glycoside
enUKgly·co·side
G0163200 (glī′kə-sīd′)glycoside
(ˈɡlaɪkəʊˌsaɪd)gly•co•side
(ˈglaɪ kəˌsaɪd)n.
| Noun | 1. | glycoside - a group of compounds derived from monosaccharides |
n.
glycoside
enUKGlycoside
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
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]glycoside
enUKglycoside
[gli´ko-sīd]gly·co·side
(glī'kō-sīd),glycoside
(glī′kə-sīd′)glycoside
BiochemistryA molecule formed from the condensation of either a furanose or a pyranose with another molecule as an acetal nitrogen glycoside or phosphate ester glycoside; cardiac glycosides include digitoxin, digoxin and ouabain.
Herbal medicine
Any of a number of medicinally active compounds produced by plants, which include hydrocyanic (prussic acid), which gives cough syrup its bitter almond flavour, digitoxin, a cardioactive agent, and salicin, the basis for salicylic acid.
glycoside
Pharmacology A molecule formed from the condensation of either a furanose or a pyranose with another molecule as an acetal, nitrogen glycoside, or phosphate ester glycoside; cardiac glycosides include digitoxin, digoxin, ouabaingly·co·side
(glī'kō-sīd)glycoside
an acetal derivative of a sugar that, on hydrolysis by enzymes or acids, gives rise to a sugar. Glycosides containing glucose are called glucosides, those with galactose are called galactosides. They render unwanted substances chemically inert or form food reserves such as GLYCOGEN.Glycoside
gly·co·side
(glī'kō-sīd)glycoside
enUK- noun
Words related to glycoside
noun a group of compounds derived from monosaccharides
Related Words
- organic compound
- glucoside
- nucleoside
- strophanthin
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