6Cglucosides

6-C glucosides, or 6-C-glucosides, are a subclass of C-glycosides in which a glucose residue is linked to a non-sugar aglycone via a carbon–carbon bond formed at the C-6 position of the glucose moiety. This type of linkage is distinct from the more common O-glycosidic bonds that connect glucose through the anomeric C-1. The 6-C attachment often confers greater chemical stability, including resistance to acid hydrolysis and to many enzymatic cleavages that target O-glycosides.

Natural occurrence and examples: 6-C-glucosides are found in plants, particularly among flavonoids. Notable examples include isovitexin, the apigenin-6-C-glucoside, and isoorientin, the luteolin-6-C-glucoside. The name reflects the site of attachment on the glucose moiety and the identity of the aglycone.

Biogenesis and enzymes: The formation of 6-C-glucosides involves specialized C-glycosyltransferases that transfer glucose from UDP-glucose to the aglycone while forming a C–C bond at the glucose C-6. This enzymatic pathway differs from the transfer processes that yield O-glycosides and contributes to the diversity of plant secondary metabolites.

Structure and analysis: In these compounds, the sugar remains in a stable ring form, and the linkage to the aglycone is a C–C bond at glucose C-6. They are typically characterized by spectroscopic methods such as NMR and mass spectrometry and by chromatographic techniques that separate them from O-glycosides.

Significance: 6-C-glucosides contribute to plant defense, pigment formation, and UV protection. They may influence the pharmacokinetics and bioactivity of plant-derived compounds, depending on stability and metabolism in biological systems. See also C-glycosides, isovitexin, isoorientin, and C-glycosyltransferases.