Rice bran sterols

The sterols and sterolins in rice bran are potent immunomodulators. The best response was obtained with a 100 1 sterol/sterolin mixture that demonstrated T-cell proliferation from 20% to 920% and active cell antigens after four weeks in human subjects (Bouic et al, 1996). Another in vitro experimental study with sterol/sterolins, demonstrated a significant increase in cytokinines, interleukin-2 and y-interferon between 17% and 41 % in addition to an increase in natural killer cell activity. These experiments (Bouic et al, 1996) prove that sterol/sterolins are potent immunomodulators with important implications for the treatment of immune dysfunction. Rice bran products are excellent dietary supplements for the improvement of immune function. It is probable that the effects of rice bran on diabetes, CVD and cancer all result from improved immune function. 

AKIHISA T, YASUKAWA K, YAMAMURA M, UKIYA M, KIMURA Y, SHIMIZU N, ARAI K (2000) Tliterpene alcohol and sterol ferulates from rice bran and their anti-inflammatory effects. JAgri FoodChem, 48 2313-19. 

Major flaxseed sterols are stigmasterol, camp sterol, and 5-5 avenasterol (Daun et al., 2003). Obtusifoliol, gramisterol, and citrostadienol constituted 45%, 22%, and 12%, respectively, of the total 4a-monomethylsterol in flaxseed (Kamm et al., 2001). Squalene content of flaxseed oil was reported as 4 mg/100 g oil, which was significantly lower than olive, corn, and rice bran oils. Squalene content is an intermediate compound of biosynthesis of plant sterols, which may have protective effects on lipid quality. Squalene could act as a peroxy radical scavengers in high polyunsaturated fatty acid oil (Dessi et al., 2002). 

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... 

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). 

TABLE 4. Fatty Acids of Sterol and Alkyl Esters, Alcohols of Longer Alkyl Esters, and Alkanes and Alkenes of Rice Bran Waxy Lipids (24). 

Rice bran 4.2-5.2 y-oryzanol (cinnamic acid esters of sterols)... 

Sterol Coconut Corn Cotton Seed Linseed Olive Pam Palm Kernel Peanut Rape Seed Rice Bran Saf- flower Sesame Shea Butter Soy Bean Sun flower Wheat Germ... 

High aliphatic alcohols and wax esters in which aliphatic alcohols or sterols are esterified to fatty or phenolic acids are also present in cmde vegetable oils at low levels and are partially removed in the winterization process during oil refining. Waxes, mainly esters of long-chain saturated fatty acids and a monounsaturated alcohol, especially eicosenoic alcohol, are found in crude vegetable oils such as olive, sunflower, soybean or peanut but are absent from com or rice bran oils... 

There is some evidence that y-oryzanol present in rice bran oil lowers semm total- and LDL cholesterol as well (16, 185, 188). Butter from the Shea tree, Butyro-spermum parkii, contains a very high level of 4,4-dimethylsterols (about 8%) mostly as esters of cinnamic acid (oryzanols). Apparent absorption of these sterols, as estimated by their disappearance from feces, was found to be 27-52% in Wistar rat and 13-49% in humans (189). It was found that the cinnamic acid esters of the 4-desmethylsterols of rice bran oils, but not those of the 4,4 -dimethylsterols of shea nut oil possess hypolipidemic activity (190). 

The majority of the crude oils contain 1000-5000 ppm sterols. Exceptions are com and rice bran oil that may contain up to 1-2% of phytosterols (Table 9). 

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. 

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... 

Table 11.9 Sterols content and their percentage composition in rice-bran oil... 

The aleurone layers of com, wheat, rye, and triticale have a high percentage of samrated phytosterols (i.e., sitostanol and campestanol), which are esterified to ferulic acid (Figure 6.3), and to p-coumaric acid to a much lesser extent in com. Rice bran differs from most other cereals in having mostly 30- and 31-carbon sterols (triterpenoids) esterified to femlic acid and small amounts of typical sterols (Moreau et al., 1996). 

No effects of oryzanol (a derivative of rice bran oil that includes sterols and ferulic acid) on berberine absorption were observed in healthy volunteers (Li et al. 2000). 

The fatty acid spectrum of rice bran oil is 22-25% palmitic acid, 37-41% oleic acid and 37-41% linoleic acid. More recently, interest in rice oil escalated with its identification as a healthy oil that reduces serum cholesterol. Rice bran is a good source of antioxidants including vitamin E and oryzanol (ferulic esters of sterols and triterpene alcohols), cholesterol-lowering waxes and antitumor compounds like rice bran saccharide.Besides applications in nutrition and in phyto-chemicals, rice bran oil has traditionally been used for industrial applications, such as dimer acid manufacturing, depending on pricing for alternative vegetable oils. 

There are other examples of the calculation of phase equilibrium that are of practical interest and worthy of further discussion. For example, Rodrigues et al studied the phase equihbrium for (rice bran oil + fatty acid-s + ethanol + water + y-oryzanol + tocols). y-oryzanol is a mixture of several ferulic acid [(E)-3-(4-hydroxy-3-methoxy-phenyl)prop-2-enoic acid] esters of sterol and triterpene alcohols. Tocols consist of tocopherols and tocotrienols. y-oryzanol. Tocols are minor components of rice bran oil possessing antioxidant and other beneficial physiological properties. Rodrigues et al applied the pseudo-component method with the NRTL and the UNIQUAC model to calculate the LLE of this compositionally very complex system. For parameter estimation model fatty systems were investigated. 

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