Tocopherols alpha

Alpha-tocopherol (AL-fa toe-KOF-er-ol) is also known as 2,5,7,8-tetramethyl-2-(4,8,i2-trimethyltridecyl)chroman- 

Vitamin E was discovered in 1922 by two scientists at the University of California at Berkeley, Herbert McLean Evans 

Alpha tocopheryl. Red atoms are oxygen white atoms are hydrogen and black atoms are carbon. PUBLISHERS RESOURCE GROUP 

Vitamin E was first produced synthetically (artificially) in 1938 by Swiss chemist Paul Karrer (1889-1971), who had been awarded the Nobel Prize in chemistry a year earlier for his studies of vitamin A, vitamin B2, and other important biological compounds. 

A variety of methods is now available for the synthesis (artificial production) of the tocopherols. In the most commonly used procedure, 2,3,5-trimethylhydroquinone is reacted with isophytol over one of many possible catalysts. A small amount of the vitamin is still obtained from natural sources, usually as the by-product in the treatment of one of its natural sources. 

Note that alpha tocopherol has three chiral centers, giving rise to eight isomeric forms. The naturally occurring form is known as d-alpha tocopherol or (2R,4 R,8 R)-alpha-toco-pherol. The synthetic form, d/-alpha tocopherol or simply alpha tocopherol, occurs as a racemic mixture containing equimolar quantities of all the isomers. 

Similar considerations apply to beta, delta, and gamma tocopherol and tocopherol esters. 

Alpha tocopherol is primarily recognized as a source of vitamin E, and the commercially available materials and specifications reflect this purpose. While alpha tocopherol also exhibits 

Alpha-tocopherol is a highly lipophilic compound, and is an excellent solvent for many poorly soluble drugs.Of widespread regulatory acceptability, tocopherols are of value in oil- or fat-based pharmaceutical products and are normally used in the concentration range 0.001-0.05% v/v. There is frequently an optimum concentration thus the autoxidation of linoleic acid and methyl linolenate is reduced at low concentrations of alpha tocopherol, and is accelerated by higher concentrations. Antioxidant effectiveness can be increased by the addition of oil-soluble synergists such as lecithin and ascorbyl palmitate.  

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

---

Alpha-Step MC48 Alpha techno DL-alpha tocopherol Alphavims Alphenate Alphol... 

Examine the geometry of the most stable radical. Is the bonding in the aromatic ring fuUy delocalized (compare to model alpha-tocopherol), or is it localized Also, examine the spin density surface of the most stable radical. Is the unpaired electron localized on the carbon (oxygen) where bond cleavage occurred, or is it delocalized Draw all of the resonance contributors necessary for a full description of the radical s geometry and electronic structure. 

The term vitamin E describes a family of eight antioxidants, four tocopherols, alpha (a), beta ((3), gamma (y) and delta (8), and four tocotrienols (also a, (3, y, and 8). a-Tocopherol is present in nature in only one form, RRR a-tocopherol. The chemical synthesis of a-tocopherol results in eight different forms (SRR, SSR, SRS, SSS, RSR, RRS, RSS, RRR), only one of which is RRR a-tocopherol. These forms differ in that they can be right (R) or left (S) at three different places in the a-tocopherol molecule. RRR a-tocopherol is the only form of vitamin E that is actively maintained in the human body and is therefore the form of vitamin E found in the largest quantities in the blood and tissue. A protein synthesized in the liver (a-TTP alpha-tocopherol transfer protein) preferentially selects the natural form of vitamin E (RRR a-tocopherol) for distribution to the tissues. However, the mechanisms for the regulation of vitamin E in tissues are not known... 

Sano M, Ernesto C, Thomas RG et al (1997) A controlled trial of selegiline, alpha-tocopherol, or both as treatment for Alzheimer s disease. The Alzheimer s Disease Cooperative Study. N Engl JMed 336 1216-1222... 

Antioxidants (magnesium,ascorbic acid, alpha-tocopherol)... 

Eberlein-Konig B, Placzek M, Pryzbilla B (1998) Protective effect against sunburn of combined systemic ascorbic acid (vitamin C) and d-alpha-tocopherol (vitamin E). J Am Acad Dermatol 38 45-48... 

ALBANES D, HEINONEN O P, HUTTUNEN J K, TAYLOR P R, VIRTAMA J, EDWARDS B K, HAAPAKDSKI J, RAUTALATHI M, HARTMAN A M and PALMGREN J (1995) Effects of alpha-tocopherol and beta carotene supplements on cancer incidence in the alpha-tocopherol beta-carotene cancer prevention study , Am J Clin Nutr, 62, 1427S-30S. 

ALPHA-TOCOPHEROL BETA-CAROTENE (ATBC) CANCER PREVENTION STUDY GROUP (1994) The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers , New Engl J Med, 330, 1029. 

It is well known that excessive intake of P-carotene may lead to carotenodermia (yellow skin), and it is undoubtedly the case that some carotenoid is directly lost via the skin or through photo-oxidation in the skin. As far as is known the carotenoids are not cytotoxic or genotoxic even at concentrations up to 10 times the normal plasma concentration which may cause carotenodermia. However, they are associated with amenorrhoea in girls who may be consuming bizarre diets and, in long-term supplementation studies, with an increase in lung cancer (The Alpha-tocopherol, Beta-carotene Cancer Prevention Study Group, 1994). 

ATBC = Alpha Tocopherol Beta Carotene Prevention Study CARET = The Beta Carotene and Retinol Efficacy Trial PHYS = Physicians Health Study. 

ALBANES D, HEiNONEN o p, TAYLOR p R, et uL, (1996) a-tocopherol and P-carotene supplementation and Irmg cancer incidence in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study effect of base-line chacteristics and study compliance. J Natl Cancer Inst. 88 1560-70. 

Nonaqueous Systems In nonaqueous (nonpolar) solvent systems, nitrosatlon also proceeds. In these solvents, alpha-tocopherol acts as a lipid soluble blocking agent in much the same fashion as ascorbic acid functions in the aqueous phase. Alpha-tocopherol reacts with a nitrosating agent and reduces it to nitric oxide. At the same time, alpha-tocopherol is oxidized to tocoquinone, which is the first oxidation product of vitamin E and also a normal metabolite in vivo. 

Aside from ascorbic acid and alpha-tocopherol, which have been shown to be effective blocking agents, there are other factors which appear important in blocking nitrosamine formation... 

Ascorbic acid and alpha-tocopherol are effective blocking agents against N-nitroso compound formation. Ascorbic acid is effective particularly in aqueous media, and tocopherol effective particularly in lipid phases. They should be used in conjunction due to the mutually complementary actions of the two vitamins in blocking nitrosamine formation in both aqueous and lipid media. 

Primary prevention trial (Alpha-Tocopherol, 20 mg/day, 5 to 8 yr P-Carotene Lung cancer -t 35... 

Dorgan, J.F. et al.. Relationships of serum carotenoids, retinol, alpha-tocopherol, and selenium with breast cancer risk results from a prospective study in Columbia, Missouri (United States), Cancer Causes Control, 9, 89, 1998. 

Holick, C.N. et al., Dietary carotenoids, serum beta-carotene, and retinol and risk of lung cancer in the alpha-tocopherol, beta-carotene cohort study, Am. J. Epidemiol., 156, 536, 2002. 

Albanes, D. et al., Effects of supplemental alpha-tocopherol and beta-carotene on colorectal cancer results from a controlled trial (Finland), Cancer Causes Control, 11, 197, 2000. 

Mafila, N. et al.. Dietary and serum alpha-tocopherol, beta-carotene and retinol, and risk for colorectal cancer in male smokers, Eur. J. Clin. Nutr, 56, 615, 2002. 

Street, D.A. et al.. Serum antioxidants and myocardial infarction are low levels of carotenoids and alpha-tocopherol risk factors for myocardial infarction Circulation, 90, 1154, 1994. 

Tomwall, M.E. et al.. Effect of alpha-tocopherol and beta-carotene supplementation on coronary heart disease during the 6-year post-trial follow-up in the ATBC study, Eur. Heart J, 25, 1171, 2004. 

Fukuzawa, K. et ah. Rate constants for quenching singlet oxygen and activities for inhibiting lipid peroxidation of carotenoids and alpha-tocopherol in liposomes. Lipids, 33, 751, 1998. 

The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study Group, New Engl. J. Med., 330, 1029, 1994. 

Takahashi, A., Shibasaki-Kitakawa, N., and Yonemoto, T., A rigorous kinetic model for beta-carotene oxidation in the presence of an antioxidant, alpha-tocopherol, J. Am. Oil Chem. Soc., 80, 1241, 2003. 

Pastori, M. et al., Lycopene in association with alpha-tocopherol inhibits at physiological concentrations proliferation of prostate carcinoma cells, Biochem. Biophys. Res. Com., 250, 582, 1998. 

Albanes, D. et al., Effect of supplemental P-carotene, cigarette smoking and alcohol consumption on serum carotenoids in alpha-tocopherol, P-carotene cancer prevention study, Am. J. Clin. Nutn, 66, 366, 1976. 

Scarpa, M., Rigo, A., Maiorino, M., Ursini, F. and Gregolis, C. (1984). Formation of a-tocopherol radical and recycling of alpha tocopherol by ascorbate during peroxidation of phosphatidylcholine liposomes. An electron paramagnetic resonance study. Biochim. Biophys. Acta 801, 215-219. 

Fukuzawa, K. Gebicki, J. M. Oxidation of alpha-tocopherol in micelles and liposomes by the hydroxyl, perhydroxyl, and superoxide free radicals. Arch. Biochem. Biophys. 1983, 226, 242-251. 

Omura, K. Iodine oxidation of alpha -tocopherol and its model compound in alkaline methanol unexpected isomerization of the product quinone monoketals. J. Org. Chem. 1989, 54, 1987-1990. 

The interaction of carotenoids with cigarette smoke has become a subject of interest since the results of the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study Group 1994 (ATBC) and CARET (Omenn et al. 1996) studies were released. P-Carotene has been hypothesized to promote lung carcinogenesis by acting as a prooxidant in the smoke-exposed lung. Thus, the autoxidation of P-carotene in the presence of cigarette smoke was studied in model systems (toluene) (Baker et al. 1999). The major product was identified as 4-nitro-P-carotene, but apocarotenals and P-carotene epoxides were also encountered. 

Balazs, Z, Panzenboeck, U, Hammer, A, Sovic, A, Quehenberger, O, Malle, E, and Sattler, W, 2004. Uptake and transport of high-density lipoprotein (HDL) and HDL-associated alpha-tocopherol by an in vitro blood-brain barrier model. J Neurochem 89, 939-950. 

Mardones, P and Rigotti, A, 2004. Cellular mechanisms of vitamin E uptake Relevance in alpha-tocopherol metabolism and potential implications for disease. J Nutr Biochem 15, 252-260. 

McClure, TD and Liebler, DC, 1995. Electron capture negative chemical ionization mass spectrometry and tandem mass-spectrometry analysis of beta-carotene, alpha-tocopherol and their oxidation products. J Mass Spectrom 30, 1480-1488. 

Reboul, E, Thap, S, Perrot, E, Amiot, MJ, Lairon, D, and Borel, P, 2007a. Effect of the main dietary antioxidants (carotenoids, gamma-tocopherol, polyphenols, and vitamin C) on alpha-tocopherol absorption. Eur J Clin Nutr 61, 1167-1173. 

Wrona, M, Rozanowska, M, and Sarna, T, 2004. Zeaxanthin in combination with ascorbic acid or alpha-tocopherol protects ARPE-19 cells against photosensitized peroxidation of lipids. Free Radic Biol Med 36, 1094-1101. 

---