Grains Tocotrienols

Oats Oat grain and oat oil contain both tocopherols and tocotrienols. The major tocols are a-tocopherol and a-tocotrienol. Significant variations occur in tocol composition of oat oil due to the oat variety and milling process used for the study. Total tocol content of oat oil varies from 175 ppm to 640 ppm (125). a-Tocopherol (20-82% of the total tocols), a-tocotrienol (16-51% of total tocols), 5-tocotrienols (0-12% of total tocols), and y-tocopherol (0-36% of total tocols) are the predominant tocol isomers reported in the oat oil. 

Wheat grains contain total tocopherol and tocotrienol of >40 pg/g (e.g., Barnes, 1983 White and Xing, 1997), where p-tocotricnol (>50%) and a-tocopherol... 

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... 

Tocopherol and tocotrienol profiles of buckwheat and millet are different compared to other cereal grains. In both cereals, y-tocopherol is the dominant vitamer, and tocotrienols occur in minor amounts. Buckwheat contains 54-62 pg/g and millet 22-32 pg/g of vitamers, of which ca 90% and 70% is y-tocopherol (Piironen et al., 1986 Balz et al., 1992). Grain amaranth of several cultivars and growing environments showed a large variation in the content of total E-vitamers, 5-29 pg/g, and tocotrienols, mainly 3- and y-, representing 39-74% of this total (Lehmann et al., 1994). 

STABILITY OF TOCOPHEROLS AND TOCOTRIENOLS DURING PROCESSING AND STORAGE OF OIL AND CEREAL GRAINS AND THEIR PRODUCTS... 

Any processing of grains subjects tocopherols and tocotrienols to oxidation. When linseeds and rapeseeds to be used for poultry feeding were crushed and stored either at room temperature or in a cold room, a 50% reduction in the tocopherol content occurred in 30 days (Gopalakrishnan et al., 1996). 

Plants appear to have certain quaUtative and quantitative strategies for designing their PUFA/tocopherol mixtures (1) y-tocopherol appears to be the main antioxidant for the depot lipids of oilseeds and nuts, especially those rich in hnolenic acid (2) both a-and p-tocopherols and tocotrienols are important for the protection of PUFA of cereal grains and (3) lipids in the green parts of plants are usually protected by low amounts of a-tocopherol synergized by other phenohc and non-phenolic antioxidants (Kamal-Eldin, 1999). The thermal stabihty of tocopherols increases in the following order a-tocopherol < p-tocopherol < y-tocopherol 5-tocopherol (Yoshida and Tagaki, 1999). 

Tocotrienols Grains, palm oil Inhibit breast cancer cell growth, possess cholesterol-lowering property... 

Tocopherols and tocotrienols are abundant in seeds, grains, and vegetable oils (46), but only the tocopherols are absorbed by humans to an appreciable extent (47). a-Tocopherol is the predominant form in plasma and is biologically the most active homolog. Although its exact biochemical function in humans is controversial, vitamin E is known to protect membrane lipids from peroxidation by scavenging free radicals and other oxidative species (48). A number of oxidized metabolites, e.g. a-tocopherylquinone have been suggested (49). 

Colombo, M.L., Marangon, K. and Bugatti, C. (2009) CoulArray electrochemical evaluation of tocopherol and tocotrienol isomers in barley, oat and spelt grains. Nat. Prod. Commun., 4,251-254. 

Tocopherols and tocotrienols are biosynthesized only by plants. In leaves, a-tocopherol is found mainly in the chloroplasts, whereas the y- and 8-forms are extraplastidic. Seeds and grains also contain a-tocopherol but are often more abundant in y-tocopherol. The richest sources of vitamin E are plant oils such as sunflower and wheat germ oil. Tocotrienols do not occur in green tissues but rather in the bran and germ of plants. 

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