Uridine

Uridine is a nucleoside formed by the attachment of the pyrimidine base uracil to one molecule of ribose via a β-N1-glycosidic bond. Its chemical formula is C9H12N2O6 and its molecular weight is about 244.2 g/mol. In biology, uridine is a standard component of RNA.

In cells, uridine can be obtained from the diet or synthesized de novo in the pyrimidine biosynthetic pathway. It participates in RNA synthesis as uridine monophosphate (UMP) after phosphorylation. Through subsequent phosphorylation, UMP becomes UDP and then UTP, which are essential for RNA polymerization and also serve as precursors for UDP-sugars used in glycosylation and other biosynthetic processes.

Uridine is maintained in cellular pools through salvage pathways. Uridine kinase catalyzes the formation of UMP from uridine, while various phosphatases and nucleotidases regulate the interconversion between nucleosides and nucleotides. Catabolism ultimately yields uracil and ribose-derived metabolites that are excreted or further metabolized.

Medical relevance includes the use of uridine triacetate as an FDA-approved antidote for overdose or severe toxicity from the chemotherapy agents 5-fluorouracil and capecitabine. As an oral prodrug, it releases uridine after absorption to help mitigate toxic effects.

Dietary sources of uridine include RNA-rich foods, such as meat and yeast-derived products. It is also available as a dietary supplement, sometimes in formulations paired with choline and DHA for potential brain-health applications. Evidence for clinical benefits remains limited and it is not a replacement for established therapies.