Vitamin antioxidant role

Plants represent a very important role in human nutrition, due to the large quantities of proteins, carbon hydrates, lipids, vitamins, antioxidants and mineral salts that its can supply. Sometimes the nutritional aspect can be associated with the flavour and fragrance of the extracts producing a high value products. In recent years one can observe an increase in research for natural sources, in particular from plant matrices, of additives with application in the food, cosmetic and pharmaceutical industries. 

For a long time, it was considered that, unlike the other vitamins, vitamin E had no specific functions rather it was the major Upid-soluble, radicaltrapping antioxidant in membranes. Many of its functions can be met by synthetic antioxidants however, some of the effects of vitamin E deficiency in experimental animals, including testicular atrophy and necrotizing myopathy, do not respond to synthetic antioxidants. The antioxidant roles of vitamin E and the trace element selenium are closely related and, to a great extent, either can compensate for a deficiency of the other. The sulfur amino acids (methionine and cysteine) also have a vitamin E-sparing effect. 

The best-established function of vitamin E is as a lipid-soluble antioxidant in plasma lipoproteins and cell membranes. Many of the antioxidant actions are unspecific, and a number of synthetic antioxidants have a vitamin E-sparing effect. There is considerable overlap between the antioxidant roles of vitamin E and selenium (Section 4.3.2). 

Al-Malaika, S. Issenhuth, S. Burdick, D. The antioxidant role of vitamin E in polymers. V. Separation of stereoisomers and characterization of other oxidation products of dl-a-tocopherol formed in polyolefins during melt processing. J. Anal. Appl. Pyrolysis 2001, 73, 491-503. 

Vitamin activity in foods and food products serves as an example where typical problems arise with traditional liquid solvent extraction and then where SFE has been used to address these concerns [30]. In addition to the routine assay of food products, there is a considerable amount of research being conducted on the role of carotenoids and xanthans as antioxidants in the human body. This antioxidant-role may address many health concerns such as aging and various diseases. The "friendly-extracting-environment" of SFE has some merit of consideration for such studies, particularly with regard to the lesser possibility of oxidation of the analytes during the sample preparation step. 

Tissue accumulation of a-tocopherol in vitamin E supplemented animals appears to occur in a dose-dependent manner. Since a-tocopherol is consumed in performing its antioxidant role, the strategy for gaining maximum shelf-life is to maximize the concentration of vitamin E present in tissue at slaughter. Arnold et al. (1992b) have established that beef muscle can become saturated with a-tocopherol and that continued supplementation of animals with vitamin E beyond this point yields no added benefit and results in unnecessary expense. 

At intakes above about 100 mg/day the body s capacity to metabolize vitamin C is saturated, and any further intake is excreted in the urine unchanged. Therefore, it would not seem justifiable to recommend higher levels of intake. However, in addition to its antioxidant role (section 7.4.3.5), vitamin C is also important in the absorption of iron (section 4.5.1). This depends on the presence of the vitamin in the gut together with food, and intakes totalling more than 100 mg/day may be beneficial. 

In its antioxidant role, vitamin E also protects vitamin A (and carotene), vitamin C, sulfur-containing enzymes, and ATP from being oxidized, thereby enabling these essential nutrients to perform their specific functions in the body. 

Azzi, A. and A. Stocker. 2000. Vitamin E Non-antioxidant roles. Prog. Lipid Res. 39 231-255. 

The age pigments (lipofuscin), which accumulate with age, aie largely made up of these precipitated Hpid-proteia complexes resultiag from such cross-linking. Vitamin E may function to help prevent formation of these complexes. The metaboHc role of antioxidants (qv) such as vitamin E in animal tissues, however, remains quite controversial. 

The structure of vitamin E in its most active form, o-tocopherol, is shown in Figure 18.38. a-Tocopherol is a potent antioxidant, and its function in animals and humans is often ascribed to this property. On the other hand, the molecular details of its function are almost entirely unknown. One possible role for... 

A specific role for vitamin E in a required metabolic function has not been found. In addition to its direct antioxidant effects, a-tocopherol has been reported to have specific molecular functions. 

Some sprays include vitamins such as tocopherols (vitamin E) or panthenol, which is metabolized in the skin to become pantothenic acid, a B vitamin. Since hair does not metabolize ( It s dead, Jim ), these sprays perform the functions of antioxidants (tocopherols). In other words, they add shine and moisture (panthenol) rather than perform their normal vitamin roles. Moisture helps prevent damage during combing. 

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