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Guanosine (G), also known as 2-amino-inosine, belongs to the class of organic compounds known as purine nucleosides. Purine nucleosides are compounds comprising a purine base attached to a ribosyl or deoxyribosyl sugar moiety. Guanosine consists of a guanine base attached to a ribose (ribofuranose) ring via a beta-N9-glycosidic bond. Guanosine is a white, crystalline powder with no odor and mild saline taste. It is very soluble in acetic acid, and slightly soluble in water, but insoluble in ethanol, diethyl ether, benzene, and chloroform. Guanosine exists in all living species, ranging from bacteria to plants to humans. High levels of guanosine can be found in clovers, coffee plants, and the pollen of pines. It has been detected, but not quantified in, several different foods, such as leeks, garlic, chicory roots, green bell peppers, and black-eyed peas. Guanosine plays an important role in various biochemical processes including the synthesis of nucleic acids such as RNA and intracellular signal transduction (cGMP). The antiviral drug acyclovir, often used in herpes treatment, and the anti-HIV drug abacavir, are both structurally similar to guanosine. Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate (cGMP), guanosine diphosphate (GDP), and guanosine triphosphate (GTP). In humans, guanosine is involved in intracellular signalling through the adenosine receptors A1R and A2AR (PMID: 31847113). Evidence from rodent and cell models has shown a number of important neurotrophic and neuroprotective effects of guanosine. In particular, it is effective in preventing deleterious consequences of seizures, spinal cord injury, pain, mood disorders and aging-related diseases, such as ischemia, Parkinson’s and Alzheimer’s diseases (PMID: 27699087). Studies with rodent models of Parkinson’s disease have shown that guanosine decreases neuronal apoptotic cell death and increases dopaminergic neurons at substantia nigra pars compacta, accompanied by an improvement of motor symptoms in Parkinson’s disease (i.e. a reduction of bradykinesia). Guanosine promotes neurite arborization, outgrowth, proliferation and differentiation. Systemic administration of guanosine for eight weeks (8 mg/kg) has been shown to stimulate neuroprogenitors proliferation in the subventricular zone (SVZ) in a mouse model of Parkinsonism (PMID: 27699087). The effect of guanosine treatment is accompanied by an increased number of fibroblast growth factor (FGF-2)-positive cells which is an important regulator of neuroprogenitor/stem cell proliferation, survival and differentiation (PMID: 27699087). Guanosine prevents reactive oxygen species (ROS) generation and cell death in hippocampal slices subjected to the oxygen/glucose deprivation (PMID: 31847113).

9-beta-D-arabinofuranosylguanine is a purine nucleoside in which guanine is attached to arabinofuranose via a beta-N(9)-glycosidic bond. It inhibits DNA synthesis and causes cell death. It has a role as an antineoplastic agent and a DNA synthesis inhibitor. It is a beta-D-arabinoside and a purine nucleoside.

Crotonoside is a purine nucleoside. Crotonoside is a natural product found in Croton tiglium with data available.

2'-O-Methyladenosine is a methylated adenine residue. 2'-O-Methyladenosine is a naturally occurring 2'-O-methylpurine nucleoside with long lasting hypotensive properties; resistance of 2'-O-methyladenosine against adenosine deaminase is thought to contribute to prolonged activity. 2'-O-Methyladenosine occurs in human fluids, and they increase in urines of untreated adenosine deaminase (ADA) deficient patients (OMIM 608958). (PMID: 9539952, 6980397).

N-Acetyl-D-Glucosamine 6-Phosphate is an intermediate in the metabolism of Aminosugars. It is a substrate for Glucosamine 6-phosphate N-acetyltransferase.

1-Methyladenosine, also known as M1A, belongs to the class of organic compounds known as purine nucleosides. Purine nucleosides are compounds comprising a purine base attached to a ribosyl or deoxyribosyl moiety. Precise m6A mapping by m6A-CLIP/IP (briefly m6A-CLIP) revealed that a majority of m6A locates in the last exon of mRNAs in multiple tissues/cultured cells of mouse and human, and the m6A enrichment around stop codons is a coincidence that many stop codons locate round the start of last exons where m6A is truly enriched. The methylation of adenosine is directed by a large m6A methyltransferase complex containing METTL3 as the SAM-binding sub-unit. Insulin-like growth factor-2 mRNA-binding proteins 1, 2, and 3 (IGF2BP1-3) are reported as a novel class of m6A readers.

A galactosamine phosphate that is N-acetyl-D-galactosamine substituted at position 1 by a monophosphate group." []

3-O-Methyladenosine is a methylated adenine residue.

A 2-acetamido-2-deoxy-D-glucopyranose 1-phosphate having alpha-configuration at the anomeric centre." []

N-Acetyl-D-mannosamine 6-phosphate is an intermediate in amino sugar metabolism and is a substrate for UDP-N-acetylglucosamine--peptide N-acetylglucosaminyltransferase, Bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, Alpha-N-acetylglucosaminidase and Exostosin-2. It can be generated from N-acetyl-neuraminate-9-phosphate or N-acetyl-D-mannosamine.

N-acetyl-alpha-d-galactosamine 1-phosphate is part of the Galactose metabolism, and Amino sugar and nucleotide sugar metabolism pathways. It is a substrate for: N-acetylgalactosamine kinase.

N6-Methyladenosine is a methylated adenine residue. N6-Methyladenosine is an endogenous urinary nucleoside product of the degradation of transfer ribonucleic acid (tRNA); urinary nucleosides are biological markers for patients with colorectal cancer. tRNA has been shown to be excreted in abnormal amounts in the urine of cancer patients. tRNA from neoplastic tissue had a much more rapid turnover rate than the tRNA from the corresponding normal tissue. Evidence indicates that methylation of tRNA occurs only after synthesis of the intact macromolecule. Because there are no specific enzyme systems to incorporate the modified nucleosides into the macromolecular nucleic acid, these nucleosides once released in the process of tRNA turnover cannot be reutilized, nor are they further degraded, but are excreted in urine. (PMID: 15991285, 3506820).

Dyspropterin, an intermediate formed from dihydroneopterin triphosphate in the biosynthetic pathway of tetrahydrobiopterin.

Morphinone is a very strong opioid. It is an intermediary substance in synthesises of semi-synthetic opioids, e.g. Naloxone and Naltrexone and Oxycodone.

Tyrosyl-Threonine is a dipeptide composed of tyrosine and threonine. It is an incomplete breakdown product of protein digestion or protein catabolism. Some dipeptides are known to have physiological or cell-signaling effects although most are simply short-lived intermediates on their way to specific amino acid degradation pathways following further proteolysis. This dipeptide has not yet been identified in human tissues or biofluids and so it is classified as an 'Expected' metabolite.

N-Phenylacetylphenylalanine (PAP) is a peptide analogue used as a potential antisickling agent. This biaromatic agent has properties that make it a suitable candidate for the development of a useful therapeutic agent for the treatment of sickle cell disease. (PMID: 3663644, 6587344).

Threonyltyrosine is a dipeptide composed of threonine and tyrosine. It is an incomplete breakdown product of protein digestion or protein catabolism. Dipeptides are organic compounds containing a sequence of exactly two alpha-amino acids joined by a peptide bond. Some dipeptides are known to have physiological or cell-signalling effects although most are simply short-lived intermediates on their way to specific amino acid degradation pathways following further proteolysis.

A carbohydrate acid derivative comprising D-galactonic acid having the 2-hydroxy group replaced by acetamido." []

P-coumaroyltyramine belongs to coumaric acids and derivatives class of compounds. Those are aromatic compounds containing Aromatic compounds containing a cinnamic acid moiety (or a derivative thereof) hydroxylated at the C2 (ortho-), C3 (meta-), or C4 (para-) carbon atom of the benzene ring. P-coumaroyltyramine is practically insoluble (in water) and a very weakly acidic compound (based on its pKa). P-coumaroyltyramine can be found in a number of food items such as small-leaf linden, mamey sapote, pepper (c. frutescens), and beech nut, which makes P-coumaroyltyramine a potential biomarker for the consumption of these food products.