Tocotrienols, structure

AOCS Lipid Library. 2011. Tocopherols and tocotrienols Structure, composition, biology and analysis, from www.lipidlibrary.aocs.org, accessed April 2011. 

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... 

Figure 15.14 Structural formula of a-tocopherol. In P-tocoph-erol, the 7-methyl group is absent, in y-tocopherol the 5-methyl group is absent, and in 5-tocopherol, both methyl groups are absent. In the tocotrienols, the side-chain at position 2 is replaced by ...

In normal-phase HPLC on a silica column, separation is based on the number and position of methyl substituents on the chromanol ring. In reversed-phase HPLC on a Cl8 column, separation is based on the structure of the side chain and the number of methyl substituents. It is therefore difficult to completely separate [3-and y-tocopherol and (3- and y-tocotrienols by reversed-phase HPLC, because both have the same side-chain structure and number of methyl substituents on the chromanol ring. Only six peaks are usually found in the reversed-phase HPLC method. Thus, reversed-phase HPLC is recommended for samples from animal tissues, which contain little or no P and y vitamers. 

Tocopherols and tocotrienols AOAC methods, 479-480 (tables) biological activity, calculation of, 489 characteristics and structure of, 485-486 HPLC, 480-481,486-487, 489 sample preparation, 481 -485, 487-489 Tocotrienols. see Tocopherols and tocotrienols... 

Tocopherols comprise a methyl-substituted chroman-6-ol ring attached at C-2 to a saturated iso-prenoid side chain. Tocotrienols are analogous structures whose side chains contain three trans double bonds. The tocopherols and tocotrienols are designated as a, (S, y, and 8, according to the number and position of the methyl substituents in the chromanol ring (Fig. 5). 

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 sometimes referred to as tocochro-manols, or simply abbreviated to tocols. The structures of the four... 

Recent developments in the area of oils and fats has led to the production of specialty lipids from novel sources such as fruit seeds, nuts, and other minor plant sources. In addition, preparation of structured lipids for a myriad of applications has been of interest. Minor components of oils and fats may be isolated during processing and used as nutraceutical and functional food ingredients. Examples are lecithin, phytosterols, tocopherols, and tocotrienols, among others. Obviously, the health-promoting potential of such products is also of interest. 

Tocopherols and tocotrienols, collectively known as tocols, are monophenolic and lipophilic compounds that are widely distributed in plant tissues (7). The main commercial source of natural tocopherols is the soybean oil. Tocotrienols, less common than tocopherols, are present in palm oil, rice bran oil, as well as cereals and legumes (11). Tocopherols and tocotrienols are classified into a-, (3-, y-, and 5-, depending on their chemical structures (Figure 7). In general, tocotrienols have a stronger antioxidant effect on lipid oxidation than tocopherols. The antioxidant activity of tocopherols is dependent on temperature and is in the order of 5- > y->P-> oc-tocopherol (7). Tocopherols (mixed natural concentrate) are a golden... 

The tocopherols and tocotrienols are generally not the major components of vegetable oil, but their presence is vital for stabilizing the unsaturated fatty acids of these oils against oxidative deterioration (39). Their structures are based on a chroman head with two rings, one phenolic and one heterocyclic, and a phytyl tails isoprenoid side chain at C-2. The phytyl tail is saturated in the case of... 

TABLE 6. Structures, Trivial, and lUPAC Numbers of Tocopherols, Tocotrienols, and Related Compounds Present in Vegetable Oils. 

The term vitamin E refers to two groups of compounds, the tocophenols and the tocotrienols. The structures of these compounds appear in Figure 9.90. All forms of the vitamin contain two parts, a "head" and a "tail." The head consists of an aromatic ring structure, called chroman or chromanol, and is the site of antioxidant action. The tail of tocopherols is a phytyl group, while the tail of tocotrienols is a polyisoprenoid group. The tail of vitamin K setv es to anchor the vitamin in lipid membranes, in the lipids of adipose tissue, and in the lipid surface and core of the lipoproteins. 

Structures of naturally occurring plant compounds having vitamin E activity. The nucleus in each is 6-hydroxychroman. Attachment of a saturated 16-carbon chain produces the tocopherols the tocotrienols have a 16-carbon unsaturated chain. Both groups are optically active. The tocotrienols have one chiral center at carbon 2, while the tocopherols have three, at carbons 2,4, and 8. Tocol is a tocopherol in which R i, R2, and R3 are all hydrogen atoms. The tocopherols can be viewed as methylated tocols. 

Fig-1 Structures of natural phytol, vitamin l[Pg.72]

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