Tocopherols vitamin tocotrienol

Vitamin E was first described ia 1922 and the name was originally applied to a material found ia vegetable oils. This material was found to be essential for fertility ia tats. It was not until the early 1980s that symptoms of vitamin E deficiency ia humans were recognized. Early work on the natural distribution, isolation, and identification can be attributed to Evans, Butt, and Emerson (University of California) and MattiU and Olcott (University of Iowa). Subsequentiy a group of substances (Eig. 1), which fall iato either the family of tocopherols or tocotrienols, were found to act like vitamin E (1 4). The stmcture of a-tocopherol was determined by degradation studies ia 1938 (5). 

Tocopherols and tocotrienols belong to the vitamin E family of compounds, which are potent antioxidants. The four isomers of tocotrienols (a-T3, P-T3, y-T3, 8-T3) are structurally related to their corresponding homologues of tocopherols (a-T, p-T, y-T, 8-T), but differ in their side-chain in that T3... 

The main problem in the vitamin E analysis is that it is easily oxidized, thereby an antioxidant, such as butyl hydroxy toluene (BHT) or ascorbic acid, is added to prevent degradation during the extraction step. The traditional method for extraction of tocopherols and tocotrienols in foods is solvent extraction (like soxhlet) and saponification with KOH [457,458]. Some authors have recently proved that saponification is not necessary [459-462], nevertheless, it has been widely applied until the present day. 

Determination of vitamin E isomers in seeds and nuts Determination of tocopherol and tocotrienol in rice bran Investigation of vitamin E content in olives Determination of tocopherol and tocotrienol in olive oils... 

Vitamin E is a collective term for all of the tocopherols and tocotrienols. Of these, one of the most active is (-)-o-tocopherol 6. Lutz Tietze of the Universitiit Gottingen has reported (Angew. Chem. bit. Ed. 2005,44,257) that the Pd-catalyzed cascade cyclization of 4 to 5 proceeds with 96% . 

Tobacco mosaic virus 247, 334s, 336s Tocopherols 392,815 — 822,818 as antioxidants 822 a-Tocopherol (vitamin E) 819s Tocopherolquinone 818, 819, 819s Tocotrienols 818 Togavirus 247... 

Currently, high-performance liquid chromatography (HPLC) methods have been widely used in the analysis of tocopherols and tocotrienols in food and nutrition areas. Each form of tocopherol and tocotrienol can be separated and quantified individually using HPLC with either a UV or fluorescence detector. The interferences are largely reduced after separation by HPLC. Therefore, the sensitivity and specificity of HPLC methods are much higher than those obtained with the colorimetric, polarimetric, and GC methods. Also, sample preparation in the HPLC methods is simpler and more efficiently duplicated than in the older methods. Many HPLC methods for the quantification of tocopherols and tocotrienols in various foods and biological samples have been reported. Method number 992.03 of the AOAC International Official Methods of Analysis provides an HPLC method to determine vitamin E in milk-based infant formula. It could probably be said that HPLC methods have become dominant in the analysis of tocopherols and tocotrienols. Therefore, the analytical protocols for tocopherols and tocotrienols in this unit are focused on HPLC methods. Normal and reversed-phase HPLC methods are discussed in the separation and quantification of tocopherols and tocotrienols (see Basic Protocol). Sample... 

Research Council defined 1 mg of a-tocopherol as 1 unit of a-TE (mg x 1). The activities as a-TE of other vitamers were (3-tocopherol, mg x 0.5 y-tocopherol, mg xO. 1 8-tocopherol, mg x 0.03 a-tocotrienol, mg x 0.3 and (3-to-cotrienol, mg x 0.05. The activities of y- and 8-tocotrienol were undetectable. The Recommended Dietary Allowances (RDAs) are only based on intake of the 2R-stereoisomeric forms of a-tocopherol (RRR-, RSR-, RRS-, and RSS-tocopherol) from food, fortified food, and vitamin supplements (Food and Nutrition Board, 2000). The 2S-stereoisomeric forms of a-tocopherol and the other tocopherols ((3-, y-, and 5-tocopherol) and tocotrienols are not used to estimate the RDAs. 

Vitamin E is a generic term that represents four tocopherols and four tocotrienols of varying biological potency. The term tocopherol correctly refers to the methyl-substituted derivatives of to-col and is not synonymous with the term vitamin E. The tocopherols and tocotrienols may be referred to collectively as tocochromanols. Many of the diverse deficiency syndromes observed in animals experimentally deprived of vitamin E can be explained by the vitamin s acting as an antioxidant in stabilizing unsaturated lipids in biological membranes. 

It is fortuitous that indigenous concentrations of vitamin E in the principal food sources are on the order of mg rather than yug/100 g, for the tocopherols and tocotrienols exhibit relatively low intensities of UV absorption. Individual vitamers are characterized by a slightly different absorption maximum within the wavelength range of 292-298 nm in ethanol. Published A] m values for the tocopherols at their Amax in ethanol are a-T 70-73.7 at 292 nm, (3-T 86-87 at 297 nm, y-T 90-93 at 298 nm, and <5-T 91.2 at 298 nm (126). The different absorption characteristics among the vitamers necessitates the running of individual standards for accurate quantitation of each vitamer. The absorption intensity of a-tocopheryl acetate is lower still with an A j m value of only 40-44 at the Amax of 285.5 nm (44). Reported minimum detectable quantities of a-, / -, y-, and (5-tocopherols at 295 nm are, respectively, 50 ng, 70 ng, 90 ng, and 130 ng (127). 

Retinol and its esters and unesterified tocopherols and tocotrienols possess strong native fluorescence, but neither vitamin D nor vitamin K fluoresce. The carotenoids commonly associated with foods do not fluoresce to any significant extent, except notably phytofluene, which is found in considerable amounts in tomatoes (22) and in smaller amounts in carrots (130) and which fluoresces six times more intensely than retinyl acetate (131). 

Indyk and Woollard (195) demonstrated that the removal of cholesterol from the un-saponifiable fraction of vitamin D-supplemented whole milk powder by methanolic precipitation and filtration was an adequate cleanup procedure, making semipreparative HPLC unnecessary. This simplified procedure was made possible by connecting two analytical columns in series. The tandem columns adequately separated vitamins D2 and D3 from one another and from vitamins A and E. The analysis of infant formulas (100) required cleanup by silica solid-phase extraction to remove the minor tocopherols and tocotrienols, which constituted potential sources of interference. 

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)...

Tocopherols and tocotrienols are precursors of vitamin E and are important antioxidants in oils. Their reactivity means that they are not stable to many oil processing procedures, including deodorization, which reduces levels by up to 15%. Levels of tocopherols in cocoa butter are usually about 100-300 mg/kg, with the y-isomer (IV) being the major component (about 90%), but they can be entirely absent (Lipp et al., 2001) (Figure 3.3). Tocotrienols have a similar structure with unsaturation of alternate bonds along the alkyl chain. Only y-tocotrienol is found in cocoa butter and this at low levels (< 5 mg/kg). Palm oil is notably high in tocopherols and tocotrienols, of which a-tocopherol and a-tocotrienol make up 20% to 30% each with most of the remainder as y-tocotrienol. 

Tocopherols and tocotrienols are considered to be lipids. Lipids are a broad group of natural hydrophobic compounds which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglyceiides, diglycerides, phospholipids, and others. In recent years the scientific disciplines of genomics and proteomics were developed to attempt to provide systems to quantitatively catalog all of the DNA and protein sequences, respectively, for species and tissues. 

Tocopherols and tocotrienols are often discussed as compounds with separate biological, vitamin, and antioxidant functions, although in a comprehensive review of Traber and Atkinson (2007) it was concluded that all of the biological activities of tocopherols and tocotrienols can be understood and derived from their antioxidant activity to protect polyunsaturated lipids from oxidation in membranes. 

Until the year 2000, all tocopherols and tocotrienols were considered to have the same biological activity of a-tocopherol, i.e. vitamin E activity. a-Tocopherol was considered to have the highest activity followed by 3- and y-tocopherol with 50% and 10% of the activity of a-tocopherol. Nutrition data was often reported in a-tocopherol equivalents (a-TE) that were expressed as follows (McLaughlin and Weihrauch, 1979 Schakel et al., 1997) amounts of a-TE were calculated as mg of a-tocopherol, 0.5 x mg of 3-tocopherol, 0.1 x mg... 

Several reversed-phase HPLC methods have also been reported for the quantitative analysis of tocopherols and tocotrienols (Table 11.6). To be able to separate all eight tocols a pentafluorophenylsilica column (Abidi, 2003) was used. A C30-bonded phase silica column separated the three tocotrienols, a-tocopherol, and a-tocomonoenol in palm oil (Ng et al., 2004). C30-bonded silica columns have also been used to simultaneously analyze tocopherols, other fat-soluble vitamins, and carotenoids (Gentili and Caretti, 2011). 

Numerous mass spectra of tocopherols and tocotrienols have been published and many are available in the NIST/EPA/NIH Mass Spectral Library (2011) and MassBank (2011). In addition to the above chromatographic and nonchromatographic methods for tocol analysis, kits are also commercially available for the ELISA (Enzyme-linked im-munoabsorbent assay) of vitamin E. 

Hunter, S.C. Cahoon, E.B. 2007. Enhancing vitamin E in oilseeds Unraveling tocopherol and tocotrienol biosynthesis. Lipids. 42 97-108. 

Muller, L. Theile, K. Bohm, V. 2010. In vitro antioxidant activity of tocopherols and tocotrienols and comparison of vitamin E concentration and lipophilic antioxidant capacity in human plasma. Mol. Nutr. Food Res. 54 731-742. 

Normal-Phase Chromatography Example. Vitamin E, an antioxidant, is a complex made up of tocopherols and tocotrienols (Figure 8-62), which are sometimes used to stabilize formulations. Tocopherols are a series of related benzopyranols with a C16 saturated side chain. Tocotrienols contain three double bonds on the C16 side chain [32]. 

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