Natural Tocotrienols

F. Antioxidant and Other Properties

• 1. Free radical recycling and intramembrane mobility in the antioxidant properties of alpha-tocopherol and alpha-tocotrienol

  Serbinova, E. et al. (1991). Free Radical Recycling and Intramembrane Mobility in the Antioxidant Properties of Alpha-tocopherol and Alpha-tocotrienol. Free Radical Biology & Medicine, 10(5) : 263- 275.

  d-Alpha-tocopherol (2R,4'R,8'R-Alpha-tocopherol) and d-alpha-tocotrienol are two vitamin E constituents having the same aromatic chromanol "head" but differing in their hydrocarbon "tail": tocopherol with a saturated and toctrienol with an unsaturated isoprenoid chain. d-Alpha-tocopherol has the highest vitamin E activity, while d-alpha-tocotrienol manifests only about 30% of this activity. Since vitamin E is considered to be physiologically the most important lipid-soluble chain-breaking antioxidant of membranes, we studied alpha-tocotrienol as compared to alpha-tocopherol under conditions which are important for their antioxidant function. d-Alpha-tocotrienol possesses 40-60 times higher antioxidant activity against (Fe2+ + ascorbate)- and (Fe2+ + NADPH)-induced lipid peroxidation in rat liver microsomal membranes and 6.5 times better protection of cytochrome P-450 against oxidative damage than d-alpha-tocopherol. To clarify the mechanisms responsible for the much higher antioxidant potency of d-alpha-tocotrienol compared to d-alpha-tocopherol, ESR studies were performed of recycling efficiency of the chromanols from their chromanoxyl radicals. 1H-NMR measurements of lipid molecular mobility in liposomes containing chromanols, and fluorescence measurements which reveal the uniformity of distribution (clusterizations) of chromanols in the lipid bilayer. From the results, we concluded that this higher antioxidant potency of d-alpha-tocotrienol is due to the combined effects of three properties exhibited by d-alpha-tocotrienol as compared to d-alpha-tocopherol: (i) its higher recycling efficiency from chromanoxyl radicals, (ii) its more uniform distribution in membrane bilayer, and (iii) its stronger disordering of membrane lipids which makes interaction of chromanols with lipid radicals more efficient. The data presented show that there is a considerable discrepancy between the relative in vitro antioxidant activity of d-alpha-tocopherol and d-alpha-tocotrienol with the conventional bioassays of their vitamin activity.

• 2. Palm Oil Vitamin E Protects Against Ischemia/Reperfusion Injury in the Isolated Perfused Langendorff Heart

  Serbonova, E. et al. (1992). Palm Oil Vitamin E Protects Against Ischemia/Reperfusion Injury in the Isolated Perfused Langendorff Heart. Nutrition Research, Suppl.1 : S203-S215.

  We studied the effect of palm oil vitamin E on Langendorff perfused rat hearts subjected to 40 minutes of global ischemia. Our results demonstrated that palm oil vitamin E was more efficient in the protection of isolated Langendorff heart against ischemia/reperfusion injury than tocopherol as measured by its mechanical recovery. Palm oil vitamin E completely suppressed LDH enzyme leakage from ischemic hearts, prevented the decrease in ATP and creatine phosphate levels and inhibited the formation of endogenous lipid peroxidation products. Our data indicate that a palm oil vitamin E mixture containing both alpha-tocopherol and alpha-tocotrienol may be more efficient than alpha-tocopherol alone in the protection of the heart against oxidative stress induced by ischemia-reperfusion.

• 3. Molecular Aspects of alpha-Tocotrienol Antioxidant Action and Cell Signaling

  Packer, L. et al. (2001). Molecular Aspects of alpha-Tocotrienol Antioxidant Action and Cell Signaling. J. Nutr. 131 : 369S-373S.

  Vitamin E, the most important lipid-soluble antioxidant, was discovered at the University of California at Berkeley in 1922 in the laboratory of Herbert M. Evans (Science 1922, 55: 650). At least eight vitamin E isoforms with biological activity have been isolated from plant sources. Since its discovery, mainly antioxidant and recently also cell signaling aspects of tocopherols and tocotrienols have been studied. Tocopherols and tocotrienols are part of an interlinking set of antioxidant cycles, which has been termed the antioxidant network. Although the antioxidant activity of tocotrienols is higher than that of tocopherols, tocotrienols have a lower bioavailability after oral ingestion. Tocotrienols penetrate rapidly through skin and efficiently combat oxidative stress induced by UV or ozone. Tocotrienols have beneficial effects in cardiovascular diseases both by inhibiting LDL oxidation and by down-regulating 3-hydroxyl-3-methylglutaryl-coenzyme A (HMG CoA) reductase, a key enzyme of the mevalonate pathway. Important novel antiproliferative and neuroprotective effects of tocotrienols, which may be independent of their antioxidant activity, have also been described.

• 4. Effect of gamma-tocotrienol on blood pressure, lipid peroxidation and total antioxidant status in spontaneously hypertensive rats (SHR)

  Newaz, M. A. et al. (1999). Effects of gamma-Tocotrienol on Blood Pressure, Lipid Peroxidation, and Total Antioxidant Status in Spontaneously Hypertensive Rats (SHR). Clin. And Exp Hypertens. 21(8) : 1297-1313.

  The aim of this study was to determine the effects of gamma tocotrienol on lipid peroxidation and total antioxidant status of spontaneously hypertensive rats (SHR), comparing them with normal Wistar Kyoto (WKY) rats. SHR were divided into three groups and treated with different doses of gamma tocotrienol (gamma1, 15 mg/kg diet; gamma2, 30 mg/kg diet and gamma3, 150 mg/kg diet). Normal WKY and untreated SHR were used as normal (N) and hypertensive control (HC). Blood pressure were recorded every fortnightly for three months. At the end of the trial, animals were killed and measurement of plasma total antioxidant status, plasma superoxide dismutase (SOD) activity and lipid peroxide levels in plasma and blood vessels were carried out following well established methods. Study shows that lipid peroxides were significantly higher in hypertensive plasma and blood vessels compared to that of normal rats (Plasma- N: 0.06+/-0.01, HC: 0.13+/-0.008; p<0.001, B1. Vessels - N: 0.47+/-0.17, HC: 0.96+/-0.37; p<0.001). SOD activity was significantly lower in hypertensive than normal rats (N = 148.58+/-29.56 U/ml, HC = 110.08+/-14.36 U/ml; p = 0.014). After three months of antioxidant trial with gamma-tocotrienol, it was found that all the treated groups have reduced plasma lipid peroxides concentration but was only significant for group gamma1 (gamma1: 0.109+/-0.026, HC: 0.132+/-0.008; p = 0.034). On the other hand, lipid peroxides in blood vessels reduced significantly in all treated groups (gamma1; p<0.05, gamma2; p<0.001, gamma3; p<0.005). All the three treated groups showed improve total antioxidant status (p<0.001) significantly. SOD activity also showed significant improvement in all groups (gamma1: p<0.001, gamma2: p<0.05, gamma3: p<0.001). Correlation studies showed that, total antioxidant status (TAS) and SOD were significantly negatively correlated with blood pressure in normal rats (p = 0.007; p = 0.008) but not in SHR control. This correlation regained in all three groups SHR's after treatment with tocotrienol. Lipid peroxides in blood vessel and plasma showed a positive correlation with blood pressure in normal and SHR control. This correlation also remains in treated groups significantly except that in gamma3 where positive correlation with plasma lipid peroxide was not significant. In conclusion it was found that antioxidant supplement of gamma-tocotrienol may prevent development of increased blood pressure, reduce lipid peroxides in plasma and blood vessels and enhanced total antioxidant status including SOD activity.

• 5. Antioxidant Activities of Palm Vitamin E with Special Reference to Tocotrienols

  Gapor, A. B. et al. (1990). Antioxidant Activities of Palm Vitamin E with Special Reference to Tocotrienols.Elaeis. 1(1) : 63-7.

  The antioxidant activities of palm vitamin E and tocotrienols (T3) from Elaeis guineensis were investigated in model systems using distilled palm methyl ester (DME) and vitamin E free RBD palm olein respectively. Oxidative stability was measured by the Rancimat method. Addition of 500 ppm vitamin E concentrate, which consisted of α-tocopherol (21.9%), α-tocotrienol (31.1%), γ-tocotrienol (37.7%) and δ-tocotrienol (9.3%) in DME was found to increase the oxidative stability of the substrate by a factor of about 2.6. Vitamin E free RBD palm olein was found to be relatively unstable. Addition of 200-2000 ppm of α-tocotrienol, γ-tocotrienol and δ-tocotrienol individually to vitamin E free RBD palm olein showed that these compounds were effective antioxidants and that the activity increased with increasing concentration. At 200 ppm, α-tocotrienol improved the stability of the substrate by a factor of about 6.3. The order of antioxidant activities of tocotrienols was found to be γ-T3 ≥ δ-T3 > α-T3 : γ-T3 had about twice the activity of α-T3.

• 6. Antioxidative Activities of α-Tocotrienol and Its Derivative in the Oxidation of Dilinoleoylphosphatidylcholine Liposomes

  Yamaoka, M. et al. (1989). Antioxidant Activities of alpha-Tocotrienols and Its Derivatives in the Oxidation of Dilinoleoylphosphatidylcholine Liposomes. J. Jpn. Oil Chem. Soc. 38(6) : 478-485.

  The antioxidative activity of α-tocotrienol (α-Toc 3) and its derivative was studied in the 2, 2'-azobis (2-amidinopropane) dihydrochloride (AAPH) initiated oxidation of dilinoleoylphosphatidylcholine (DLPC) lipo-somes. Two DLPC concentrations, 1.93×10-3M for total aqueous dispersion (condition-I) and around 0.3×10-3M for total aqueous dispersion (condition-II), were used, keeping the molar concentrations of antioxidants or initiator for DLPC constant. A kinetic study indicated that in DLPC bilayers, α-Toc 3 had the same anti-oxidative activity as α-tocopherol (α-Toc) at both concentrations. However, α-Toc 3 showed higher antioxidative activity than α-Toc when was added after liposome formation. The synthesized water-soluble derivative of α-Toc 3 added after DLPC liposome formation under condition-II, as well as water-soluble carboxy-2, 5, 7, 8-tetramethyl-6-chromanol, showed about the same antioxidative activity as α-Toc 3 mixed with DLPC prior to liposome formation under condition-II. Solubility in water was a factor determining the antioxidative activity of the water-soluble antioxidant under condition-II. It would thus appear that α-Toc3 shows higher antioxidative activity than α-Toc in vitro in the synthetic liposome system, and that this can be explained on the basis of the distribution of α-Toc 3 in, or in the vicinity of the DLPC bilayers.

• 7. Tocotrienols: constitutional effects in aging and disease

  Schaffer, S. et al. (2005). Tocotrienols: Constitutional effects in aging and disease. J. Nutr. 135(2) : 151-4.

  Tocotrienols, a class of vitamin E analogs, modulate several mechanisms associated with the aging process and aging-related diseases. Most studies compare the activities of tocotrienols with those of tocopherols ("classical vitamin E"). However, some biological effects were found to be unique for tocotrienols. Although the absorption mechanisms are essentially the same for all vitamin E analogs, tocotrienols are degraded to a greater extent than tocopherols. The levels of tocotrienols in the plasma of animals and humans were estimated to reach low micromolar concentrations. One hallmark in the origin of disease and aging is the overproduction of reactive oxygen species (ROS). Tocotrienols possess excellent antioxidant activity in vitro and have been suggested to suppress ROS production more efficiently than tocopherols. In addition, tocotrienols show promising nonantioxidant activities in various in vitro and in vivo models. Most notable are the interactions of tocotrienols with the mevalonate pathway leading to the lowering of cholesterol levels, the prevention of cell adhesion to endothelial cells, and the suppression of tumor cell growth. Furthermore, glutamate-induced neurotoxicity is suppressed in the presence of tocotrienols. This review summarizes the main antioxidant and nonantioxidant effects of tocotrienols and assesses their potential as health-maintaining compounds.

• 8. Mechanisms underlying the radioprotective properties of ɣ-tocotrienol: comparative gene expression profiling in tocol-treated endothelial cells

  Berbee, M. et al. (2011). Mechanisms underlying the radioprotective properties of γ-tocotrienol: comparative gene expression profiling in tocol-treated endothelial cells. Genes & Nutrition. 7: 75-81.

  Among the eight naturally occurring vitamin E analogs, γ-tocotrienol (GT3) is a particularly potent radioprophylactic agent in vivo. Moreover, GT3 protects endothelial cells from radiation injury not only by virtue of its antioxidant properties but also by inhibition of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase and by improving the availability of the nitric oxide synthase cofactor tetrahydrobiopterin. Nevertheless, the precise mechanisms underlying the superior radioprotective properties of GT3 compared with other tocols are not known. This study, therefore, examined the differences in gene expression profiles between GT3 and its tocopherol counterpart, γ-tocopherol, as well as between GT3 and α-tocopherol in human endothelial cells. Cells were treated with vehicle or the appropriate tocol for 24 h, after which total RNA was isolated and genome-wide gene expression profiles were obtained using the Illumina platform. GT3 was far more potent in inducing gene-expression changes than α-tocopherol or γ-tocopherol. In particular, GT3 induced multiple changes in pathways known to be of importance in the cellular response to radiation exposure. Affected GO functional clusters included response to oxidative stress, response to DNA damage stimuli, cell cycle phase, regulation of cell death, regulation of cell proliferation, hematopoiesis, and blood vessel development. These results form the basis for further studies to determine the exact importance of differentially affected GO functional clusters in endothelial radioprotection by GT3.

• 9. Tocotrienol enriched palm oil prevents atherosclerosis through modulating the activities of peroxisome proliferators-activated receptors

  Li, F. et al. (2010). Tocotrienol enriched palm oil prevents atherosclerosis through modulating the activities of peroxisome proliferators-activated receptors. Atherosclerosis. 211(1):278-282.

  PPalm oil is enriched in vitamin E in the form of α-, γ-, and δ-tocotrienols. Dietary tocotrienol supplements have been shown to prevent atherosclerosis development in patients and preclinical animal models. However, the mechanistic basis for this health beneficial effect is not well established. Peroxisome proliferator-activated receptors α, γ, and δ (PPARα, PPARγ, and PPARδ) are ligand regulated transcription factors that play essential preventive roles in the development of atherosclerosis through regulating energy metabolism and inflammation. In this study, we presented data that the tocotrienol rich fraction (TRF) of palm oil activated PPARα, PPARγ, and PPARδ in reporter based assays. Importantly, TRF attenuated the development of atherosclerosis in ApoE−/− mice through inducing PPAR target gene liver X receptor alpha (LXRα) and its down-stream target genes apolipoproteins and cholesterol transporters, suggesting that modulating the activities of PPARs is a key aspect of the in vivo action of tocotrienols.