made clear what should be done is a natural antioxidant that acts as a "free radical scavenger" and how to do it. The 'scientific information is then available today to interpret phenomena from the cellular level to that of quantum mechanics. But what is the medical and nutritional aspect of it all?
The first answers can not be that epidemiology in recent years has seen an explosion of meaning, quality and therefore of relevance. In practice, epidemiological studies of various kinds agree that "taking antioxidants in the diet is good" with respect to the reduction of risk of chronic degenerative diseases-mainly atherosclerosis and possibly reduce the risk of cancer. The syllogism that were due to the mechanisms of chemical reactivity of oxide-reductive antioxidants was then supported by a significant number of studies in vitro or cellular models showed different effects of different molecules-generally-polyphenols.
A more careful examination, however, concentrations obtainable in the body compared to those necessary to obtain an increase in antioxidant defense seems to exclude any realistic in vivo antioxidant effect of different dietary polyphenols. In practice, the only food antioxidants that reasonably can have an effect in vivo antioxidant are Vitamin C and Vitamin E. Their deficiency syndrome, however, is typical dell'avitaminosi and certainly not what you would expect from a deficiency of antioxidant defense. Not only that, but the intervention studies with antioxidants (mainly vitamin E) did not produce positive results than conclusive aging and chronic diseases .... So what?
The apparent contradiction reasonable answers are essentially two: a) I am not much of a diet antioxidants "do well" as a diet that contains them as a whole.b) Some (or many) dietary antioxidants may have effects at very low concentrations in the body, but this is independent of the antioxidant.
Both mechanisms have a certain reasonableness scientifically defensible. The wholesomeness of the diet as a whole, premise optimization of quantity and the relationship between the nutrients, also foresees to minimize the contribution of oxidized fats or very oxidizable. In preventing this, they can not play a key role antioxidants in food or anyway the meal as a whole, and that they do their job, preserving, cooking and digestion, when the extent of absorption and bioavailability has no relevance.
On 'other side, it is now shown that many natural substances of polyphenolic nature, and functionally antioxidants, may act by modulating the expression of genes, a mechanism that little or nothing to do with transitions oxide-reductive typical antioxidant effect . The acquisition of this type of information is in its infancy, being supported by complex expression analysis today only possible as a result dell'elucidazione genome. In other words phenolic antioxidants food regulatory elements are configured as "nutrigenomics," to use a practical how ugly neologism.
Among the effects of regulation of cellular response highlighted so far, it is recalled increased resistance to apoptosis (controlled cell death), a decreased reactivity to cellular insults of various kinds, and, sometimes, an increased ability to repair the biological damage. In 'together, the changes in gene expression, for the recruitment of dietary polyphenols, is compatible with a greater resistance to the onset of chronic degenerative diseases that they see as a pathogenetic increased cellular response to an insult of various kinds.
Fulvio Ursini
Department of Biological Chemistry
Universita 'di Padova
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