P-Tocotrienol

Fig. 1. The four naturally occutting tocopherols (a-tocopherol, E.E.E. [59-02-9] jall-rac [2074-53-5] (1) p-tocopherol [148-03-8] (2) y-tocopherol [54-28-4] (3) 8-tocopherol [119-13-1] (4)), a-tocotrienol [1721 -51 -3] (5), and p-tocotrienol [14101-61-2] (6) where asterisks denote asymmetric centers and the...

P-parinaric acid, physical properties, 5 33t P-pentenoic acid, physical properties, 5 3 It P-peroxylactones, 18 484 Beta phase titanium, 24 838 in alloys, 24 854-856 properties of, 24 840, 941 P-phellandrene, 24 493 P-picoline, 21 110 from acrolein, 1 276 uses for, 21 120 P-pinene, 3 230 24 496-497 major products from, 24 478 /-menthol from, 24 522 as natural precursor for aroma chemicals, 3 232 terpenoids from, 24 478-479 P-propiolactone, polymerization of, 14 259 P-quartz solid solution, 12 637—638 Beta ratio, in filtration, 11 329—330 Beta (P) rays, 21 285 P-scission reactions, 14 280-281 P-skytanthine, 2 101 P-spodumene solid solution, 12 638-639 P-sulfur trioxide, 23 756 P-sultones, 23 527 P-tocopherol, 25 793 P-tocotrienol, 25 793 P-vinylacrylic acid, physical properties, 5 33t... 

Barley grains contain all eight tocopherols and tocotrienols (Table 1.3), but there is a large variation in the total contents of tocopherols and tocotrienols. The major vitamers are a-tocotrienol (contributing to >50%), a-tocopherol, P-tocotrienol and y-tocotrienol, and they are generally correlated positively with each other (Peterson and Qureshi, 1993). The total vitamer content in whole-grain barley of 30 genotypes... 

Refined palm oil contains approximately 500 to 700ppm vitamin E, which is present as the RRR-a-tocopherol (30%) and tocotrienol (70%) isomers. In contrast, oils such as com, soybean, and sunflower are good sources of the tocopherols but contain no tocotrienols. Historically, vitamin E activity (one international unit, lU) has been defined as 1 mg of all rac-a-tocopheiyl acetate, whereas Img of all RRR-a-tocopherol equals 1.49 lU. In addition, vitamin E activity in foods is expressed as the a-tocopherol equivalent (a-TE), which is the activity of 1 mg of RRR-a-tocopherol. On this basis, conversion factors for each milligram of the different tocopherols and tocotrienols present in palm oil to a-TE have been calculated as follows a-tocopherol, 1.0 y-tocopherol, 0.5 5-tocopherol, 0.1 a-tocotrienol, 0.3 and P-tocotrienol, 0.05. The factors for y- and 5-tocotrienol are presently unknown." The conversion factors are based on the ability of each isomer to overcome specific vitamin E deficiency symptoms such as fetal resorption, muscular dystrophy, and encephalomalacia. Since these factors are based on rat fetal resorption assays, their relevance to humans... 

Nesaretnam, K., Stephen, R., Dils, R., and Darbre, P., Tocotrienols inhibit the growth of human breast cancer cells irrespectively of estrogen receptor status. Lipids, 33,461 69,1998. 

Fig. 3.46. Tocopherol and tocotrienol analysis by HPLC (according to Cavins and Inglett, 1974). 1 a-Tocopherol, 2 a-tocotrienol, 3 p-tocopherol, 4 y-tocopherol, 5 p-tocotrienol, 6 y-tocotrienol, 7 5-tocopherol, and 8 5-tocotrienol...

As a measure of their biological activity, all E vitamers can be assigned a potency, determined in a bioassay. One international unit (lU) is defined as the activity of 1 mg of flZZ-rac-a-tocopheryl acetate. Accordingly, the biopotencies of RRR-a-tocopheryl acetate, RRR-a-tocopherol and a/Z-rac-a-tocopherol have been calculated to be 1.36, 1.49, and 1.10 lU, respectively. The chirality of the C-2 atom is crucial to the activity, the 2-epimers having only one-third of the potency of the 2R forms. Biopotencies of tocopherols and tocotrienols can be expressed relative to that of a-tocopherol. Reported values (in %) are 100 (a-tocopherol), 40 (p-tocopherol), 8 (y-tocopherol), 1 (8-tocopherol), 21 (a-tocotrie-nol), and 4 (p-tocotrienol). This order parallels that of the relative antioxidant activity of the various vitamers (see B). 

NP chromatography [87,116] completely resolves the eight homologues, which elute in order of increasing polarity a-tocopherol, a-tocotrienol, p-tocopherol, y-tocopherol, p-tocotrienol, y-tocotrienol, 8-tocopherol, and 5-tocotrienol. The decreasing number of methyl groups and the unsaturation in the side chain make these compoimds more polar and therefore... 

Figure 1. The chemical structures of tocopherols and tocotrienols. For a-tocopherol and a-tocotrienol, R1=R2=R3=CH3 for P-tocopherol and P-tocotrienol, R1=R3=CH3, R2=H for y-tocopherol and y-tocotrienol, R1=H, R2=R3=CH3 for 8-tocopherol and S-tocotrienol, R1=R2=H, R3=CH3.

The modification of plasma lipid profiles by rice bran oil has been extensively studied and is the major health benefit highlighted in this section. Other health benefits associated with components of rice bran oil include suppression of B16 melanoma cell proliferation by y- and P-tocotrienols (He et al., 1997 Qureshi et al, 1997, 2000 Lane et al, 1999) and inhibition of tumor-promoting activity by oryzanols (Yasukawa et al, 1998 Akihisa et al, 2000). Cicero and Gaddi (2001) have reviewed other health benefits, including modulation of pituitary secretion and anti-ulcerogenic activity. 

The tocol derivatives (tocopherols and tocotrienols) are responsible for the vitamin E activity of plant tissues. Cereals can contain up to eight different tocol derivatives being the P-tocopherols and P-tocotrienols, which are most abundant in wheat, rye, and triticale. Conversely, the y-tocol derivatives are present in maize, rice, and millets. Barley contains both P- and y-tocol derivatives. Tocol derivatives are mainly located in the germ, and therefore migrate with the crude oil after mechanical or solvent extraction. 

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