Palm tocotrienols

The effect of tocotrienols on cancer progression was evaluated by Komi-yama and Yamaoka (177). The antitumor activity of tocotrienols was evaluated in terms of the increase in the lifespan of mice inoculated with tumor cells. a-Tocotrienols and y-tocotrienols were effective against the sarcoma cancer cell lines and Ehrlich carcinoma. When human lung carcinomas were challenged with these tocotrienols, a cytotoxic activity due to the tocotrienols was exhibited. Similarly. DMBA-treated rats responded with lower tumor numbers when their diets were supplemented with palm tocotrienols (178). Recently, a-carotene isolated from pahn oil has been shown to have antitumor activity against mouse lung cancer and against skin cancer (179). 

Vegetable oils, especially the seed oils, are rich sources of tocopherols. Refining waste from the edible oil industry has emerged as an important raw material for the extraction of vitamin E, and the residues of the soybean refining industry are one such source. Tocotrienols, on the other hand, are found predominantly in palm oil and in cereals such as barley and rice bran oils. With the emergence of palm oil as the second largest edible oil in world markets, technological advances have been made to similarly extract tocotrienol-rich palm vitamin E from the refinery wastes of the industry. The resultant product, often termed palm tocotrienol-rich fraction (TRF), is currently available on a commercial scale from Malaysia. A similar tocotrienol-rich vitamin E preparation derived from rice bran oil is also available in the U.S. 

Hayes et al. reported the presence of tocotrienols in all tissues except the brain of hamsters fed palm tocotrienols, with adipose tissue being especially rich in its ability to accumulate appreciable amounts of tocotrienols. The presence of a- and y-tocotrienols has been reported, even when the diet was not especially enriched with tocotrienols. Skin has been suggested to be an important storage and excretory site for vitamin E, and the accumulation of tocotrienols could be especially beneficial in protecting the lipid barrier of the stratum comeum. ... 

Black, T.M., Wang, P, Maeda, N., and Coleman, R.A., Palm tocotrienols protect ApoE + - mice from diet-induced atheroma formation, J. Nutr. 130 (10), 2420-2426, 2000. 

Das, S., Powell, S.R., Wang, R, Divald, A., Nesaretnam, K., Tosaki, A., Cordis, G.A., Maulik, N., and Das, D.K., Cardioprotection with palm tocotrienol antioxidant activity of tocotrienol is linked with its ability to stabilize proteasomes. Am. J. Physiol. Heart Circ. Physiol, 289(1), H361-367, 2005. 

Tocopherols (and tocotrienols) in an oil can also be useful, though the absolute, and in some cases the relative, levels of each can be affected by age and refining. These are usually determined by HPLC. The tocotrienols are of particular importance, as they are present in significant amounts only in corn, grapeseed, palm and palm kernel oils. The presence of y-tocopherol in an oil that is not expected to contain significant levels, or else the presence of it in excess to that expected, would indicate that another oil is present, and the most likely suspect oil would be soyabean. The tocopherol profile is, however, usually only of use as confirmation, together with other analyses. 

Tocopherols and tocotrienols are precursors of vitamin E and are important antioxidants in oils. Their reactivity means that they are not stable to many oil processing procedures, including deodorization, which reduces levels by up to 15%. Levels of tocopherols in cocoa butter are usually about 100-300 mg/kg, with the y-isomer (IV) being the major component (about 90%), but they can be entirely absent (Lipp et al., 2001) (Figure 3.3). Tocotrienols have a similar structure with unsaturation of alternate bonds along the alkyl chain. Only y-tocotrienol is found in cocoa butter and this at low levels (< 5 mg/kg). Palm oil is notably high in tocopherols and tocotrienols, of which a-tocopherol and a-tocotrienol make up 20% to 30% each with most of the remainder as y-tocotrienol. 

In some cases, analysis of tocopherols can be used to detect adulteration of oil. Both palm oil and grapeseed oil are relatively unusual in containing significant levels of tocotrienols, which are absent or present at much lower levels in most vegetable oils (Table 6.3). Detection of these compounds can be used to identify adulteration in olive oil at levels as low as 2% (Dionisi et al., 1995). 

PLE extraction with hexane (80 °C, 1500 psi, one extraction cycle of 10 min) was used to successfully extract tocols from palm-pressed fiber (Sanagi et ah, 2005). Contents and standard deviations of a-tocopherol and a-trienol, and y- and 5-tocotrienols were comparable to those from Soxhlet extraction extraction time with the PLE method was reduced to only 25 min and solvent usage to 45 ml, whereas those with Soxhlet extraction were 8 h and 200 ml. Hexane under PLE conditions has also been used to extract tocols from lyophilized nuts (Sivakumar et ah, 2005) and grape seeds (Freitas et ah, 2008), and always gave higher yields than Soxhlet extraction. 

Several reversed-phase HPLC methods have also been reported for the quantitative analysis of tocopherols and tocotrienols (Table 11.6). To be able to separate all eight tocols a pentafluorophenylsilica column (Abidi, 2003) was used. A C30-bonded phase silica column separated the three tocotrienols, a-tocopherol, and a-tocomonoenol in palm oil (Ng et al., 2004). C30-bonded silica columns have also been used to simultaneously analyze tocopherols, other fat-soluble vitamins, and carotenoids (Gentili and Caretti, 2011). 

Palmitic Acid Oils The commodity oil richest in palmitic acid is pahn oil (44%). This oil is also rich in oleic acid (37%), contains lower levels of linoleic acid (10%), and is a valuable source of minor components, especially carotenes, toco-pherols, and tocotrienols (Section 3). Palm oil is an important world commodity in feeding the developing world. It is fractionated extensively to give a wider range of uses as palm olein and palm stearin. The only other commodity oil with a significant level of palmitic acid is cottonseed oil (27%). 

The supply of palm oil has risen considerably since around 1980. It was almost 24 million tons per annum in 2001-2002 and is predicted to exceed the production of soybean oil during the period 2011-2015 at around 37 milhon tons. The oil contains almost equal proportions of saturated (palmitic 48% and stearic 4%) and unsaturated acids (oleic 37% and hnoleic 10%). The major triacylglycerols are POP (30-40%) and POO (20-30%). The oil is used mainly for food purposes but finds some nonfood uses. It is a source of valuable byproducts such as carotene and tocopherols and tocotrienols (vitamin E). Red palm oil is a carefully prepared oil that retains about 80% (500-700 ppm) of the carotenes present in the crude oil and is a valuable dietary source of these important compounds (42). 

Tocopherols and tocotrienols, collectively known as tocols, are monophenolic and lipophilic compounds that are widely distributed in plant tissues (7). The main commercial source of natural tocopherols is the soybean oil. Tocotrienols, less common than tocopherols, are present in palm oil, rice bran oil, as well as cereals and legumes (11). Tocopherols and tocotrienols are classified into a-, (3-, y-, and 5-, depending on their chemical structures (Figure 7). In general, tocotrienols have a stronger antioxidant effect on lipid oxidation than tocopherols. The antioxidant activity of tocopherols is dependent on temperature and is in the order of 5- > y->P-> oc-tocopherol (7). Tocopherols (mixed natural concentrate) are a golden... 

The dominance of tocopherols, namely, alpha-, beta-, gamma-, and delta- and the corresponding tocotrienols, depends on the type of oil under investigation. Thus, tocotrienols occur primarily in palm and rice bran oils. Meanwhile, tocopherols are more widely present in different oils. However, their proportions in different oils is dependent on the source material. As an example, sunflower oil contains mainly alpha-tocopherol and very small amounts of other tocopherols, whereas soybean oil contains mainly gamma-tocopherol with decreasing amounts of delta-, alpha-, and beta-tocopherols as determined by high-performance liquid chromatography. 

Cmde palm oil contains tocopherols and tocotrienols in the range of 600-1000 ppm. Refined palm oil retains about 50% of these products. Tocopherols and tocotrienols are antioxidants and provide some natural oxidative protection to the oil. Table 8 shows the types of tocopherols and tocotrienols present in palm oil. 

From Table 8, it can be seen that ot-tocopherols and y-tocotrienols account for the major portion of the total tocopherols and tocotrienos present in palm oil. Gapor (9) confirms the presence of the above-listed tocopherols and tocotrienols by high-performance liquid chromatography (HPLC) and also indicated the probable presence of the esterified forms. 

The combined effects of the properties of the carotenoids, tocopherols, tocotrienols and the 50% unsaturation of the acids confer on palm oil a higher oxidative stability as compared to a lot of other vegetable oils. 

---