Tocotrienol

Tocotrienols – together with tocopherols – compose the vitamin E family. Natural tocotrienols exist in four different forms or isomers, named alpha-, beta-, gamma- and delta- tocotrienol, which contain different number of methyl groups on the chromanol ring. Although all the isomers are important antioxidants due to the ease of donating a hydrogen atom from the hydroxyl group on the chromanol ring to reduce free radicals, each of them has its own biological activity. Furthermore, many studies on test-tube scale indicate that tocotrienols have an anti-cancer effect, especially against skin and breast cancer for the extra three unsaturated bond.

R1 R2 R3 alpha Tocotrienol Me Me Me beta Tocotrienol Me H Me gamma Tocotrienol Me Me H delta Tocotrienol Me H H

Comparison of tocotrienol and tocopherol

Both tocotrienols and tocopherols, whose derivatives are in eight different isoforms, belong to vitamin E. However, tocotrienols are supposed to be more potent in their anti-oxidation and anti-cancer effect compared with the common forms of tocopherol due to the significant differences in the chemical structures. The unsaturated side-chain in tocotrienols makes them penetrate into tissues with saturated fatty layers more efficiently, hence, having stronger antioxidant properties which endow tocotrienols with a potential use in cosmetics. Commercial tocotrienols and tocopherols are mainly obtained from natural sources, such as palm or rice bran oil.

Natural tocotrienols

Food sources: Palm oil is the largest natural source of tocotrienols. Other good sources are rice bran oil, and coconut oil. Other food sources include cereal grains, such as barley, oats, and rye.

Tocotrienols can be obtained from natural sources using general procedures, labelled as ‘d-tocotrienols’. Tocotrienols concentrates and isomers can be obtained through purification processes. These procedures are intricate and difficult to do on a large scale. However, some companies may have achieved a breakthrough in isolating and purifying natural tocotrienols.

Synthetic tocotrienols

Tocotrienols can be synthesized through chemical reactions, labelled as ‘dl-tocotrienols’. Chemically synthesized tocotrienols consist of both normal and its laterally inverted compounds, which are mirror-reflection of each other. The left version has the same structure but laterally inverted compared to right version. Only the right version has the bioavailability; therefore, synthetic compounds are said to have half bioactivity as much as the natural form.

The benefits of tocotrienols

Antioxidant activity

Antioxidants include polyphenols, lipoic acid, carotenoids, and tocotrienols. These 'nutraceuticals' have demonstrated greater antioxidant and anti-cancer activity than what has been achieved previously in nutritional protocols and cosmetics formula. The benefits of tocotrienols reach from decreasing plateletaggregation (clumping of blood) to anti-inflammatory action and anti-cancer activity.

Tocotrienols show considerably superior antioxidant properties compared to dl-α-Tocopherol in clinical and experimental studies due to their better distribution in the fatty layers of the cell membrane. The tocotrienol unsaturated side chain allows for a more efficient penetration into saturated fatty layers of the brain and liver. In addition to the free radical scavenging effect, the antioxidant function of tocotrienols is also associated with lowering tumor formation, DNA damage and cell damage. Studies in animals explored the effects of long-term administration of tocotrienols on liver cancer. Supplementation of tocotrienols in rats induced with a potent liver cancer agent demonstrated that the tocotrienols prolonged the impact of the cancer agent. Cell damage to the liver was significant in the untreated group versus the tocotrienol treated group.

Tocotrienols and breast cancer

A study showed that tocotrienols are the components of vitamin E responsible for growth inhibition in human breast cancer cells in vitro as well as in vivo through estrogen-independent mechanisms. Tocotrienols can also affect cell homeostasis, possibly independently of their antioxidant activity.Nesaretnam K, Ambra R, Selvaduray KR, et al. (2004). Tocotrienol-rich fraction from palm oil and gene expression in human breast cancer cells. ANNALS OF THE NEW YORK ACADEMY OF SCIENCES 1031: 143-157. Anti-cancer effects of α- and γ-tocotrienol have been reported, although δ-tocotrienol was verified to be the most effective tocotrienol in inducing apoptosis (cell death) in estrogen-responsive and estrogen-nonresponsive human breast cancer cells. A daily dose of 30 - 50 mg mixture of α- and γ-tocotrienols can reduce breast cancer risk, and a treatment plan for breast cancer should use higher dosage.

Tocotrienols and prostate cancer

Investigation of the antiproliferative effect of tocotrienols in PC3 and LNCaP prostate cancer cells suggests that the transformation of vitamin E to CEHC is mostly a detoxification mechanism, useful to maintain the malignant properties of prostate cancer cells.Conte C, Floridi A, Aisa C, et al. (2004). Gamma-Tocotrienol metabolism and antiproliferative effect in prostate cancer cells. ANNALS OF THE NEW YORK ACADEMY OF SCIENCES 1031: 391-394.

Tocotrienols and cholesterol reduction

The development of new cholesterol-lowering agents has been given more and more attention by pharmaceutical companies due to the strong relationship between cholesterol and atherosclerosis. Tocotrienols, especially δ- and γ-tocotrienols, were shown to be effective nutritional agents to treat high cholesterol in recent research programs. In particular, γ-tocotrienol appears to act on a specific enzyme called 3-hydroxy-3-methylglutaryl-coenzyme and suppressed the production of this enzyme, which results in less cholesterol being manufactured by liver cells.

The investigation of the cholesterol-lowering effects of tocotrienols in cholesterol-fed rabbits found that the cholesterol in plasma decreased following gamma-tocotrienol treatment (-22%) after 6 weeks. The decrease was mainly attributable to a reduction in LDL cholesterol (23%).Hasselwander O, Kramer K, Hoppe PP, et al. (2002). Effects of feeding various tocotrienol sources on plasma lipids and aortic atherosclerotic lesions in cholesterol-fed rabbits. FOOD RESEARCH INTERNATIONAL 35 (2-3): 245-251.

Tocotrienols and diabetes

Investigation of the intake of antioxidants for its ability to prevent type 2 diabetes shows that vitamin E intake was significantly associated with a reduced risk of type 2 diabetes. The relative risk (RR) of type 2 diabetes between the extreme quartiles of the intake was 0.69 (95% CI 0.51-0.94, P for trend=0.003). Intakes of alpha-tocopherol, gamma-tocopherol, delta-tocopherol, and beta-tocotrienol were inversely related to a risk of type 2 diabetes. Thus the development of type 2 diabetes may be reduced by the intake of antioxidants in the diet.Montonen J, Knekt P, Jarvinen R, et al. (2004). Dietary antioxidant intake and risk of type 2 diabetes. DIABETES CARE 27 (2): 362-366.

References

External links

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