Phytosterols

Stabilized whole rice bran is rich in protein, lipids, dietary fiber, vitamins, essential minerals, and important nutraceuticals such as phospholipids, choline, inositol, phytosterols, tocols, and tocotrienols. Tocols and tocotrienols are potent antioxidants that reduce the risk of cancers and CVD. The whole rice bran is stabUized in order to denature lipases that cause oxidative rancidity and to protect the intrinsic nutraceutical compounds. The stabilization of the rice bran is usually done by applying heat in an extrnder. The preservation of the oryzanol is of utmost importance because this compound is very effective in promoting cardiovascular health (Hoffpauer 2005). 

There has been much interest in the health benefits of consuming phytosterols, especially since the FDA issued a health claim for their use. These phytochemicals inhibit the absorption of cholesterol from the small intestine, thus effectively lowering total blood cholesterol, and LDL. An amount of only 1 to 3 g per day reduces cholesterol by 5% to 20%. A typical dietary intake of phytosterols varies from 200 to 400 mg per day (White and Weber 2003). The main sterol present in the whole oat kernel and extracted oil is P-sitosterol, followed by campesterol, and stigmasterol. The second dominant sterol in oats is avenasterol (Chung and Ohm 2000). 

Sorghum grain contains 39.4 mg/100 g of 4-demethysterols mainly present as free forms. Approximately 75% of these compounds were associated with the germ. Mahadevappa and Raina (1978) reported the total sterol lipid content as 149 mg/100 g in finger millet. The major sterol was P-sitosterol, which comprised 80%-84% of the total sterols. 

Research on maize fiber (Moreau et al. 1996) has shown that oil associated with the fiber fraction is different in composition compared to regular oil obtained from the germ. The fiber oil contains important amounts of ferulate phytosterol esters, free phytosterols, and fatty acid phytosterol esters, which lower serum cholesterol in laboratory animals. The most common class is ferulate phytosterol esters dominated by sitostanol, which is considered more efficient in lowering cholesterol. Phytosterols, such as ergosterol, campesterol, P-sitosterol, and stigmasterol, compete for cholesterol absorption, and therefore are considered hypocholesterolemic and preventive against CVD. According to Raicht et al. (1980) and Fiala et al. (1985) the supplementation of 0.2% P-sitosterol decreases the occurrence of chemically induced colon tumors. 

Sterols such as stigmasterol and sitosterol are essential components of cell membranes, and they are also used as the starting material in the production of steroidal drugs. Phytosterols are characterised by a hydroxyl group attached at C-3 and an extra methyl or ethyl substituent in the side chain not present in animal sterols (Harborne and Baxter 1993). 

Phytosterols are minor but beneficial components of the human diet since they may inhibit growth of tumours and help in regulation of blood cholesterol. Therapeutically they are important constituents of the following herbs. 

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In the initial black Hquor concentration, saponified fatty and resin acid salts separate as tall oil soaps (see Tall oil). These soaps can be skimmed from the aqueous spent Hquor, acidified, and refined to give a cmde tall oil composed of resin acids, chiefly abietic and neoabietic fatty acids, chiefly oleic and Hnoleic and an unsaponifiable fraction made of phytosterols, alcohols, and hydrocarbons. Tall oil is fractionated primarily into fatty acids (see... 

The 22-aldehyde is the only aldehyde considered in this review on account of its importance as an intermediate in the conversion of phytosterols to preg-nan-20-ones. 

Tenerife and La Palma, revealed the existence of luteolin and an array of simple phenolic derivatives as well as three known phytosterols, B-amyrin, sitosterol, and stigmasterol. The phenols identified comprised a set of phenylpropanoids myristicin [566] (see Fig. 6.16 for structures 566-573), methyleugenol [567], todadiol [568], todatriol [569], crocatone [570], elemicin [571], apiole [572], and the coumarin scopoletin [573]. The occurrence of these compounds is recorded in Table 6.5. The differences between the two profiles were taken by Gonzalez and his co-workers... 

Table 6.5 Distribution of simple phenols and phytosterols in Todaroa aurea (from Gonzalez etal., 1988)...

Other compounds include the plant-derived sterols (phytosterols) and other sulphur-containing compounds found in onions and their relatives. Only a few of the more important examples will be discussed in the following sections. 

LING w H, JONES p J (1995) Dietary phytosterols a review of metabolism, benefits and side effects. Life Sci. 57 195-206. 

Phytosterols have been demonstrated as being anti-cancer components in the diet (Awad and Fink 2000). Scientific studies indicate that phytosterols may offer profection against colon, breast and prostate cancers (Vanderhaeghe and Bouic, 2000). The possible mechanisms, as reported by these authors, include the effect of phytosterols on membrane structure and function and on the signal transduction pathways that regulate tumor growth and apoptosis. The rice bran derived phytosterol-cycloartenol-ferulic acid ester on the central nervous system has been studied by Hiraga et al. (1993). 

Natural products have been noted for their potential health benefits from time immemorial and are the basis of Ayurveda, an ancient Indian medical practice (Bushkin and Bushkin, 2002). However, the potential benefits of several natural products reside in one or two active ingredients. For example green tea stands for polyphenols, soy for soy estrogens, broccoli for isothiocyanates and grape seed for polyphenols. The beauty of rice bran is that there are more than 100 antioxidants, several categories of bioactive phytonutrients, such as IP6, polyphenols, phytosterols, tocotrienols, y-oryzanol, B vitamins, minerals and trace minerals in addition to fat, protein, fiber, polysaccharides and other nutrients. These phytonutrients and antioxidants of rice bran are believed to act at the cellular level, and their synergestic function is responsible for the positive health benefits. 

AWAD A B, FINK 0 s (2000) Phytosterols as anticancer dietary components Evidence and mechanism of action. J Nutr, 130 (9) 2127-30. 

Fahy, D.M., O Callaghan, Y.C., and O Brien, N.M., Phytosterols lack of cytotoxicity but interference with 3-carotene uptake in Caco-2 cells in culture, FoodAddit. Con-tarn., 21, 42, 2004. 

Borel, R, Factors affecting intestinal absorption of highly lipophilic food microconstituents (fat-soluble vitamins, carotenoids and phytosterols), Clin. Chem. Lab. Med., 41, 979, 2003. 

Consumption of food with sterols and their oxides is a health concern. Oxidation products of phytosterol, including epimers of 7-ketositosterol and 7-hydroxycampes-terol, 7-ketocampesterol, epimers of 5,6-epoxy-sitosterol, 5,6-epoxycamposterol, 24 a-ethylcholestane-3(3,5,6 (3-triol, and 24 a-methylcholestane-3(3,5,6 (3-triol, in deep-fried potato chips in palm oil, sunflower oil, and high oleic sunflower oil were quanhtahvely analyzed by PTLC followed by GC and GC-MS [73]. 

Ezetimibe is the first drug in a new class of agents referred to as cholesterol absorption inhibitors. Ezetimibe blocks biliary and dietary cholesterol as well as phytosterol (plant sterol)... 

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