Uridine is a glycosylated pyrimidine analog containing uracil attached to a ribose ring via a β-N₁-glycosidic bond. The analog is one of the five standard nucleosides which make up nucleic acids, the others being adenosine, thymidine, cytidine and guanosine. Uridine has molecular formula C9H12N2O6 and an exact monoisotopic mass of 244.0633 Da; common identifiers include CAS 58-96-8. In cells uridine is phosphorylated to uridine monophosphate UMP and further to UDP and UTP, serving both as a direct RNA building block and as the activated sugar donor UDP-glucose and other UDP-sugar species used in glycosylation and polysaccharide biosynthesis. Chemically it displays keto-enol tautomerism of the uracil ring, a UV absorption maximum near 262 nm useful for photometric detection, and sufficient aqueous solubility for common aqueous assays; typical analytical identification employs HPLC-UV, LC-MS and 1H/13C NMR for confirmation. Uridine participates in nucleotide salvage pathways via uridine-cytidine kinase and interfaces with pyrimidine de novo synthesis through interconversion of nucleoside and nucleotide pools.
Typical analytical specifications for high-purity uridine reference or material grade include assay by HPLC >= 98.0% w/w and total related substances generally limited to <= 1.5% area by HPLC; individual related compounds are commonly limited to <= 0.5% area each. Specific related compounds and typical maximum amounts reported in quality specifications are: uracil (deamination product) <= 0.2% w/w, uridine 5'-monophosphate (UMP) <= 0.5% w/w, oxidized or reduced ring derivatives such as dihydrouridine <= 0.2% w/w, ribose or other sugar-derived fragments <= 0.1% w/w and isomeric nucleosides including pseudouridine/others <= 0.5% w/w where applicable. Water content is typically controlled to <= 1.5% w/w, residual solvents are maintained below ICH Q3C limits, and heavy metals are controlled to <= 10 ppm. Identification and quantitation of impurities are normally performed by validated HPLC-UV methods at 260 to 262 nm with orthogonal confirmation by LC-MS and NMR when required.
Uridine is used biologically as an RNA nucleoside and metabolically as the precursor of UMP, UDP and UTP; it supplies uracil residues during transcription and provides activated UDP-sugar cofactors for glycosylation and glycoconjugate biosynthesis. In laboratory and industrial contexts uridine is used as a biochemical reagent for enzymology, nucleotide metabolism studies, cell culture supplementation in specific protocols, and as a standard or intermediate in synthetic chemistry.
Uridine is a nucleoside, composed of the nucleobase uracil linked to a ribose sugar via a β-N₁-glycosidic bond. When phosphorylated at the 5′ position it becomes a nucleotide: UMP is the monophosphate, UDP is the diphosphate and UTP is the triphosphate form.
Dietary sources high in free or bioavailable uridine include certain organ meats such as liver, brewer’s yeast, and some fish and seafood. Uridine is also present in milk and in smaller amounts across a range of vegetables and fungi; contribution from diet varies because nucleosides are subject to rapid metabolism in the gut and liver.
Uridine and cytidine are both pyrimidine nucleosides distinguished by their nucleobases: uridine contains uracil, cytidine contains cytosine. Both have a ribose sugar linked via a β-N₁-glycosidic bond and are substrates in RNA synthesis and nucleotide metabolism, with cytidine able to be deaminated to uridine under certain biochemical conditions.
