glycosidic

Glycosidic describes anything pertaining to glycosides or to glycosidic bonds, covalent linkages between a sugar molecule and another functional group. In carbohydrate chemistry, the glycosidic bond is usually formed at the anomeric carbon (C1) of a sugar. When the linkage involves oxygen, the bond is called an O-glycosidic bond; when it involves nitrogen, it is an N-glycosidic bond; and in rare cases a C-glycosidic bond may form directly to a carbon atom of the aglycone or another sugar.

Glycosides are compounds in which a sugar is bound to a non-sugar moiety (the aglycone) via a glycosidic bond. Examples include disaccharides such as maltose, lactose, and sucrose, which are defined by specific glycosidic linkages (for example, maltose has an alpha-1,4 linkage). Nucleosides such as adenosine and guanosine feature N-glycosidic bonds connecting a purine base to a ribose or deoxyribose sugar (N9 for purines, N1 for pyrimidines).

Biosynthesis and breakdown of glycosides are mediated by enzymes: glycosyltransferases form glycosidic bonds, while glycosidases hydrolyze them. In digestion, disaccharidases cleave dietary disaccharides into monosaccharides. Glycosidic bonds are also central to energy storage molecules like starch and glycogen and to structural polysaccharides like cellulose in plants.

Glycosides have broad biological and pharmacological significance. The sugar moiety influences solubility, stability, and bioavailability, and glycosidic bonds are exploited in drug design and natural product chemistry; many plant secondary metabolites and therapeutics are glycosides (for example digoxin).