D-y-Tocopherol

In order to prepare C -labeled d-a-tocopherol we started from natural d-7-tocopherol (Fig. 6) and introduced the C -methyl group into the 5-position by use of the Mannich reaction. Condensation of d-y-tocopherol with radioactive paraformaldehyde in the presence of diethylamine followed by catalytic reduction gave d-a-tocopherol. This was acetylated to methyl-C Mabeled d-a-tocopherol acetate (specific activity 1.7 tc/mg Fig. 6). 

Synonyms 3,4-Dihydro-2,7,8-trimethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-ol D-y-Tocopherol RRR-y-Tocopherol 7,8-Trimethyltocol 2,7,8-Trimethyl-2-(4,8,12-trimethyltridecyl)-6-chromanol... 

In reversed-phase HPLC on a Cl8 column, only six peaks are usually found, and their order of elution is 5-tocotrienol, (3- and y-to-cotrienols, a-tocotrienol, 5-tocopherol, (3- and y-tocopherol, and a-tocopherol. Figure D 1.5.4 is an example of a reversed-phase chromatograph of tocopherols and tocotrienols in rice bran oil. The tocols with unsaturated side chain have shorter retention time than those with saturated side chain. The methyl substituents on the chromanol ring also affect the retention times of tocopherols and tocotrienols. However, the effect is reversed, compared with the normal-phase HPLC method. 

Milatovic D., VanRollins M., Li K., Montine K. S., and Montine T. J. (2005). Suppression of murine cerebral F2-isoprostanes and F4- neuropiostanes from excitotoxicity and innate immune response in vivo by a- or y-tocopherol. J. Chromatogr. B-Anal. Technol. Biomed. Life Sci. 827 88-93. 

Figure 8.6 Influence of time constant on peak shape and sensitivity (A) 0.2 sec (B) 2 sec. Column, 50 mm X 4.6 mm I.D. C]g (3 /am). Peaks 1, cr-tocopherol 2, /3-tocopherol 3, -y-tocopherol 4, 5-tocopherol. (Adapted from Ref. 1 with permission.)...

The high-alpha type contains a relatively high proportion of RRR-a-tocopherol and is recognized as a form of vitamin E and also as an antioxidant. The low-alpha type contains a relatively high proportion of d-(3-, D-y-, and D-S-tocopherols, with a minor level of RRR-a-tocopherol, and thus is not considered to be a form of vitamin E, but rather an antioxidant. Both types may contain an edible vegetable oil added to adjust... 

Labeling High-Alpha Type Indicate the milligrams per gram of total tocopherols and of RRR-a-tocopherol present. All label claims that are in terms of International Units (IU) should be based on the following 1 mg of RRR-a-tocoph-erol = 1.49 IU. Low-Alpha Type Indicate the milligrams per gram of total tocopherols and of d-(3- plus D-y- plus d-8-tocopherols present. 

Assay High-Alpha Type Not less than 50.0% of total tocopherols, of which not less than 50.0% consists of RRR-a-tocopherol (C29H50O2) and not less than 20.0% consists of d-3- plus D-y- (C28H48O2) plus D-S-tocopherols (C27H46O2). Low-Alpha Type Not less than 50.0% of total tocopherols, of which not less than 80.0% consists of d-(3- plus D-y- plus D-S-tocopherols. 

Fuster, M.D., Lampi, A.-M., Hopia, A., and Kamal-Eldin, A. 1998. Effects of a- and y-Tocopherols on the Autoxidation of Purified Sunflower Triacylglycerols. Lipids. 33 715-722. 

Borage leaf and whole herb can be purchased by the ounce. Borage seed oil softgel, 1000 mg (240 mg of y-linolenic acid plus linoleic acid and 10 IU of vitamin E [d-a-tocopherol]), 1300-mg borage oil capsules (300 mg of y-linolenic acid, 494 mg of linoleic acid, 221 mg of oleic acid), borage oil hard gelatin capsules (67 mg of y-linolenic acid and 170 mg of linoleic acid), and 500-mg borage oil capsules are available. The oil is also available in bulk. 

Saldeen, T., Li, D.Y. and Mehta, J.L. (1999) Differential effects of alpha and gamma-tocopherol on low-density lipoprotein oxidation, superoxide activity, platelet aggregation and arterial thrombogenesis. J. Am. Coll. Cardiol., 34, 1208—1215. 

Khor, H.T. and Chieng, D.Y., Effect of dietary supplementation of tocotrienols and tocopherols on serum lipids in the hamster, Nutr. Res., 16,1393-1401, 1996. 

DL-a Tocopherol. See Tocopherol (R,R,R)-a-Tocopherol. See,D-a-Tocopherol RRR-y-Tocopherol. See (+)-y-Tocopherol d,l-a-Tocopherol acetate ( )-o-Tocopherol acetate. See dl-a-Tocopheryl acetate a-Tocopherol acid succinate. See Tocopheryl succinate... 

The tocopherol content of a castor oil as determined by TLC, (thin-layer chromatography) was a-tocopherol (28 mg/kg), jS-tocopherol (29 mg/kg), y-tocopherol (111 mg/kg), and d-tocopherol (310mg/ kg). A range of 400-500mg/kg total tocopherol has been reported (Muller-Mulot, 1976). 

Estimation of true vitamin E in foods requires quantitative determination of all its components since they vary in their biological potency. This vitamin consists of four tocopherols (a, jS, y, and 6) and four tocotrienols (a, jS, y, and d), but the three major constituents responsible for vitamin E activity are the a-, jS-, and y-tocopherols. While these compounds are fluorescent, their esters must be reduced to free alcohols for total tocopherol assays. Total vitamin E can be directly obtained through fluorimetry, but the determination of individual components is carried out using LC with fluorimetric detection. This procedure has been used to determine the composition of vitamin E in seed oils from maize, olives, soya beans, sesame, safflower, and sunflower by measuring the content of all the four tocopherols plus a-tocotrienol. The simultaneous determination of tocopherols, carotenes, and retinol in cheese has been carried out using LC with two programmable detectors coimected in series, a spectrophotometer and a fluorimeter. Carotenes have been determined photometrically, and fluorimetric measurements have been obtained for tocopherol and retinol. 

Figure 1. HPLC-ELSD chromatogram of corn fiber oil. Insert shows the structure of sitostanyl-ferulate, the major ferulate-phytosterol ester in corn fiber oil (Norton, 1995). Abbreviations StE, phytosterol fatty acyl ester TAG, triacylglycerol, a-Toc, a-tocopherol FFA, free fatty acids CE, p-coumarate-phytosterol esters y-Toc, y tocopherol ST, free phytosterols 1,3-D, 1,2-diacylglycerols FE, ferulate-phytosterol esters 1,2-D, 1,2-diacylglycerols.

Propyl gallate (PG) increases the efficiency of BHA, but not that of BHT. Ascorbyl palmitate, which is by itself a rather weak antioxidant, substantially sustains the antioxidative activity of y,d,l-tocopherol. 

Vitamin E Status of Humans. As hypovitaminosis E is a rare event (see D), a routine assessment of the vitamin E status in humans is not required but only justified for risk groups (e.g., prematures) and as part of studies on the chemoprevention of diseases presumably involving oxidative stress as an etiological factor, e.g., cancer, atherosclerosis, and cataract. Knowledge about the in vivo fate of vitamin E (see C) will guide in the choice of samples to be analyzed. The most common, easily obtainable biological matrix for the determination of vitamin E and of a-tocopherol in particular is plasma/serum. Plasma levels of Y-tocopherol, which is more abundant in foods, are of little importance except... 

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