glycoside

A glycoside is a compound in which a sugar moiety, called the glycone, is bound to a non-sugar component, the aglycone, through a glycosidic bond. This bond typically forms by condensation between the anomeric carbon of a sugar and a hydroxyl, amine, or other group on the aglycone. Glycosides are common in plants and other organisms and often serve roles in storage, transport, and defense.

Structure and linkage: The most common type is an O-glycoside, where the sugar attaches via an oxygen atom to the aglycone. N-glycosides and C-glycosides also occur. The anomeric carbon can have alpha or beta configuration, influencing properties and enzymatic processing. The naming of glycosides usually reflects the sugar involved and the aglycone.

Biosynthesis and hydrolysis: Glycosides are formed in biology by glycosyltransferases, which transfer sugar units to acceptor molecules. In metabolism or digestion, glycosidic bonds are cleaved by glycosidases or acidic conditions to yield the sugar component and the aglycone, which may be pharmacologically active, toxic, or biologically functional.

Examples and significance: Plant glycosides include salicin, amygdalin, and cardiac glycosides such as digoxin and ouabain. Many pharmaceuticals are glycosides or are glycosylated to improve solubility, stability, and bioavailability. Glycosides also contribute flavors and aromas in foods. Because hydrolysis can release active or toxic aglycones, glycoside chemistry has important implications for pharmacology, safety, and metabolism.