glycoside


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Related to glycoside: tannin, Cyanogenic glycoside

Glycoside

A large important class of sugar derivatives in which the sugar is combined with a nonsugar. In their cyclic forms, monosaccharides (simple sugars) possess one carbon (C) atom (the anomeric carbon) that is bonded to two oxygen (O) atoms; one oxygen atom forms a part of the ring, whereas the other is outside the ring (exocyclic) and is part of a hydroxyl (OH) group. If the oxygen atom of the anomeric hydroxyl group becomes bonded to a carbon atom, other than that of a carbonyl (C ═ O) group, the resulting compound is a glycoside. A glycoside thus consists of two parts (see illustration): the sugar (glycosyl) unit, which provides the anomeric carbon, and the moiety (the aglycon), which is the source of the exocyclic oxygen and carbon atoms of the glycosidic linkage. Such compounds frequently are referred to as O-glycosides to distinguish them from analogs having a sulfur (thio- or S-glycosides), nitrogen (amino- or N-glycosides), or carbon (anomalously called C-glycosides) as the exocyclic atom on the anomeric carbon. See Monosaccharide

The formation of glycosides is the principal manner in which monosaccharides are incorporated into more complex molecules. For example, lactose (illus. b), the most abundant disaccharide in mammalian milk, has a glycosidic bond involving the anomeric carbon of d -galactose and the C-4 hydroxyl of d -glucose. The anomeric carbon atom can exist in either of two stereoisomeric configurations, a fact which is of immense importance to the chemistry and biochemistry of glycosides. For example, the principal structural difference between cellulose and amylose is that cellulose is β-glycosidically linked whereas amylose is α-linked. Humans are able to digest amylose but are unable to utilize cellulose for food. See Cellulose, Lactose

Structural formulas of two glycosidesenlarge picture
Structural formulas of two glycosides

A very large number of glycosides exist in nature, many of which possess important biological functions. In many of these biologically important compounds the carbohydrate portion is essential for cell recognition, the terminal sugar units being able to interact with specific receptor sites on the cell surface.

One class of naturally occurring glycosides is called the cardiac glycosides because they exhibit the ability to strengthen the contraction of heart muscles. These cardiotonic agents are found in both plants and animals and contain complex aglycons, which are responsible for most of the drug action; however, the glycoside may modify the biological activity. The best-known cardiac glycosides come from digitalis and include the drug digoxin.

Glycosidic units frequently are found in antibiotics. For example, the important drug erythromycin A possesses two glycosidically linked sugar units. See Antibiotic

Perhaps the most ubiquitous group of glycosides in nature is the glycoproteins; in many of them carbohydrates are linked to a protein by O-glycosidic bonds. These glycoproteins include many enzymes, hormones, such antiviral compounds as interleukin-2, and the so-called antifreeze glycoproteins found in the sera of fish from very cold marine environments. See Amino acids, Carbohydrate, Enzyme, Glycoprotein, Hormone

Glycolipids are a very large class of natural glycosides having a lipid aglycon. These complex glycosides are present in the cell membranes of microbes, plants, and animals. See Glycolipid, Lipid

glycoside

[′glī·kə‚sīd]
(biochemistry)
A compound that yields on hydrolysis a sugar (glucose, galactose) and an aglycon; many of the glycosides are therapeutically valuable.
References in periodicals archive ?
The present work reports for the first time the characterization of seven flavonoid glycosides, 1-7, from all parts of H.
This process promotes enzymatic degradation of cyanogenic glycosides. If the soaking or drying time is too short, enzymatic degradation will be inadequate, and cyanogenic glycosides remain high (5).
The partnership leverages the two companies' complementary strengths for bringing to market fermentation-derived Reb M and Reb D steviol glycosides. DSM brings its biotechnology know-how, providing R&D expertise, including strain development and fermentation process development capabilities, as well as customer relationships in specific market segments.
However, the use of decreasing concentrations (100, 75, 50 or 25%) of vitamin [D.sub.3], that is, the reduction of up to 75% of the inclusion of vitamin [D.sub.3] in the premix plus the 1,25[(OH).sub.2][D.sub.3] glycoside supplementation, did not alter any of bone quality variables of the broilers that were evaluated in the present study.
With 10 compounds, the Lippia umbelata phenolic pattern was also complex, formed by one chrysoeriol glycoside (45), one apigenin glycoside (44), five luteolin-7-O-glycosides (8, 9, 13, 18 and 19), and three phenolic acids (2, 15 and 21) (Table 3 and Figure 1).
For instance, diCQA positional isomers, apart from being isobaric constituents of each other, also produce similar fragmentation patterns to structurally related molecules such as caffeoylquinic acid (CQA) glycosides [12-14], making identification in different plant species very challenging.
However, research revealed that Reb A is just one of the 40+ steviol glycosides in the stevia leaf.
According to this method, endo-glucanase III which cannot be detected by the conventional method of using p-nitrophenyl glycoside could be detected with higher sensitivity by using glycosyl fluoride substrates (Fluoride ion-detecting enzyme screening (FIDES)).
Therefore, the present study was undertaken to optimize the cyanogenic glycoside content of both the succulent and fermented bamboo shoot and to analyze their nutritional parameters.
Triterpene glycosides belong to a large group of compounds of glycoside nature with historically established name "saponins" (from the Latin "sapo," soap) [31].
Given the membership of the two receptors to the same family and the signal proceeding through a common downstream pathway, we did not discriminate between either of receptor engagement upon insulin or steviol glycoside stimulation.
These results demonstrate that SM extract is absorbed and rapidly enters the circulatory system as apigenin, which is the aglycone of flavone glycosides. However, flavone glycosides were not detected in the plasma during 4 h after the administration.