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 ?
No synonymous SNPs in the rrs gene result in reduced amino glycoside binding while allowing for preserved ribosome function.
In the present study, the absorption mechanism of phenylethanoid glycosides was studied using in vitro Caco-2 cell model.
The most common steviol glycosides are stevioside and rebaudioside A, which have between 250 and 400 times the sweetness of sugar.
The only commercially available steviol glycosides available today are derived from stevia plants grown and harvested in an agriculture setting.
In addition, the steviol glycoside flavour profile presents further formulating challenges, such as adjusting the sweetness profile to that of sugar, achieving high levels of sweetness intensity, reducing bitterness in high steviol glycosides concentrations, reducing lingering effects and replacing the sugar bulk in sweetened products.
Interestingly, these events occur at nontoxic (nanomolar) concentrations, well below the concentrations of any reported toxic complications encountered with therapeutic cardiac glycoside doses.
Yet, neither flowers nor pollen need ever be seen if flower buds are picked off before they open - a recommended practice since flowering decreases glycoside concentration in the leaves.
PureCircle's food scientists at its Centers of Category Excellence have spent years working on Matrix Solutions, building upon steviol glycoside research learnings since the company's inception.
Puresse Stevia'100 is the ultimate in steviol glycoside purity.
The difference between the intensity of the colours of the experimental and blank (distilled water and Baljet's reagent) samples gave the absorbance and was proportional to the concentration of the glycoside.
The statement read that stevia sweeteners with a steviol glycoside content of at least 95% were deemed to be safe for use in foods.