8Cglucoside

8Cglucoside, or 8-C-glucoside, refers to a type of C-glycoside in which a glucose unit is linked to an aglycone through a carbon–carbon bond at the eighth position of the aglycone (an 8-C glycosidic bond). This contrasts with the more common O-glycosidic linkage found in many glycosides. In plant flavonoids, 8-C-glucosides are exemplified by vitexin (apigenin-8-C-glucoside) and orientin (luteolin-8-C-glucoside).

Chemically, the defining feature is the C–C bond between glucose and the aglycone, which renders the glycoside more resistant to hydrolysis by acids and human intestinal glycosidases than O-glycosides. This greater stability affects its behavior in digestion and may influence bioavailability. 8Cglucosides are formed in plants by specialized C-glycosyltransferases that transfer glucose from UDP-glucose to specific carbon positions on the aglycone.

Occurrence and significance in biology vary, but 8-C-glucosides are commonly found among flavonoids and other phenolics in a range of plant species. They are studied for potential antioxidant activity and contributions to plant defense. In humans, intact C-glycosides are less readily hydrolyzed, so their absorption can differ from O-glycosides; deglycosylation by gut microbiota can also play a role in their metabolism.

Representative examples include vitexin (apigenin-8-C-glucoside) and orientin (luteolin-8-C-glucoside).