Diglycosides

Diglycosides are glycosides in which two monosaccharide units are bound to a non-sugar aglycone (the glycone). The two sugars can be arranged as a single disaccharide moiety attached to the aglycone, or as two separate glycosylations at different hydroxyl groups on the aglycone. The sugars most often encountered are common hexoses and pentoses such as glucose, galactose, rhamnose, xylose, and arabinose, and the glycosidic bonds are typically O-glycosidic, with alpha or beta configurations.

Occurrence and function: Diglycosides occur widely in the plant kingdom and in some microorganisms. They commonly affect solubility, stability, and the biological activity and pharmacokinetics of the aglycone, and may serve in storage or defense.

Biogenesis and metabolism: Glycosyltransferases catalyze the attachment of sugar donors (for example UDP-glucose, UDP-xylose) to specific positions on the aglycone; sequential glycosylation steps can yield diglycosides. Diglycosides can be hydrolyzed by glycosidases to yield the aglycone and the two sugars, either stepwise or simultaneously.

Detection and applications: In natural products chemistry, diglycosides are characterized by chromatographic and spectroscopic methods; hydrolysis and enzymatic assays aid structure elucidation. The glycosylation state influences solubility, polarity, and sometimes bioactivity, making diglycosides important in pharmacology and quality control of botanical materials.