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 ?
However, research revealed that Reb A is just one of the 40+ steviol glycosides in the stevia leaf.
Cardiac glycosides are chemically similar to digoxin, and are distributed throughout the plant, either fresh or dried (LANGFORD & BOOR, 1996; SOTO-BLANCO et al.
After the monumental work on the establishment of the stereochemical configuration of all aldosugars, Fischer extended his studies to glycoside synthesis.
2013) This allows manufacturers to use compounds that are significantly less expensive than ginkgo leaf extract to achieve the typical 24% flavonol glycoside concentration, (van Beek and Montoro 2009) Rutin, a flavonol glycoside, and aglycones quercetin, kaempferol, and isorhamnetin, are currently the most popular ingredients used to spike products, as they are highly effective in inflating the flavonol glycosides assay values in ginkgo products.
Effects of Malvidin and Its Glycosides on Reactive Oxygen Species in Cells.
Besides these sweet glycosides stevia is also a nutrient rich herb containing substantial amount of other nutrients like 80 to 85 per cent water protein fibre amino acids free sugars iminosugar steviamine lipids essential oils ascorbic acid beta carotene riboflavin thiamine austroinulin nilacin rebaudi oxides gibberellic acid indole-3-acetonitrile apigenin quercetin isoquercitrin luteolin miocene kaempferol stigmasterol xanthophyllus umbeliferone chlorogenic acid caffeic acid dicaffeoylquinic acid chromium cobalt magnesium iron potassium phosphorus and trace elements.
No synonymous SNPs in the rrs gene result in reduced amino glycoside binding while allowing for preserved ribosome function.
At present, there is a very few data on stevioside mechanism of action, but experiments with animals have shown that this glycoside is a calcium channel blocking agent [16].
Following cold soak, total glycoside concentration was greater in the pigeage than delestage tanks by an average of 49% (Table V).
Cargill VP and Global Business Director for Health Ingredients David Henstrom remarked, "We are very excited about and fully committed to supporting fermentation-based steviol glycoside technology to provide our customers with a wider array of great-tasting options.
may mimic cardiac glycoside poisoning on initial presentation with bradycardia, heart blocks, and ventricular tachydysrhythmias sodium channel activator poisonings are often accompanied by hypotension and cardiovascular collapse; are refractory to reversal with digoxin-specific Fab; and may require inotropic support, temporary cardiac pacing, or temporary cardiopulmonary bypass.
The sweetest and best-known steviol glycoside is Rebaudioside-A (Reb-A), which is to 400 times sweeter than sugar.