Phytosterols functions

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. 

Wqsowicz, E. (2002). Cholesterol and phytosterols, in Sikorski, Z.E. and Kolakowska, A., eds.. Chemical and Functional Properties of Food Lipids, CRC Press, Boca Raton, 93-107. 

Hicks, K.B. and Moreau, R.A. 2001. Phytosterols and phytostanols Functional food cholesterol busters. Food Technol. 55, 63-67. 

Phytosterols are structurally very similar to cholesterol and the major phytosterols (campesterol, sitosterol and stigmasterol) have the same kind of membrane viscosity modulating function in plants that cholesterol (C27 3-OH-C6 C6 G61 C5—C8) has in animals. Campesterol (24-methylcholesterol), sitosterol (24-ethylcholesterol) and stigmasterol (A22, 24-ethylcholesterol) are widespread phytosterols. The animal sterols lanosterol and cholesterol are present in particular plants. Phytosterol esters reduce cholesterol absorption and lower LDL-cholesterol. 

The range of food components now considered as bioactives include vitamins, minerals, functional lipids, probiotics, amino acids, peptides and proteins, phytosterols, phytochemicals and antioxidants (Wildman 2001). Their structure and function vary widely and are important considerations when adding them to food. The health aspects of bioactive ingredients and functional foods are not covered here as they are beyond the scope of this chapter. 

The demand for healthy foods has led to the development of several entirely new healthy ingredient and additive categories (Heasman and Mellentin 2001 Sloan 2004). An entirely new sector of functional food ingredients has developed, including products such as omega-3 fatty acids and phytosterols for cardiovascular health, prebiotics and probiotics for gut health, antioxidants, polyphenols and phytochemicals, and bioactive peptides. The established vitamins and minerals sector has also benefited from this functional food trend, with more and more products being fortified with beneficial vitamins and minerals. 

Jones, P.J.H. AbuMweis, S.S. 2009. Phytosterols as functional food ingredients linkages to cardiovascular disease and cancer. Curr. Opin. Clin. Nutr. Metab. Care 12 147-151. 

Piironen, V. Lampi, A.-M. 2004. Oeeurrenee and levels of phytosterols in foods. In Phytosterols as Functional Food Components and Nutraeeutieals (Dutta, P.C., Ed.) CRC Press, Marcel Dekker Ine., New York, pp. 1-27. 

Recent developments in the area of oils and fats has led to the production of specialty lipids from novel sources such as fruit seeds, nuts, and other minor plant sources. In addition, preparation of structured lipids for a myriad of applications has been of interest. Minor components of oils and fats may be isolated during processing and used as nutraceutical and functional food ingredients. Examples are lecithin, phytosterols, tocopherols, and tocotrienols, among others. Obviously, the health-promoting potential of such products is also of interest. 

P. C. Dutta, Phytosterols as Functional Food Components and Nutraceuticals, Marcel Dekker, New York, 2004. 

Soybean tocopherols are the major source of natural fat-soluble antioxidants and Vitamin E. The Vitamin E activity of natural d-cx-tocopherol is much greater that that of synthetic Vitamin E, which is a mixture of eight stereoisomers (203). Phytosterols are used as raw materials for over 75% of the world s steroid production. The more recent application of phytosterol, phytostanol, and their fatty acid esters in margarine and table spreads is based on the blood cholesterol-lowering effect of these compounds (204,205). The recent development of functional foods containing phytosterols has been reviewed by Hollingsworth (206) and Hicks and Moreau (207). 

Squalene and phytosterols are components present in the unsaponifiable lipid fraction of foods (as tocopherols). Squalene is an intermediary in cholesterol biosynthesis, and 33.9-58.4 mg/100 g of it was found in the lipid fraction of quinoa (Jahaniaval et al., 2000 Ryan et ah, 2007) squalene is the biochemical precursor of the whole family of steroids, and besides their effective antioxidant activity, tocotrienols have other important functions, in particular in maintaining a healthy cardiovascular system and a possible role in protection against cancer (Nesaretnam, 2008). Squalene is used as a bactericide and as an intermediate in many pharmaceuticals, organic coloring materials, rubber chemicals, and surface-active agents (Ahamed et ah, 1998). 

Brassinosteroids are grouped into C, Cg, and steroids like the typical phytosterols. These classifications result basically from different alkyl substitutions in the side chain, that is no substituent in steroids (14, 15 ), a methyl (1, 3,5, 7-9, 16-22,29) or an exomethylene ( 2,4, 6) at C24 in steroids, and an ethyl at C24 (12 )or an ethylidene at C24 ( 10,11, 13) or an exomethylene at C24 with a methyl at C25 ( 23-28 ) in steroids. The structure-activity relationship reveals that alkylation in the side chain is necessary for biological activity. More especially, the presence of a saturated alkyl ( a methyl or an ethyl ) at C24 and a methyl at C25 makes brassinosteroids biologically more active. Thus, 25-methylbrassinolide bearing both 24-methyl and 25-methyl functions has been chemically synthesized and it is more potent than brassinolide which, until now, had been considered to be the most potent brassinosteroid (44). 

---