Rice bran polysaccharides

The carbohydrates in rice bran are made up of the cell wall components such as polysaccharides, oligosaccharides, hemicelluloses, starch and some sugars. The health benefits of rice bran polysaccharides and hemicelluloses are discussed under phytochemicals of rice bran below. It is lactose-free and gluten-free. The water-soluble non-starchy polysaccharides, oligosaccharides and hemicelluloses are concentrated in the water-soluble fraction of rice... 

Rice bran hemicelluloses reduce thymus atrophy in rats (Takenaka, 1992). Hikino et al. (1988) isolated and purified four glycan fractions from rice bran hemicelluloses and named them as Oryzabrans A, B, C, and D. All these glycans were shown to improve the peripheral utilization of insulin, resulting in significant hypoglycemic activity (Hikino et al., 1988 Hikino and Hayashi, 1989). Several investigations into rice bran polysaccharides and hemicelluloses (Masayoshi et al., 1987) have indicated a strong improvement in the immune... 

SRB contains high-quality protein, oil, dietary fiber, polysaccharides, fat-soluble phytochemicals (plant derived bioactive compounds) and other bran nutrients. Rice bran and germ are the richest natural sources of B complex vitamins as well as E vitamins, polyphenols, several antioxidants and minerals. It is now available in the commercial food ingredient market as a safe and effective functional food and dietary supplement. 

Tocotrienols are another group of phytochemicals of rice bran which have a chemopreventive effect and have been demonstrated to inhibit breast cancer (Nesaremam et al., 1998). The polysaccharides of rice bran contain a-glucan, the anti-tumor effect of which has been demonstrated by its inhibition of gastrointestinal carcinogenesis (Akeshita et al., 1992). Rice bran agglutinin has been shown to induce apoptosis of cancer cells by the mechanism of cell cycle dysregulation (Miyoshi et al., 2001). 

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. 

MORiNAGA T (1985) Studies on an antitumor polysaccharide RBS derived fi om rice bran. 1. Preparation, physico-chemical properties, and biological activities of RBS. Yakugaku Zasshi, 105(2) 188-93. 

While the hemicelluloses obtained from the germ, aleuron, and caryopsis coat cell walls all showed a similar monosaccharide composition, this was not the case for the endosperm tissue. Thus, a major difference in the structure of hemicellulosic polysaccharides exists between the preparations obtained from the endosperm cell walls and those from the cell walls of the other parts of the grain, i.e., rice bran. (Rice bran consists of the caryopsis coat, aleuron layer and germ.) Comparison of the detailed structural features of the hemicellulosic polysaccharides of endosperm and bran cell walls will be discussed in the following sections. 

Figure 3. Structure of hemicellulosic polysaccharides obtained from rice bran, (a) Deduced from the results of methylation analysis described in ref. 13.

Carcinogenesis inhibition. Polysaccharide fraction of the dried seed hulls, administered to rats by gastric intubation, was active vs tumor induction with N-ethyl N-nitro-N nitrosoguanidine h Rice bran, administered orally to male rats at a concentration of 4% of the diet, was active. A 1 1 combination of wheat bran and psyllium, at a total level of 8% dietary fiber, offers the highest protection against colon tumor development . 

Polysaccharides Arabinoxylans MGN-3 (51) Rice bran enzymatically modified with Hyp-homyceles mycelia HIV HIV replication, Syncytia formation, Increase T B cell mitogen response [42]... 

Unlike protein and polysaccharides, lipid and resin are not polymers so they could not form stand-alone films. Edible lipids include waxes and oils for example, paraffin wax, beeswax (BW), candelilla wax, camauba wax, rice bran wax, jojoba oil, triglycerides (milkfat fractions), fatty acids, fatty alcohols, and sucrose fatty acid esters. Resins include shellac and terpene (Krochta, 2002). Due to their hydrophobic nature, lipid-based films and coatings exhibit high water resistance and low surface energy (Han and Gennadios, 2005). Generally, edible lipids have been incorporated into proteins and polysaccharides as emulsion or multilayer composite films to improve moisture barrier. 

Ferulic acid is ubiquitously present in plants, mainly as part of the cell walls esterified to polysaccharides such as arabinoxylans. It is also an intermediate in the secondary metabolism of phenylalanine and tyrosine. It can be conveniently isolated from corn hulls, rice bran, and sugar beet. Biocatalytic processes using cinnamoyl esterases and glycosyl hydrolases have been developed for this purpose [32]. Another potentially interesting source is lignin, since ferulic acid is one of the prominent byproducts of its degradation. 

This compound is one of the more important furan derivatives, and is commercially available from pentosans (polysaccharides) which are present in rice husks, oats and corn residues (furfur is the Latin name for bran ). When treated with sulfuric acid, pentosans decompose into pentoses, which then undergo dehydration to the aldehyde (Scheme 6.31). 

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