purine bases

5-Methyluridine (Thymine riboside) is an endogenous methylated nucleoside found in human fluids; methylated purine bases are present in higher amounts in tumor-bearing patients compared to healthy controls.DNA hypermethylation is a common finding in malignant cells and has been explored as a therapeutic target for hypomethylating agents.

Pyrimidine (Metadiazine)s are heterocyclic, six-membered, nitrogen-containing carbon ring structures, with uracil, cytosine and thymine being the basal structures of ribose-containing nucleosides (uridine, cytidine, and thymidine respectively), or deoxyribose-containing deoxynucleosides, and their corresponding ribonucleotides or deoxyribonucleotides. Pyrimidines serve essential functions in human metabolism as ribonucleotide bases in RNA (uracil and cytosine), and as deoxyribonucleotide bases in DNA (cytosine and thymine), and are linked by phosphodiester bridges to purine nucleotides in double-stranded DNA, in both the nucleus and the mitochondria. Pyrimidine activated sugars are also involved in polysaccharide and phospholipid synthesis, glucuronidation in detoxification processes, glycosylation of proteins and lipids and in the recently identified novel endothelium-derived vasoactive dinucleotides.

Purine (7H-Imidazo(4,5-d)pyrimidine) is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Two of the bases in nucleic acids, adenine and guanine, are purines. Purines from food (or from tissue turnover) are metabolised by several enzymes, including xanthine oxidase, into uric acid. High levels of uric acid can predispose to gout when the acid crystalises in joints; this phenomenon only happens in humans and some animal species (e.g. dogs) that lack an intrinsic uricase enzyme that can further degrade uric acid.

5-Aminoimidazole ribonucleotide (AIR) serves as an intermediate in purine biosynthesis, undergoing enzymatic modifications to form inosine monophosphate (IMP), which is subsequently converted into the purine bases adenine (A) and guanine (G) [1].