Glycosid

Glycosid is a term used in chemistry and biochemistry to denote glycosides, a class of molecules in which a sugar moiety is covalently bound to a non-sugar moiety through a glycosidic linkage. In English-language literature the corresponding term is glycoside, but Glycosid appears in several languages, notably German, where it is used for the same concept.

The glycosidic bond can connect the anomeric carbon of a sugar to an oxygen, nitrogen, or carbon atom of the aglycone, giving O-, N-, or C-glycosides. The sugar portion is called the glycone, while the non-sugar portion is the aglycone or genin. Glycosides may be alpha- or beta-configured depending on the stereochemistry at the anomeric center.

Hydrolysis of glycosides yields the sugar and the aglycone. In nature, hydrolysis is catalyzed by enzymes called glycosidases; acids can also promote cleavage under appropriate conditions. Glycosides serve a wide range of roles, particularly in plants, where they store and transport active compounds and defense chemicals. Many medicines are glycosides, including cardiac glycosides such as digitoxin and digoxin, and various flavonoid or anthraquinone glycosides.

Natural biosynthesis involves glycosyltransferase enzymes that attach sugar units to aglycones. Chemists can prepare glycosides synthetically by glycosylation reactions, enabling production of pharmaceuticals, sweeteners, and analytical standards.