D-a-tocopherol

Fig. 1 Reflectance scan of a chromatogram of 200 ng D-a-tocopherol per chromatogram zone.

No unequivocal unique function for vitamin E has been defined. However, it does act as a hpid-soluble antioxidant in cell membranes, where many of its functions can be provided by synthetic antioxidants. Vitamin E is the generic descriptor for two famihes of compounds, the tocopherols and the tocotrienols (Figure 45—5). The different vitamers (compounds having similar vitamin activity) have different biologic potencies the most active is D-a-tocopherol, and it is usual to express vitamin E intake in milhgrams of D-a-tocoph-erol equivalents. Synthetic DL-a-tocopherol does not have the same biologic potency as the namrally occurring compound. 

TASINATO A D, BOISCOBOINIK D, BARTOLI G M, MARONi p and Azzi A (1995) d-a-tocopherol inhibition of vascular smooth muscle cell proliferation occurs at physiological concentrations, correlates with protein kinase C inhibition, and is independent of its ntioydd ait xo eriie% Proceedings National Academy Sciences USA 92, 12190-4. 

Goodhue, C. T. Risley, H. A. Reactions of vitaminE with peroxides I. Reaction of benzoyl peroxide with D-a-tocopherol in hydrocarbons. Biochem. Biophys. Res. Commurt. 1964, 17, 549-553. 

B. (2005). Ultraviolet B-induced DNA damage in human epidermis is modified by the antioxidants ascorbic acid and D-a-tocopherol. Journal of Investigative Dermatology, 124, 304-307. 

Active analogues and related compounds include dl-a-Tocopherol l-a-toccpherol esters (succinate, acetate, phosphate), and fi, (. c.-tocopherol-,. The principal physiological forms are D-a-tocopherol. tocopheronolactone, and their phosphate esters. 

Tocopherol molecules contain three chiral centers at C-2, C-4, and C-8, making possible eight stereoisomers. Tocotrienols possess only the chiral center at C-2. Naturally occurring a-tocopherol (commonly known as d-a-tocopherol) should be designated / / / -a-tocopherol to... 

Fig. 9.5 Chemical structures of low molecular weight antioxidants Melatonin (a) ascorbic acid (Vitamin C) (b) glutathione (c) lipoic acid (d) a-tocopherol (Vitamin E) (e) and a-tocotrienol (f)...

Ammonium Hydroxide DL-a-Tocopherol D-a-Tocopherol Concentrate Tocopherols Concentrate, Mixed D-a-Tocopheryl Acetate DL-a-Tocopheryl Acetate D-a-Tocopheryl Acetate Concentrate D-a-Tocopheryl Acid Succinate... 

More direct evidence for a role of lipid peroxidation in the development of post-traumatic spinal-cord ischemia is obtained from studies that have examined the effect of intensive antioxidant dosing on the progressive decline in SCBF after contusion injury in cats [28,29]. In one experiment, cats were pretreated daily with high oral doses of D-a-tocopherol (1000IU) and selenium (50 pg) for 5 days prior to spinal contusion injury. In untreated cats, moderately severe spinal contusion injury resulted in a progressive decrease in SCBF from near-normal levels immediately after injury to 53.5% below the pre-injury level 4 hours later. 

Based on biological assay in vitamin E-deficient rats, the vitamers have widely varying biological activity. The original international unit (iu) of vitamin E potency was equated with the activity of 1 mg of (synthetic) dl- -tocopherol acetate on this basis, pure D-a-tocopherol (i i i -a-tocopherol, the most potent vitamer) is 1.49 iu per mg. The precise mixture of stereoisomers in this original standard is unknown, and the different stereoisomers have very different biological activities, so that different preparations may differ considerably. 

It is now usual to express the vitamin E content of foods in terms of milligram-equivalents of (i i i )-a-tocopherol, based on their biological activities. In Table 4.1, the biological activity is shown in iuper milligram and relative to D-a-tocopherol on a molar basis. For the major vitamers present in foods, total a-tocopherol equivalent is calculated as the sum of mg a-tocopherol -I-... 

D-a-Tocopherol has also been used as a non-ionic surfactant in oral and injectable formulations. ... 

Synonyms natural alpha tocopherol (-l-)-(2R,4 R,8 R)-2,5,7,8-tetramethyl-2-(4, 8, 12 -trimethyltridecyl)-6-chro-manol d-a-tocopherol vitamin E. 

Synonyms ( )-a-tocopherol hydrogen succinate dl-a-toco-pheryl acid succinate d/-a-tocopherol succinate vitamin E. Appearance a practically odorless, white crystalline powder. Solubility practically insoluble in water slightly soluble in alkaline solutions soluble in acetone, ethanol (95%), ether, and vegetable oils very soluble in chloroform. 

Various mixtures of tocopherols, and mixtures of tocopherols with other excipients, are commercially available and individual manufacturers should be consulted for specific information on their products. The EINECS number for a-tocopherol is 215-798-8. The EINECs number for d-a.-tocopherol is 200-412-2 and the EINECS number for dl-a-tocopherol is 233-466-0. 

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