Oligosaccharides, sources

Oligosaccharides also occur widely as components (via glycosidic bonds) of antibiotics derived from various sources. Figure 7.20 shows the structures of a few representative carbohydrate-containing antibiotics. Some of these antibiotics also show antitumor activity. One of the most important of this type is bleomycin A2, which is used clinically against certain tumors. 

The enzymes are available from a variety of sources and are often specific for certain types of glycosidic linkages and also for their anomeric natures. The sites of action of endoglycosidases F and H are shown in Figure 47-5. F acts on both high-mannose and complex oligosaccharides, whereas FI acts on the former. 

Rice bran fiber has fructo-oligosaccharides - a pre-biotic that helps friendly bacteria to proliferate in the gastrointestinal environment and improves intestinal and colon health (Tomlin and Read, 1988). Recent studies in humans (Kahlon and Chow, 1997) have revealed that rice bran fiber not only normalizes bowel function, but also helps in conditions such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) and Crohn s disease, and lowers the lipid levels. Rice bran fiber has been shown to significantly reduce renal stones (Jahnen et al., 1992). It is a good source of fiber in weight loss programs and therapeutic fiber diets for diabetics and heart patients. Fiber diets prevent cancer of the colon and large bowel, control obesity and improve bowel function. 

Low, N. H., Brisbane, T., Bigam, G., and Spoms, P. (1988). Carbohydrate analysis of western Canadian honeys and their nectar sources to determine the origin of honey oligosaccharides. /. Agric. Food Chem. 36, 953-957. 

Caryophyllidae are an interesting source of oligosaccharides and peptides with potential anti-inflammatory and/or immunomodulating effect. These polar compounds might for instance explain the fact that the fresh juice expressed from Aerva lanata (L.) Juss. (Amaranthaceae) inhibits carrageenan-induced edema in rodent. Note that the seeds of Gomphrena species inhibit the formation of IL-6 by osteoblastic cells (MC3T3-E10) without cytotoxicity in vitro. Such property could be useful for the treatment of chronic rheumatoid arthritis, infection, and cancer. In the Lauraceae, trans-cinnamal-dehyde from Cinnamomum cassia (Lauraceae, order Laurales) inhibits in vitro the... 

Silicon presents an attractive option among eledrophilic activating and dehydrating agents of hemiacetals because of the wide commercial availability of eledrophilic silicon sources. The two main classes of silicon electrophiles used, namely silyl halides and silyl sulfonates, have been demonstrated to promote a variety of glycosylations including some examples of oligosaccharide synthesis. 

Oligosaccharides and glycoconjugates in living cells often exist as closely related mixtures. Their isolation from natural sources in homogeneous form is therefore very difficult, involving tedious purification and difficult characterization. This sequence of steps tends to result in low yields. This difficult situation presents chemical synthesis with a major opportunity to positively affect progress in the biochemical understanding of the processes described above.4... 

Einally, another group of oligosaccharides that have attracted attention for their potential anti-adhesive activity are the mannooligosacchar-ides (MOS). The MOS can be extracted from natural sources, produced... 

Guggenbichler, J. P., De Bettignies-Dunz, A., Meissner, P., Schellmoser, S., and Jurenitsch, J. (1997). Acidic oligosaccharides from natural sources block adherence of Escherichia coli on uroepithelial cells. Pharm. Pharmacol. Lett. 7, 35-38. 

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