CGlykoside

CGlykoside, or C-glycoside, refers to a class of glycosides in which the sugar moiety is attached to an aglycone by a carbon–carbon (C–C) bond rather than the typical oxygen–glycosidic (O–C) linkage. This carbon–carbon linkage confers greater chemical and enzymatic stability, particularly resistance to acid hydrolysis and to many glycosidases. While glucose is the most common sugar in C-glycosides, other monosaccharides can occur, and the attachment can take different positional isomers on the aglycone.

In nature, C-glycosides are found in various plant secondary metabolites, most prominently among flavonoids. Notable examples include orientin (luteolin 8-C-glucoside), isoorientin (luteolin 6-C-glucoside), vitexin (apigenin 8-C-glucoside), and isovitexin (apigenin 6-C-glucoside). Puerarin (daidzein 8-C-glucoside) is another widely cited example. These compounds are typically produced by plants through specialized enzymes known as C-glycosyltransferases, which install the sugar via a C–C bond to specific positions on the flavonoid skeleton.

Properties and significance of C-glycosides include enhanced stability against hydrolysis and altered pharmacokinetic profiles, which can influence their biological activity and potential as drug leads. They are of interest in plant metabolomics and chemotaxonomy as well as in the study of natural product biosynthesis. Analytical methods for C-glycosides often exploit their distinctive fragmentation patterns in mass spectrometry and their UV-visible behavior.

Overall, C-glycosides represent a distinct subset of glycosides with unique bond chemistry, biosynthetic pathways, and implications for stability and bioactivity.