Heteroglycoside

Heteroglycoside is a glycoside in which the sugar portion, or glycone, contains more than one type of monosaccharide. The term contrasts with homoglycosides, where the sugar residues are all the same. In heteroglycosides, the aglycone (non-sugar) part is linked to an oligosaccharide chain that may be a disaccharide or longer, with diverse sugar units such as glucose, rhamnose, galactose, or arabinose.

These compounds are common in plants and other organisms as secondary metabolites involved in defense, storage, or transport. The biosynthesis typically involves glycosyltransferases that add different UDP-sugar donors in sequence to the aglycone or to a growing sugar chain, producing specific linkages and orientations that influence function.

Representative examples include rutin, a flavonol glycoside in which quercetin is linked to the disaccharide rutinose (a rhamnose–glucose pair). Many other plant and microbial glycosides exhibit heteroglycoside sugar moieties, including various cardiac and steroidal glycosides, which carry multiple distinct sugars in their glycone chains. The composition and arrangement of the sugar units affect properties such as solubility, stability, and bioavailability, and influence susceptibility to enzymatic hydrolysis by glycosidases in digestion or metabolism.

Analytical characterization typically involves hydrolysis to release the aglycone and constituent sugars, followed by chromatographic and spectroscopic methods to determine sugar identities and linkages. Heteroglycosides are a major class of natural products with significant pharmacological and industrial relevance, contributing to the biological activity and pharmacokinetics of many plant-derived compounds.