Discovery of Tocotrienols
The discovery of tocotrienols was first reported by Pennock and Whittle (USDA, Liverpool) in 1964, describing the isolation of tocotrienols from rubber. The biological significance of tocotrienols was clearly delineated in the early 1980s, when its ability to lower cholesterol was first reported by Qureshi and Elson (UWisconsin/Madison). During the 1990s, the anti-cancer properties of tocopherols and tocotrienols began to be delineated.
The current commercial sources of tocotrienol are rice, palm, and annatto. The ratio of tocopherol-to-tocotrienol in rice, palm, and annatto is 50:50, 25:75, and 0.1:99.9, respectively. α-tocopherol makes up roughly 25–50% of palm and rice vitamin E mixtures, respectively, and has been shown to interfere with tocotrienol benefits. Annatto, on the other hand, naturally contains only δ- and γ-tocotrienols and is essentially tocopherol-free, hence not confined by α-tocopherol interference issues.
Other natural tocotrienol sources include rice bran oil, coconut oil, cocoa butter, barley, and wheat germ. Sunflower, peanut, walnut, sesame, and olive oils, however contain only tocopherols. Vitamin E supplements typically supply 50–200 mg/day of mixed tocotrienols. In a number of clinical trials, doses of tocotrienols as low as 42 mg/day have shown to reduce blood cholesterol levels by 5–35%. Tocotrienols are safe and human studies show no adverse effects with consumption of 240 mg/day for 48 months.
Tocotrienol rich fractions from rice, palm, or annatto, used in nutritional supplements, functional foods, and anti-aging cosmetics, are available in the market at 20%, 35%, 50%, and 70% total vitamin E content. Molecular distillation occurs at lower temperatures and reduces the problem of thermal decomposition. High vacuum also eliminates oxidation that might occur in the presence of air. For the utility and quality it is desired for the absolute tocotrienol concentration to be highest, tocopherol to be the lowest, and the process used to be solvent-free. Annatto tocotrienol has the highest tocotrienol concentrations, and is tocopherol-free.
Vitamin E, be it tocopherols or tocotrienols, is extremely sensitive towards heat.
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