Glycoside naturally occurring

Several other naturally occurring antioxidants have been identified in oils. Sesamol [533-31-3] (6) occurs as sesamoline [526-07-8], a glycoside, in sesame seed oil. FemUc acid [1135-24-6] (7) is found esterified to cycloartenol [469-38-5] in rice bran oil and to 3-sitosterol in com oil. Although it does not occur in oils, rosemary extract has also been found to contain powerful phenoHc antioxidants (12). 

Manufacture. The hydrolysis of the naturally occurring P-glycoside (saUcin) (8) with hydrochloric or sulfuric acid affords saligenin (9) and glucose (10) (eq. 11). 

Stevioside and rebaudioside A are diterpene glycosides. The sweetness is tainted with a bitter and undesirable aftertaste. The time—intensity profile is characteristic of naturally occurring sweeteners slow onset but lingering. The aglycone moiety, steviol [471 -80-7] (10), which is the principal metaboHte, has been reported to be mutagenic (79). Wide use of stevia ia Japan for over 20 years did not produce any known deleterious side effects. However, because no food additive petition has been presented to the FDA, stevioside and related materials caimot be used ia the United States. An import alert against stevia was issued by the FDA ia 1991. In 1995, however, the FDA revised this import alert to allow the importation and use of stevia as a diet supplement (80), but not as a sweetener or an ingredient for foods. Several comprehensive reviews of stevia are available (81,82). 

By far the majority of carbohydrate material in nature occurs in the form of polysaccharides. By our definition, polysaccharides include not only those substances composed only of glycosidically linked sugar residues but also molecules that contain polymeric saccharide structures linked via covalent bonds to amino acids, peptides, proteins, lipids, and other structures. 

Assay results with the two new 1,2-cis (ft-d) cardenolides show enhanced activity as compared with the two unnatural, a-D-rhamnosides. They have potencies that fall well within the range for those of the naturally occurring cardenolides. These results support the postulate that the a-D-glycosidic linkage in cardenolides containing D-sugars is unfavorable for cardiotonic activity. 

Naturally occurring compounds called cyanogenic glycosides, such as lotau-stralin, release hydrogen cyanide, HCN, when treated with aqueous acid. The reaction occurs by hydrolysis of the acetal linkage to form a cyanohydrin, which then expels HCN and gives a carbonyl compound-fa) Show the mechanism of the acetal hydrolysis and the structure of the cyanohydrin that results. 

Particularly in naturally occurring glycosides, the compound ROH from which the carbohydrate residue has been removed is often termed the aglycone, and the carbohydrate residue itself is sometimes referred to as the glycone . 

Of this class of naturally occurring, sweet compounds, the flavanone glycosides found in citrus fruits have achieved considerable interest, owing to the systematic studies of Horowitz and Gentili " (see Fig. 20). 

It is known that the naturally occurring dihydrochalcone glycosides phloridzin (75) and glycyphillin (76), which are 2-yl glycosides, possess little or no sweetness, whereas phyllodulcin (77), which is not a glycoside, has the same taste properties as the dihydrochalcones it is 400 times sweeter than sucrose. ... 

The structure-sweetness relationships of other naturally occurring, sweet glycosides have received very little attention. In most cases, virtually no systematic, structural modifications have been reported. 

Glycosides are the predominant forms. Although in humans flavonoids have been shown to be absorbed in their naturally occurring glycosidic forms (Hollman and Katan, 1998), isoflavones are not. It is generally accepted that to be adsorbed by enterocytes across the intestinal wall, isoflavone glycosides... 

These contain C-NO2 bonds in contrast to the nitrate esters of, for example, glycerol and pentae-rythritol with O-NO2 bonds. Nitroalkanes have been used as solvents, and there are a few naturally occurring nitroalkanes such as the glycoside of the toxic 3-nitropropionic acid and the 0-methyl... 

Lechtenberg, M. and Nahrstedt, A. (1999) Cyanogenic glycosides, in Naturally Occurring Glycosides (ed. R. Ikan) John Wiley Sons, Ltd, Chichester, UK, pp. 147-191. 

HALKIER, B.A., Glucosinolates. In Naturally occurring Glycosides (R. Ikan, ed.), John Wiley Sons, London. 1999, pp. 193-223. 

Scheme 18.14 Naturally occurring glycosides ofthe grasshopper ketone-...

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