Rice bran tocopherols

XU z, HUA N, GODBER s (2001) Antioxidant activity of tocopherols, tocotrienols, and y-oryzanol components from rice bran against cholesterol oxidation accelerated by 2, 2 -azobis(2-methylpropionamidine) dihydrochloride. J Agri Food Chem, 49 2077-81. 

Determination of vitamin E isomers in seeds and nuts Determination of tocopherol and tocotrienol in rice bran Investigation of vitamin E content in olives Determination of tocopherol and tocotrienol in olive oils... 

Determination of tocopherols in vegetable oils Determination of tocopherols and tocotrienols in rice bran Determination of tocopherols in tomato... 

Figure D1.5.3 Chromatogram of tocopherols and tocotrienols of rice bran oil in normal-phase HPLC (see Basic Protocol). p-Tocopherol was below the level of detection.

In normal-phase HPLC on a silica column, the order of elution of tocopherols and tocotrienols is a-tocopherol, a-tocotrienol, [3-tocopherol, (3-tocotrienol, y-tocopherol, y-tocotrienol, 8-tocopherol, and 5-tocotrienol. Figure Dl.5.3 is an example of a normal-phase chromatograph of tocopherols and tocotrienols in rice bran oil. 

Bran, tocopherols/tocotrienols in rice bran oil, 488 (figs.)... 

Reversed-phase high-performance liquid chromatography (RP-HPLC), cholesterol measurement, 456-458 Rhamnogalacturonanas, 735 Rice bran oil, tocopherols/tocotrienols in, 488 (figs.)... 

Fig. 13 HPLC of vitamin E. (A) Standards of vitamin E vitamers. Column, 5-p.m Supelcosil LC-Si (250 X 4.6-mm ID) mobile phase, isooctane/ethyl acetate (97.5 2.5), 1.6 ml/min fluorescence detection, excitation 290 nm, emission 330 nm. Peaks (1) a-tocopherol (2) a-tocotrienol (3) /3-tocopherol (4) y-tocopherol (5) /3-tocotrienol (6) y-tocotrienol (7) 5-tocopherol (8) 5-tocotrienol. (B) Saponified rice bran sample. Chromatographic conditions as in (A) except for mobile phase isooctane/ethyl acetate/2,2-dimethoxypropane (98.15 0.9 0.85 0.1). (From Ref. 228. AOCS Press.)...

There are a number of minor oils, all of high value, most of which are marketed mainly either for medical purposes or for their flavour. Olive, evening primrose, borage, fish oils and cocoa butter are described elsewhere. Others include hazelnut, walnut, macadamia, almond, apricot, pumpkin, poppy-seed and rice bran oils. The process of testing for authenticity of these oils should be approached in the same way as for the bulk oils above, i.e. fatty acid profile, sterols, tocopherols and triglyceride composition. However, there is little generally available published material on the ranges of values to be expected... 

Experimentally, anti-oxidants such as gallic acid, ethyl gallate, oat flour (Findlay and Smith, 1945), sorbitan monostearate, glycerol monostearate, polyoxyethylene sorbitan monostearate (Hibbs and Ashworth, 1951), ascorbyl palmitate, dodecyl gallate (Abbot, 1971), high-oryzanol rice bran oil - containing tocopherols and tocotrienols (Nanua et al, 2000), nordihy-droguaiaretic acid, butylated hydroxyanisol, butylated hydroxy toluene and citric acid (Helal et al., 1976) have been used to enhance the oxidative stability of milk powders. 

Stdggl, W. Huck, C. Wongyai, S. Scherz, H. Bonn, G. 2005. Simultaneous determination of carotenoids, tocopherols and, y-oryzanol in crude rice bran oil by liquid ehromatography eoupled to a diode array and mass spectrometric detection employing silica C30 stationary phases. J. Sep. Sci. 28 1712-1718. 

Lipases liberated from the testa and the cross cells promote rapid hydrolysis of the oil, and therefore, it should be extracted within hours of milling. Attempts have been made to upgrade oil with 30% free acid by reaction with glycerol and the enzyme Lipozyme Mucor miehei lipase) followed by neutralization. The major acids in rice bran oil are palmitic (12-18%, typically 16%) oleic (40-50%, typically 42%), and linoleic acid (29 2%, typically 37%). The oil contains phospholipids ( 5%), a wax that may be removed and finds industrial use, and unsaponifiable matter including sterols, 4-methylsterols, triterpene alcohols, tocopherols, and squalene among others. 

Refined rice bran oil is an excellent salad oil and frying oil with high oxidative stability resulting from its high level of tocopherols and from the presence of the oryzanols (ferulic acid esters of sterols and triterpene alcohols). The oxidative stability of this oil is exploited in Good Fry Oil. This is a frying oil based on oleic-rich sunflower oil to which is added up to 6% of rice bran and/or sesame oil to confer high oxidative stability. Rice bran oil also finds several nonfood uses (45). 

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. 

TABLE 3. Tocopherol and Tocotrienol Concentrations (mg/100g) in Raw Rice Bran and Commercially Available Refined Oil (14). 

The tocopherol and tocotrienol contents of selected vegetable oils are shown in Table (7). Seed oils are mostly dominated by y- or a-tocopherol, but high levels of 5-tocopherol especially characterize soybean oil, which is the richest and commercially the most used source of tocopherols (46). Rice bran and pahn oils, on the other hand, represent the important sources of tocotrienols (45, 47). Rapeseed... 

Together with y-oryzanol, tocotrienols are responsible for the cholesterol-lowering effect of rice bran oil (250). Tocotrienol concentrates have been shown to have a hypocholesterolemic effect in animals and humans (251-257) possibly because of inhibition of hepatic 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase) (251, 258, 259). The presence of a-tocopherol at concentrations >20% in tocotrienol concentrates was, however, found to attenuate the inhibitory elfect of tocotrienols on HMG-COA reductase, thereby weakening their cholesterollowering activities (254). Tocotrienols were especially found to synergize the cholesterol-lowering effect of lovastatin (254). In addition, tocotrienols have been shown to influence certain hemostatic parameters and to reduce the occurrence of chemical-induced tumors in the rat (253). 

Supercritical CO2 column fractionation of soybean (57, 86, 88, 89) and rice bran oil (57) deodorizer distillates has been investigated to enrich their sterol and tocopherol contents. Brunner et al. (89) reported that the FFA were enriched in the top (in the extract), whereas the monoacylglycerols, tocopherols, and diacylglycerols were enriched in the bottom (in the raffinate) fraction during the fractionation of soybean oil deodorizer distillate. Saure and Brunner (88) achieved a tocopherol concentration of more than 70% (w/w) using continuous column fractionation of soybean deodorizer distillate where squalene was almost completely found in the top product, whereas sterols and tocopherols were enriched in the bottom product. King and Dunford (57) developed a two-step column fractionation scheme (13.6 MPa and 27.2 MPa at 313 K) for the enrichment of phytosterols from soybean and rice bran oil deodorizer distillates such that the FFA were removed in the first step and sterols were enriched in the oil fraction in the second step. 

Oil extracted from rice bran and com fiber is especially rich in tocopherols, tocotrienols and sterols. Extraction of these valuable compounds is remarkably enhanced by heat pretreatment (Lane et al., 1999). For example, the level of extracted y-tocophcrol increased from 0.3% to 3.6% by subjecting com fiber to temperatures of 100-175°C (Moreau et al., 1999). Tocopherol- and tocotrienol-rich oils may be used as such as important sources of vitamin E, or the vitamers can be purified from them following the same protocols as above. 

For identification of tocopherols and tocotrienols after chromatographic separation, pure tocopherols and tocotrienol mixtures are commercially available. Their purity can be checked by both HPLC and GC and the concentration of stock solutions by UV spectroscopy (Table 1.6). It is common to use lipid extracts from cereals and rice bran and their mixtures with pure compounds and vegetable oils to tentatively identify the vitamers and to study the performance of the HPLC separation. 

NuTriene [Eastman]. TMforaneutraceuti-cal supplement. A mixture of naturally occurring tocotrienols and tocopherols are extracted and concentrated from rice bran oil, a common cooking oil in Asia. 

Oryzanols are natural antioxidants having phenolic hydroxyl groups similar to tocopherols. The y-oryzanol content in the by-products is reported in Table 1. The highest amount of y-oryzanol (18 mg per g of rice bran oil, sample XI) was... 

The byproducts of rice-bran oil refining include waxes, lecithin, soap-stock (containing high-value oryzanol), and deodoriser distillate containing sterols, tocopherols, tocotrienols and squalene. The characteristics and physical properties of purified rice wax are similar to camauba wax (Sayre and Saunders... 

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