Tocotrienol

Source: Wikipedia, the free encyclopedia.
Not to be confused with the more common class of molecules that are also forms of vitamin E, the tocopherols.
General chemical structure of tocotrienols. alpha(α)-Tocotrienol: R1 = Me, R2 = Me, R3 = Me; beta(β)-Tocotrienol: R1 = Me, R2 = H, R3= Me; gamma(γ)-Tocotrienol: R1 = H, R2 = Me, R3= Me; delta(δ)-Tocotrienol: R1 = H, R2 = H, R3= Me

The vitamin E family comprises four tocotrienols (alpha, beta, gamma, delta) and four

isoprenoid side chains with three carbon-carbon double bonds versus saturated side chains for tocopherols (see Figure).[1][2]

Tocotrienols are compounds naturally occurring at higher levels in some

saw palmetto, annatto, and certain other types of seeds, nuts and grains, and the oils derived from them.[3][4]

Chemically, different analogues of vitamin E all show some activity as a chemical

free radical and reactive oxygen species. Historically studies of tocotrienols account for less than 1% of all research into vitamin E.[7]

Health effects

A number of health benefits of tocotrienols have been proposed, included decreased risk of heart disease and cancer.

United States National Academy of Sciences does not define a Recommended Dietary Allowance or Adequate Intake for tocotrienols.[9]

Brain

A review of human studies in middle-aged and elderly stated "Evidence from prospective and case-control studies suggested that increased blood levels of tocotrienols were associated with favorable cognitive function outcomes." The review qualified this statement by noting that randomized, controlled clinical trials were needed to evaluate these observations.[10]

Heart disease

Tocotrienols have been linked to improved markers of

heart disease.[8][11]

Skin

Tocotrienols have been linked to improve

atopic eczema.[8][12]

Side effects

Tocotrienols are generally well tolerated and without significant side effects.[8]

History

The discovery of tocotrienols was first reported by Pennock and Whittle in 1964, describing the isolation of tocotrienols from rubber.

palm.[16] Other natural tocotrienol sources include rice bran oil, coconut oil, cocoa butter, barley, and wheat germ.[17] Tocotrienols are safe and human studies show no adverse effects with consumption of 240 mg/day for 48 months.[18] 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.

Etymology

Tocotrienols are named by analogy to tocopherols (from Greek words meaning to bear a pregnancy (see tocopherol); but with this word changed to include the chemical difference that tocotrienols are trienes, meaning that they share identical structure with the tocopherols except for the addition of the three double bonds to their side chains.

Comparison to tocopherols

Tocotrienols have only a single

levorotatory; l-tocotrienol) forms of tocotrienols could exist as well, which would have a 2S rather than 2R configuration at the molecules' single chiral center, but unlike synthetic, dl-alpha-tocopherol, the marketed tocotrienol dietary supplements are all d-tocotrienol extracts from palm or annatto oils.[citation needed
]

Tocotrienol studies confirm anti-oxidation,[19] anti-inflammatory potentials and suggest anti-cancer effects[20][21] better than the common forms of tocopherol due to their chemical structure. Scientists have suggested tocotrienols are better antioxidants than tocopherols.[22][23][24][25] It has been proposed that the unsaturated side-chain in tocotrienols causes them to penetrate tissues with saturated fatty layers more efficiently than tocopherol.[26] Lipid ORAC values are highest for δ-tocotrienol.[27] However that study also says: "Regarding α-tocopherol equivalent antioxidant capacity, no significant differences in the antioxidant activity of all vitamin E isoforms were found."

Metabolism and bioavailability

The metabolism and thus the bioavailability of tocotrienols are not well understood and simply increasing the intake of tocotrienols might not increase tocotrienol levels in the body.[6]

α-Tocopherol interference

Various studies have shown that alpha-tocopherol interferes with tocotrienol benefits.[6] High levels of α-tocopherol increase cholesterol production.[28] α-Tocopherol interference with tocotrienol absorption was described previously by scientists, who showed that α-tocopherol interfered with absorption of α-tocotrienol, but not γ-tocotrienol.[29] Finally, α-tocopherol was shown to interfere with tocotrienols by increasing catabolism.[30]

Sources

In nature, tocotrienols are present in many plants and fruits. The oil palm fruit (

alpha-tocotrienol and delta-tocotrienol. Other cultivated plants high in tocotrienols includes rice, wheat, barley, rye and oat.[31]

Research

Radiation countermeasures

Following exposure to

U.S. Armed Forces Radiobiology Research Institute (AFRRI) found that treatment with γ-tocotrienol or δ-tocotrienol enhanced survival of hematopoietic stem cells, which are essential for renewing the body's supply of blood cells.[32][33] Based on these successful results of studies in mice, γ-tocotrienol is being studied for its safety and efficacy as a radioprotective measure in nonhuman primates.[34]
No human trials have yet been completed.

Further reading

  • Tan B, Watson RR, Preedy VR, eds. (2013). Tocotrienols: Vitamin E Beyond Tocopherols (2nd ed.). Boca Raton: CRC Press. ISBN 9781439884416.

References

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External links
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