Ribosides

Ribosides are a class of glycosides in which the sugar component is ribose. In biochemistry, the term is frequently used to refer to ribonucleosides, compounds in which a ribose sugar is linked to a nitrogenous base (a purine or pyrimidine) by a beta-N-glycosidic bond. Common ribonucleosides include adenosine, guanosine, cytidine, uridine, and inosine. The deoxyribose counterparts are called deoxyribonucleosides, with thymidine being a well-known example.

Structure and nomenclature

Ribose in these molecules typically adopts the beta-D-ribofuranose form, and the glycosidic bond forms at the anomeric carbon (C1′) of the sugar. Nucleosides are the building blocks of nucleotides, which carry phosphate groups and participate in a wide range of cellular processes. Names of nucleosides end in -osine (adenosine, guanosine, cytidine, uridine, inosine); thymidine is the corresponding deoxyribonucleoside.

Biological relevance

Ribonucleosides occur naturally as components of RNA and participate in signaling and metabolism. They also serve as precursors in salvage pathways that recycle bases into nucleotides. In pharmacology, many ribonucleoside analogs have therapeutic uses as antiviral or anticancer agents, reflecting the central role of nucleoside chemistry in biology. A notable modern example is nicotinamide riboside, a riboside that acts as a precursor to the coenzyme NAD+.

Summary

Ribosides chiefly denote ribonucleosides, structures formed by a ribose sugar linked to a nitrogenous base. They are fundamental to nucleic acid biology and have broad relevance in medicine through nucleoside analogs and NAD+ metabolism.