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N-Acetyl-L-methionine or N-Acetylmethionine, belongs to the class of organic compounds known as N-acyl-alpha amino acids. N-acyl-alpha amino acids are compounds containing an alpha amino acid which bears an acyl group at its terminal nitrogen atom. N-Acetylmethionine can also be classified as an alpha amino acid or a derivatized alpha amino acid. Technically, N-Acetylmethionine is a biologically available N-terminal capped form of the proteinogenic alpha amino acid L-methionine. N-acetyl amino acids can be produced either via direct synthesis of specific N-acetyltransferases or via the proteolytic degradation of N-acetylated proteins by specific hydrolases. N-terminal acetylation of proteins is a widespread and highly conserved process in eukaryotes that is involved in protection and stability of proteins (PMID: 16465618). About 85% of all human proteins and 68% of all yeast proteins are acetylated at their N-terminus (PMID: 21750686). Several proteins from prokaryotes and archaea are also modified by N-terminal acetylation. The majority of eukaryotic N-terminal-acetylation reactions occur through N-acetyltransferase enzymes or NAT’s (PMID: 30054468). These enzymes consist of three main oligomeric complexes NatA, NatB, and NatC, which are composed of at least a unique catalytic subunit and one unique ribosomal anchor. The substrate specificities of different NAT enzymes are mainly determined by the identities of the first two N-terminal residues of the target protein. The human NatA complex co-translationally acetylates N-termini that bear a small amino acid (A, S, T, C, and occasionally V and G) (PMID: 30054468). NatA also exists in a monomeric state and can post-translationally acetylate acidic N-termini residues (D-, E-). NatB and NatC acetylate N-terminal methionine with further specificity determined by the identity of the second amino acid. N-acetylated amino acids, such as N-acetylmethionine can be released by an N-acylpeptide hydrolase from peptides generated by proteolytic degradation (PMID: 16465618). In addition to the NAT enzymes and protein-based acetylation, N-acetylation of free methionine can also occur. In particular, N-Acetylmethionine can be biosynthesized from L-methionine and acetyl-CoA by the enzyme methionine N-acetyltransferase (EC 2.3.1.66). Excessive amounts N-acetyl amino acids including N-acetylmethionine (as well as N-acetylglycine, N-acetylserine, N-acetylglutamine, N-acetylglutamate, N-acetylalanine, N-acetylleucine and smaller amounts of N-acetylthreonine, N-acetylisoleucine, and N-acetylvaline) can be detected in the urine with individuals with acylase I deficiency, a genetic disorder (PMID: 16465618). Aminoacylase I is a soluble homodimeric zinc binding enzyme that catalyzes the formation of free aliphatic amino acids from N-acetylated precursors. In humans, Aminoacylase I is encoded by the aminoacylase 1 gene (ACY1) on chromosome 3p21 that consists of 15 exons (OMIM 609924). Individuals with aminoacylase I deficiency will experience convulsions, hearing loss and difficulty feeding (PMID: 16465618). ACY1 can also catalyze the reverse reaction, the synthesis of acetylated amino acids. Many N-acetylamino acids, including N-acetylmethionine are classified as uremic toxins if present in high abundance in the serum or plasma (PMID: 26317986; PMID: 20613759). Uremic toxins are a diverse group of endogenously produced molecules that, if not properly cleared or eliminated by the kidneys, can cause kidney damage, cardiovascular disease and neurological deficits (PMID: 18287557).

A racemate comprising equimolar amounts of N-acetyl-L-methionine and N-acetyl-D-methionine." []

2-Hydroxybenzaldehyde, also known as salicylal or O-formylphenol, belongs to the class of organic compounds known as hydroxybenzaldehydes. These are organic aromatic compounds containing a benzene ring carrying an aldehyde group and a hydroxyl group. 2-Hydroxybenzaldehyde is a cinnamon, cooling, and medical tasting compound. 2-Hydroxybenzaldehyde is found, on average, in the highest concentration within peppermints. 2-Hydroxybenzaldehyde has also been detected, but not quantified, in several different foods, such as common buckwheats, garden tomato (var.), herbs and spices, and tea. This could make 2-hydroxybenzaldehyde a potential biomarker for the consumption of these foods. 2-Hydroxybenzaldehyde is a potentially toxic compound.

Anabasine is a pyridine and piperidine alkaloid found in the Tree Tobacco (Nicotiana glauca) plant, a close relative of the common tobacco plant (Nicotiana tabacum). It is a structural isomer of, and chemically similar to, nicotine. Its principal (historical) industrial use is as an insecticide. Anabasine is a nicotinic receptor agonist toxin and Cholinesterase inhibitor which acts upon the nicotinic acetylcholine receptors. Anabasine is an unstable yellow liquid which is succeptable to light, heat and moisture. It's decomposition products include Nitrogen oxides, carbon monoxide, irritating and toxic fumes and gases and carbon dioxide.

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).

Epinephrine is a catecholamine, a sympathomimetic monoamine derived from the amino acids phenylalanine and tyrosine. It is the active sympathomimetic hormone secreted from the adrenal medulla in most species. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. It is used in asthma and cardiac failure and to delay absorption of local anesthetics. Epinephrine also constricts arterioles in the skin and gut while dilating arterioles in leg muscles. It elevates the blood sugar level by increasing hydrolysis of glycogen to glucose in the liver, and at the same time begins the breakdown of lipids in adipocytes. Epinephrine has a suppressive effect on the immune system.

Normetanephrine, also known as normetadrenaline or N111, belongs to the class of organic compounds known as methoxyphenols. Methoxyphenols are compounds containing a methoxy group attached to the benzene ring of a phenol moiety. Normetanephrine is a solid that is soluble in water. Normetanephrine is a metabolite of norepinephrine created by action of catechol-O-methyl transferase on norepinephrine. Within humans, normetanephrine participates in a number of enzymatic reactions. In particular, normetanephrine can be converted into 3-methoxy-4-hydroxyphenylglycolaldehyde through its interaction with the enzyme amine oxidase [flavin-containing] A. It is also involved in the metabolic disorder called transient tyrosinemia of the newborn. This compound is excreted in the urine and is found in certain tissues. It is a marker for catecholamine-secreting tumors such as pheochromocytoma (PMID: 30538672).

4-amino-4-deoxychorismate, also known as adc, belongs to dicarboxylic acids and derivatives class of compounds. Those are organic compounds containing exactly two carboxylic acid groups. 4-amino-4-deoxychorismate is soluble (in water) and a weakly acidic compound (based on its pKa). 4-amino-4-deoxychorismate can be found in a number of food items such as chives, narrowleaf cattail, green vegetables, and chicory leaves, which makes 4-amino-4-deoxychorismate a potential biomarker for the consumption of these food products. 4-amino-4-deoxychorismate exists in E.coli (prokaryote) and yeast (eukaryote).

Protocatechuic acid 4-glucoside is a member of the class of compounds known as phenolic glycosides. Phenolic glycosides are organic compounds containing a phenolic structure attached to a glycosyl moiety. Some examples of phenolic structures include lignans, and flavonoids. Among the sugar units found in natural glycosides are D-glucose, L-Fructose, and L rhamnose. Protocatechuic acid 4-glucoside is soluble (in water) and a weakly acidic compound (based on its pKa). Protocatechuic acid 4-glucoside can be found in a number of food items such as rosemary, jostaberry, rubus (blackberry, raspberry), and highbush blueberry, which makes protocatechuic acid 4-glucoside a potential biomarker for the consumption of these food products.

A monohydroxybenzoic acid that is 2,5-dihydroxybenzoic acid in which the phenolic hydrogen at position 2 has been replaced by a beta-D-glucosyl residue." []

Dimethyl maleate belongs to the class of organic compounds known as fatty acid esters. These are carboxylic ester derivatives of a fatty acid. Dimethyl maleate is the methyl ester of maleic acid and the cis-isomer of dimethyl fumarate. Dimethyl maleate is a commonly used thiol-alkylating agent and enjoys widespread use in many organic synthesis (e.g. as a dienophile for diene syntheses). In the production of plastics, pigments, pharmaceuticals, and agricultural products, dimethyl maleate is used as an additive and an intermediate. In the production of paints, adhesives, and copolymers, dimethyl maleate is used as an intermediate.

Folic acid or folate, is a vitamin that belongs to the class of compounds known as pterins. Chemically, folate consists of three distinct chemical moieties linked together. A pterin (2-amino-4-hydroxy-pteridine) linked by a methylene bridge to a p-aminobenzoyl group that in turn is linked through an amide linkage to glutamic acid. It is a member of the vitamin B family and is primarily known as vitamin B9. Folate is required for the body to make DNA and RNA and metabolize amino acids necessary for cell division for the hematopoietic system. As humans cannot make folate, it is required in the diet, making it an essential nutrient (i.e. a vitamin). Folate occurs naturally in many foods including mushrooms, spinach, yeast, green leaves, and grasses (poaceae). Folic acid, being biochemically inactive, is converted to tetrahydrofolic acid and methyltetrahydrofolate by the enzyme known as dihydrofolate reductase. Tetrahydrofolate and methyltetrahydrofolate are transported across cells by receptor-mediated endocytosis where they are needed to maintain normal erythropoiesis, synthesize purine and thymidylate nucleic acids, interconvert amino acids and generate formic acid. Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia. Folic acid is also used as a supplement by women during pregnancy to reduce the risk of neural tube defects (NTDs) in babies. Low levels in early pregnancy are believed to be the cause of more than half of babies born with NTDs (PMID: 28097362). Folic acid is also a microbial metabolite produced by Bifidobacterium and Lactobacillus (PMID: 22254078).

Theobromine, or 3,7-Dimethylxanthine, is the principle alkaloid in Theobroma cacao (the cacao bean) and other plants. A xanthine alkaloid that is used as a bronchodilator and as a vasodilator. It has a weaker diuretic activity than theophylline and is also a less powerful stimulant of smooth muscle. It has practically no stimulant effect on the central nervous system. It was formerly used as a diuretic and in the treatment of angina pectoris and hypertension. Theobromine is a bitter alkaloid of the methylxanthine family, which also includes the similar compounds theophylline and caffeine. Despite its name, the compound contains no bromine. Theobromine is derived from Theobroma, the genus of the cacao tree, which is composed of the Greek roots theo ("God") and broma ("food"), meaning "food of the gods". It is the primary alkaloid found in cocoa and chocolate, and is one of the causes for chocolate's mood-elevating effects. The amount found in chocolate is small enough that chocolate can be safely consumed by humans in large quantities, but animals that metabolize theobromine more slowly, such as cats and dogs, can easily consume enough chocolate to cause chocolate poisoning. Theobromine is a stimulant frequently confused with caffeine. Theobromine has very different effects on the human body from caffeine; it is a mild, lasting stimulant with a mood improving effect, whereas caffeine has a strong, immediate effect and increases stress. In medicine, it is used as a diuretic, vasodilator, and myocardial stimulant. There is a possible association between prostate cancer and theobromine. Theobromine is a contributing factor in acid reflux because it relaxes the esophageal sphincter muscle, allowing stomach acid access to the esophagus.

3-O-Methyladenosine is a methylated adenine residue.

4-hydroxy-2-oxo-Heptanedioic acid

2,4-dihydroxy-2-heptenedioc acid

Ribothymidine 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. When chemical bonds to DNA, the DNA becomes damaged and proper and complete replication cannot occur to make the normal intended cell. A DNA adduct is an abnormal piece of DNA covalently-bonded to a cancer-causing chemical. This has shown to be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as bio-markers and as such are themselves measured to reflect quantitatively, for comparison, the amount of cancer in the subject. (PMID:3506820, 17044778, 17264127, 16799933).

Isoleucyl-Glutamate is a dipeptide composed of isoleucine and glutamate. 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.

3-Dehydroquinic acid belongs to the class of organic compounds known as alpha-hydroxy acids and derivatives. These are organic compounds containing a carboxylic acid substituted with a hydroxyl group on the adjacent carbon. 3-Dehydroquinic acid is an extremely weak basic (essentially neutral) compound (based on its pKa). In most organisms, 3-dehydroquinic acid is synthesized from D-erythrose-4-phosphate in two steps. However, archaea genomes contain no orthologs for the genes that encode these first two steps. Instead, archaeabacteria appear to utilize an alternative pathway in which 3-dehydroquinic acid is synthesized from 6-deoxy-5-ketofructose-1-phosphate and L-aspartate-semialdehyde. These two compounds are first condensed to form 2-amino-3,7-dideoxy-D-threo-hept-6-ulosonate, which cyclizes to 3-dehydroquinic acid. From 3-dehydroquinic acid and on to chorismate, the archaeal pathway appears to be identical to the bacterial pathway.

Vanilloyl glucose is a member of the class of compounds known as hydrolyzable tannins. Hydrolyzable tannins are tannins with a structure characterized by either of the following models. In model 1, the structure contains galloyl units (in some cases, shikimic acid units) are linked to diverse polyol carbohydrate-, catechin-, or triterpenoid units. In model 2, contains at least two galloyl units C-C coupled to each other, and do not contain a glycosidically linked catechin unit. Vanilloyl glucose is soluble (in water) and a very weakly acidic compound (based on its pKa). Vanilloyl glucose can be found in a number of food items such as orange bell pepper, yellow bell pepper, pepper (c. annuum), and red bell pepper, which makes vanilloyl glucose a potential biomarker for the consumption of these food products.