Glikozyd

Glikozyd, in English glycoside, is a molecule in which a sugar moiety (glycone) is bound to a non-sugar aglycone via a glycosidic bond. The bond is most commonly O-glycosidic, but C-glycosides also occur. The sugar part can be glucose, galactose, rhamnose, arabinose and other monosaccharides, while the aglycone spans a wide range of structures, including phenolics, terpenoids, steroids and alkaloids.

Glikozydy occur widely in nature, especially in plants, where they serve roles in storage, defense and signaling. They are a major class of secondary metabolites and can influence solubility, stability and bioactivity. Many glycosides are metabolized by glycosidases that hydrolyze the glycosidic bond to release sugar and the active aglycone.

Examples encompass cardiac glycosides such as digitoxin and digoxin from Digitalis species, which inhibit Na+/K+-ATPase and affect heart contractility; anthraquinone glycosides; cyanogenic glycosides such as amygdalin; saponins; flavonoid glycosides; and salicin, a glucoside from willow used historically as a precursor to salicylic acid.

Biosynthesis typically involves glycosyltransferases that attach sugar units to the aglycone. In metabolism, glycosides can be activated or deactivated by hydrolysis, depending on context. Analytical study often starts with hydrolysis to identify the aglycone and sugar components, followed by chromatographic and spectrometric techniques.

Pharmacological and safety aspects vary widely; cardiac glycosides have potent effects and narrow therapeutic windows, necessitating careful consideration of dosage and interactions.