Arabinoside

Arabinoside refers to nucleosides in which the sugar component is arabinofuranose rather than ribofuranose. The arabinose sugar is linked to a nucleobase via a glycosidic bond to form arabinoside nucleosides. The best-known examples are vidarabine (ara-A), cytarabine (ara-C), and arabinoguanosine (ara-G). A defining feature is the configuration of the arabinose moiety, which differs from that of ribose and deoxyribose, notably at the 2' position. This structural difference influences how the molecule is recognized by cellular kinases and DNA polymerases, and many arabinosides require phosphorylation to the triphosphate form to exert biological activity.

Vidarabine (ara-A) was among the early antiviral nucleosides and showed activity against herpes simplex and varicella-zoster viruses, though its use has declined in favor of newer agents. Cytarabine (ara-C) is a widely used chemotherapy agent for hematologic malignancies, including acute myeloid leukemia and certain lymphomas. As a cytidine analog, ara-C is phosphorylated intracellularly to ara-CTP, which inhibits DNA synthesis by interfering with DNA polymerases and chain elongation. The drug can cause myelosuppression and mucositis; resistance can arise from reduced activation by kinases or increased degradation and nucleotide pool alterations.

Arabinosides are studied for antiviral and anticancer applications, with ongoing efforts to improve pharmacokinetic properties and selectivity. The term also encompasses other sugar–nucleobase combinations that include arabinose as the sugar moiety.