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(±)-erythro-Isoleucine is a flavouring ingredient, dietary supplement, and a nutrient. Branched-chain amino acids (BCAA) are essential amino acids whose carbon structure is marked by a branch point. These three amino acids are critical to human life and are particularly involved in stress, energy and muscle metabolism. BCAA supplementation as therapy, both oral and intravenous, in human health and disease holds great promise. BCAA denotes valine, isoleucine, and leucine which are branched chain essential amino acids. Despite their structural similarities, the branched amino acids have different metabolic routes, with valine going solely to carbohydrates, leucine solely to fats, and isoleucine to both. The different metabolism accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg, and 16 mg/kg of valine, leucine, and isoleucine respectively. Furthermore, these amino acids have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. BCAA are decreased in patients with liver disease such as hepatitis, hepatic coma, cirrhosis, extrahepatic biliary atresia, or portacaval shunt. Aromatic amino acids (AAA)-tyrosine, tryptophan, and phenylalanine (as well as methionine) are increased in these conditions. Valine, in particular, has been established as a useful supplemental therapy to the ailing liver. All the BCAA probably compete with AAA for absorption into the brain. Supplemental BCAA with vitamin B6 and zinc help normalize the BCAA:AAA ratio. The BCAA are not without side effects. Leucine alone, for example, exacerbates pellagra and can cause psychosis in pellagra patients by increasing excretion of niacin in the urine. Leucine may lower brain serotonin and dopamine. The ratio of leucine to other BCAA is greatest in pork, where leucine is 7 to 8 g and the other BCAA together are only 3 to 4 g (http://www.dcnutrition.com).

Isoleucine (Ile) or L-isoleucine is an alpha-amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. L-isolecuine is one of 20 proteinogenic amino acids, i.e., the amino acids used in the biosynthesis of proteins. Isoleucine is found in all organisms ranging from bacteria to plants to animals. It is classified as a non-polar, uncharged (at physiological pH) aliphatic amino acid. Isoleucine is an essential amino acid in humans, meaning the body cannot synthesize it and that it must be obtained from the diet. In plants and microorganisms, isoleucine is synthesized starting from pyruvate and alpha-ketobutyrate. Isoleucine is classified as a branched chain amino acid (BCAA). BCAAs include three amino acids: isoleucine, leucine and valine. They are alpha amino acids whose carbon structure is marked by a beta branch point. Despite their structural similarities, BCAAs have different metabolic routes, with valine going solely to carbohydrates (glucogenic), leucine solely to fats (ketogenic) and isoleucine being both a glucogenic and a ketogenic amino acid. Isoleucine is catabolized via with alpha-ketoglutarate where upon it is oxidized and split into propionyl-CoA and acetyl-CoA. Propionyl-CoA is converted into succinyl-CoA, a TCA cycle intermediate which can be converted into oxaloacetate for gluconeogenesis (hence glucogenic). The acetyl-CoA can be fed into the TCA cycle by condensing with oxaloacetate to form citrate or used in the synthesis of ketone bodies or fatty acids. The different metabolism of BCAAs accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg and 16 mg/kg of valine, leucine and isoleucine are required respectively. Furthermore, these amino acids have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. BCAAs are decreased in patients with liver disease, such as hepatitis, hepatic coma, cirrhosis, extrahepatic biliary atresia. An inability to break down isoleucine, along with other amino acids, is associated with maple syrup urine disease (MSUD) (PMID: 34125801). Isoleucine, like other BCAAs, is associated with insulin resistance. In particular, higher levels of isoleucine are observed in the blood of diabetic mice, rats, and humans (PMID 25287287). Mice fed an isoleucine deprivation diet for one day have improved insulin sensitivity, and feeding of an isoleucine deprivation diet for one week significantly decreases blood glucose levels (PMID: 24684822).

L-Norleucine, also known as L-aminohexanoate or caprine, belongs to the class of organic compounds known as l-alpha-amino acids. These are alpha amino acids which have the L-configuration of the alpha-carbon atom. Thus, L-norleucine is considered to be a fatty acid lipid molecule. An unnatural amino acid that is used experimentally to study protein structure and function. L-Norleucine is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. L-Norleucine exists in all eukaryotes, ranging from yeast to humans. Outside of the human body, L-Norleucine has been detected, but not quantified in cow milk. This could make L-norleucine a potential biomarker for the consumption of these foods. It binds reversibly to the kringle domain of plasminogen and blocks the binding of plasminogen to fibrin and its activation to plasmin.

2-Amino-4-methylpentanoic acid

Leucine (Leu) or L-leucine is an alpha-amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. L-leucine is one of 20 proteinogenic amino acids, i.e., the amino acids used in the biosynthesis of proteins. Leucine is found in all organisms ranging from bacteria to plants to animals. It is classified as a non-polar, uncharged (at physiological pH) aliphatic amino acid. Leucine is essential in humans, meaning the body cannot synthesize it, and it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, beans and legumes. L-Leucine is a branched chain amino acid (BCAA). The BCAAs consist of leucine, valine and isoleucine (and occasionally threonine). BCAAs are essential amino acids whose carbon structure is marked by a branch point at the beta-carbon position. BCAAs are critical to human life and are particularly involved in stress, energy and muscle metabolism. BCAA supplementation as therapy, both oral and intravenous, in human health and disease holds great promise. BCAAs have different metabolic routes, with valine going solely to carbohydrates (glucogenic), leucine solely to fats (ketogenic) and isoleucine being both a glucogenic and a ketogenic amino acid. The different metabolism accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg and 16 mg/kg of valine, leucine and isoleucine respectively. The primary metabolic end products of leucine metabolism are acetyl-CoA and acetoacetate; consequently, it is one of the two exclusively ketogenic amino acids, with lysine being the other. Leucine is the most important ketogenic amino acid in humans. The vast majority of l-leucine metabolism is initially catalyzed by the branched-chain amino acid aminotransferase enzyme, producing alpha-ketoisocaproate (alpha-KIC). alpha-KIC is metabolized by the mitochondrial enzyme branched-chain alpha-ketoacid dehydrogenase, which converts it to isovaleryl-CoA. Isovaleryl-CoA is subsequently metabolized by the enzyme isovaleryl-CoA dehydrogenase and converted to beta-methylcrotonyl-CoA (MC-CoA), which is used in the synthesis of acetyl-CoA and other compounds. During biotin deficiency, HMB can be synthesized from MC-CoA via enoyl-CoA hydratase and an unknown thioesterase enzyme, which convert MC-CoA into HMB-CoA and HMB-CoA into HMB respectively. Leucine has the capacity to directly stimulate myofibrillar muscle protein synthesis (PMID 15051860). This effect of leucine arises results from its role as an activator of the mechanistic target of rapamycin (mTOR) (PMID 23551944) a serine-threonine protein kinase that regulates protein biosynthesis and cell growth. The activation of mTOR by leucine is mediated through Rag GTPases. Leucine, like other BCAAs, is associated with insulin resistance. In particular, higher levels of leucine are observed in the blood of diabetic mice, rats, and humans (PMID 25287287). BCAAs such as leucine have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. Persistently low leucine levels can result in decreased appetite, poor feeding, lethargy, poor growth, weight loss, skin rashes, hair loss, and desquamation. Many types of inborn errors of BCAA metabolism exist and these are marked by various abnormalities. The most common form is maple syrup urine disease, marked by a characteristic urinary odor. Other abnormalities are associated with a wide range of symptoms, such as mental retardation, ataxia, hypoglycemia, spinal muscle atrophy, rash, vomiting and excessive muscle movement. Most forms of BCAA metabolism errors are corrected by dietary restriction of BCAAs and at least one form is correctable by supplementation with 10 mg of biotin daily. - BCAAs are useful because they are metabolized primarily by muscle. Stress states - e.g surgery, trauma, cirrhosis, infections, fever and starvation--require proportionately more BCAAs than other amino acids and probably proportionately more leucine than either valine or isoleucine. BCAAs and other amino acids are frequently fed intravenously (TPN) to malnourished surgical patients and in some cases of severe trauma. BCAAs, particularly leucine, stimulate protein synthesis, increase reutilization of amino acids in many organs and reduce protein breakdown. Furthermore, leucine can be an important source of calories, and is superior as fuel to the ubiquitous intravenous glucose (dextrose). - Leucine also stimulates insulin release, which in turn stimulates protein synthesis and inhibits protein breakdown. These effects are particularly useful in athletic training. Huntington's chorea and anorexic disorders both are characterized by low serum BCAAs. These diseases, as well as forms of Parkinson's, may respond to BCAA therapy.

L-alloisoleucine is a branched chain amino acid and is a stereo-isomer of L-isoleucine. It is a common constituent of human plasma (albeit at low levels). L-alloisoleucine is produced as a byproduct of isoleucine transamination. L-Isoleucine is one of the four common amino acids (the 3 others being threonine, hydroxyproline, and hydroxylysine) that have two asymmetric carbon atoms which produce four structural possibilities for the same chemical composition. L-alloisoleucine differs from L-isoleucine by having having different stereochemistry around its beta carbon. Plasma L-alloisoleucine, which is derived from L-isoleucine in vivo, can be used for the diagnosis of maple syrup urine disease (MSUD), a genetic disorder. Indeed, plasma L-alloisoleucine levels above 5 umol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD (PMID: 10508118). In MSUD the degradation of the essential branched-chain L-amino acids leucine, valine, and isoleucine and their derived 2-oxoacids is impaired because of an inherited deficiency in branched-chain 2-oxoacid dehydrogenase complex (EC 1.2.4.4) activity. The accumulation of branched-chain compounds in blood and other body fluids can exert neurotoxic effects.

Creatine, is a naturally occurring non-protein compound. It belongs to the class of organic compounds known as alpha amino acids and derivatives. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon), or a derivative thereof. Creatine is found in all vertebrates where it facilitates recycling of adenosine triphosphate (ATP). Its primary metabolic role is to combine with a phosphoryl group, via the enzyme creatine kinase, to generate phosphocreatine, which is used to regenerate ATP. Most of the human body's total creatine and phosphocreatine stores are found in skeletal muscle (95%), while the remainder is distributed in the blood, brain, testes, and other tissues. Creatine is not an essential nutrient as it is naturally produced in the human body from the amino acids glycine and arginine, with an additional requirement for methionine to catalyze the transformation of guanidinoacetate to creatine. In the first step of its biosynthesis glycine and arginine are combined by the enzyme arginine:glycine amidinotransferase (AGAT) to form guanidinoacetate, which is then methylated by guanidinoacetate N-methyltransferase (GAMT), using S-adenosyl methionine as the methyl donor. Creatine can also be obtained through the diet at a rate of about 1 gram per day from an omnivorous diet. A cyclic form of creatine, called creatinine, exists in equilibrium with its tautomer and with creatine. Clinically, there are three distinct disorders of creatine metabolism. Deficiencies in the two synthesis enzymes (AGAT and GAMT) can cause L-arginine:glycine amidinotransferase deficiency (caused by variants in AGAT) and guanidinoacetate methyltransferase deficiency (caused by variants in GAMT). Both disorders are inherited in an autosomal recessive manner. A third defect, creatine transporter defect, is caused by mutations in SLC6A8 and inherited in a X-linked manner. Creatine is widely used as a supplement by athletes. Its use can increase maximum power and performance in high-intensity anaerobic repetitive work (periods of work and rest) by 5 to 15% (PMID: 24688272). Creatine has no significant effect on aerobic endurance, although it will increase power during short sessions of high-intensity aerobic exercise (PMID: 9662683).

The D-enantiomer of isoleucine." []

Beta-Guanidinopropionic acid is analog of creatine and is reported to decrease phosphocreatine and ATP content in animal tissues in vivo.

An N-alkyl glycine that is glycine in which the amino group is replaced by a diethylnitrilo group." []

Dihydrouracil belongs to the class of organic compounds known as pyrimidones. Pyrimidones are compounds that contain a pyrimidine ring, which bears a ketone. Pyrimidine is a 6-membered ring consisting of four carbon atoms and two nitrogen centers at the 1- and 3- ring positions. Dihydrouracil is an intermediate breakdown product of uracil. Dihydrouracil exists in all living organisms, ranging from bacteria to plants to humans. Within humans, dihydrouracil participates in a number of enzymatic reactions. In particular, dihydrouracil can be biosynthesized from uracil; which is mediated by the enzyme dihydropyrimidine dehydrogenase [NADP(+)]. The breakdown of uracil is a multistep reaction that leads to the production of beta-alanine. The reaction process begins with the enzyme known as dihydropyrimidine dehydrogenase (DHP), which catalyzes the reduction of uracil into dihydrouracil. Then the enzyme known as dihydropyrimidinase hydrolyzes dihydrouracil into N-carbamyl-beta-alanine. Finally, beta-ureidopropionase catalyzes the conversion of N-carbamyl-beta-alanine into beta-alanine. There is at least one metabolic disorder that is associated with altered levels of dihydrouracil. In particular, dihydropyrimidinase deficiency is an inborn metabolic disorder that leads to highly increased concentrations of dihydrouracil and 5,6-dihydrothymine, and moderately increased concentrations of uracil and thymine in urine. Dihydropyrimidinase deficiency can cause neurological and gastrointestinal problems in some affected individuals (OMIM: 222748). In particular, patients with dihydropyrimidinase deficiency exhibit a number of neurological abnormalities including intellectual disability, seizures, weak muscle tone (hypotonia), an abnormally small head size (microcephaly), and autistic behaviours that affect communication and social interaction. Gastrointestinal problems that occur in dihydropyrimidinase deficiency include backflow of acidic stomach contents into the esophagus (gastroesophageal reflux) and recurrent episodes of vomiting.

A glycine derivative that is glycine with a tertiary butyl group at position 2." []

ε-Caprolactone, also known simply as caprolactone, is a compound belonging to the family of compounds known as lactones. Lactones are cyclic esters of hydroxyl carboxylic acids, wherein the functional group has become part of a ring structure with carbon atoms. Caprolactone consists of a seven membered ring derived from the cyclization of caproic acid. As a monomer it used in the production of highly specialized plastics and polymers. Caprolactone is produced by the Baeyer-Villiger oxidation of cyclohexanone with peracetic acid, and was used previously (until economically inviable) as a precursor in the production of caprolactam. Several other caprolactone isomers are known. These isomers include α-, β-, γ-, and δ-caprolactones. All are chiral. (R)-γ-caprolactone is a component of floral scents and of the aromas of some fruits and vegetables (Journal of Agricultural and Food Chemistry. 37: 413–418), while δ-caprolactone is found in heated milk fat (Journal of Dairy Science. 48 (5): 615–616).

N-methylvaline, also known as MeVal, D-Valine, or N-Methyl-L-valine, is an N-methylamino acid that is the N-methyl derivative of valine. It functions as a bronsted acid, a molecular entity capable of donating a hydron to an acceptor (Bronsted base) via oxoacid

D-alloisoleucine is an alloisoleucine and a D-alpha-amino acid. It is an enantiomer of a L-alloisoleucine. It is a tautomer of a D-alloisoleucine zwitterion.

3-Methylindole, or skatole, belongs to the indole family and has a methyl substituent in position 3 of the indole ring. It occurs naturally in feces, beets, and coal tar, and has a strong fecal odor. Its name is derived from skato, the Greek word for dung. It exists as a white crystalline or fine powder solid, and it browns upon aging. 3-Methylindole is produced from tryptophan in the mammalian digestive tract where tryptophan is converted to indoleacetic acid, which decarboxylates to give the methylindole. These reactions are largely driven by the microbiota in the digestive tract. 3-Methylindole is soluble in alcohol and benzene and it gives violet color in potassium ferrocyanide (K4Fe(CN)6.3H2O) mixed with sulfuric acid (H2SO4). Skatole has a double ring system which displays aromaticity that comes from the lone pair electrons on the nitrogen. It is continuous (all atoms in the ring are sp2 hybridized), planar, and follows the 4n+2 rule because it has 10 pi electrons. In a 1994 report released by five top cigarette companies, skatole was listed as one of the 599 additives to cigarettes. This is because in low concentrations skatole has a flowery smell and is found in several flowers and essential oils, including those of orange blossoms, jasmine, and Ziziphus mauritiana. As a result, skatole/3-methylindole is used as a fragrance and fixative in many perfumes and as a general aroma compound for other applications. 3-Methylindole has been found to be a bacterial metabolite of members of the Clostridium (PMID: 18223109) and Lactobacillus (PMID: 16345702) families. Skatole functions as an insect attractant and is one of many compounds that are attractive to males of various species of orchid bees, which apparently gather the chemical to synthesize pheromones; it is commonly used as bait for these bees for study (PMID: 12647866). It is also known for being an attractant for the Tasmanian grass grub beetle (Aphodius tasmaniae). Skatole has also been shown to be an attractant to gravid mosquitoes in both field and laboratory conditions (PMID: 24242053).

2-methyl-1H-indole is a methylindole that is 1H-indole substituted by a methyl group at position 2. It derives from a hydride of a 1H-indole.

An essential branched-chain amino acid important for hemoglobin formation. [PubChem]; Branched chain amino acids (BCAA) are essential amino acids whose carbon structure is marked by a branch point. These three amino acids are critical to human life and are particularly involved in stress, energy and muscle metabolism. BCAA supplementation as therapy, both oral and intravenous, in human health and disease holds great promise. 'BCAA' denotes valine, isoleucine and leucine which are branched chain essential amino acids. Despite their structural similarities, the branched amino acids have different metabolic routes, with valine going solely to carbohydrates, leucine solely to fats and isoleucine to both. The different metabolism accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg and 16 mg/kg of valine, leucine and isoleucine respectively. Furthermore, these amino acids have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. Many types of inborn errors of BCAA metabolism exist, and are marked by various abnormalities. The most common form is the maple syrup urine disease, marked by a characteristic urinary odor. Other abnormalities are associated with a wide range of symptoms, such as mental retardation, ataxia, hypoglycemia, spinal muscle atrophy, rash, vomiting and excessive muscle movement. Most forms of BCAA metabolism errors are corrected by dietary restriction of BCAA and at least one form is correctable by supplementation with 10 mg of biotin daily. BCAA are useful because they are metabolized primarily by muscle. Stress state- e.g surgery, trauma, cirrhosis, infections, fever and starvation--require proportionately more BCAA than other amino acids and probably proportionately more leucine than either valine or isoleucine. BCAA and other amino acids are frequently fed intravenously (TPN) to malnourished surgical patients and in some cases of severe trauma. BCAA, particularly leucine, stimulate protein synthesis, increase reutilization of amino acids in many organs and reduce protein breakdown. Furthermore, leucine can be an important source of calories, and is superior as fuel to the ubiquitous intravenous glucose (dextrose). Leucine also stimulates insulin release, which in turn stimulates protein synthesis and inhibits protein breakdown. These effects are particularly useful in athletic training. BCAA should also replace the use of steroids as commonly used by weightlifters. Huntington's chorea and anorexic disorders both are characterized by low serum BCAA. These diseases, as well as forms of Parkinson's, may respond to BCAA therapy. BCAA, and particularly leucine, are among the amino acids most essential for muscle health. (http://www.dcnutrition.com); Leucine (abbreviated as Leu or L) is a branched-chain amino acid with the chemical formula HO2CCH(NH2)CH2CH(CH3)2. Leucine is classified as a hydrophobic amino acid due to its aliphatic isobutyl side chain. It is encoded by six codons (UUA, UUG, CUU, CUC, CUA, and CUG) and is a major component of the subunits in ferritin, astacin and other 'buffer' proteins. Leucine is an essential amino acid. Leucine is a branched-chain amino acid (BCAA) since it possesses an aliphatic side-chain that is non-linear.

Propiophenone substituted at the beta-carbon by an amino group." []

Gamma-Caprolactone, also known as 4-ethyl-4-butanolide or 4-hexanolide, belongs to the class of organic compounds known as gamma butyrolactones. Gamma butyrolactones are compounds containing a gamma butyrolactone moiety, which consists of an aliphatic five-member ring with four carbon atoms, one oxygen atom, and bears a ketone group on the carbon adjacent to the oxygen atom. Thus, Gamma-caprolactone is considered to be a fatty ester lipid molecule. Gamma-Caprolactone is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Gamma-Caprolactone exists in all eukaryotes, ranging from yeast to humans. Outside of the human body, Gamma-caprolactone has been detected, but not quantified in several different foods, such as potato, cereals and cereal products, pomes, alcoholic beverages, and fruits. It is occasionally found as a volatile component of human urine. In some cases differences up to an order of magnitude are observed. It has been also found in the polar fraction of human blood.

6-Methyl indole is a member of indoles.

N-methylhydantoin is a imidazolidine-2,4-dione that is the N-methyl-derivative of hydantoin. It has a role as a bacterial metabolite. It derives from a hydantoin. N-Methylhydantoin is a small molecular weight polar substance, the product of degradation of creatinine by bacteria (hydrolyzed by creatinine iminohydrolase, EC 3.5.4.21 to ammonia and N-methylhydantoin). In mammals, the metabolism of 1-methylhydantoin occurs via 5-hydroxy-1-methylhydantoin. In a reported human case, 1-Methylhydantoin was found as an unexpected metabolite of the intelligence-affecting substance dupracetam (PMID:15533691, 8287520, 3196760, 7294979).

A D-alpha-amino acid zwitterion arising from the transfer of a proton from the carboxy to the amino group of D-leucine; major species at pH 7.3." []

A beta-alanine derivative arising from quaternisation of the nitrogen of beta-alanine with three methyl groups and removal of the proton attached to the carboxy group. It is an osmoprotective compound accumulated by most members of the highly stress-tolerant Plumbaginaceae family." []

6-Deoxyfagomine is an alkaloid from the roots of Lycium chinense (Chinese boxthorn).

2-hydroxycyclohexan-1-one is a secondary alpha-hydroxy ketone and a hydroxycyclohexanone. 2-Hydroxycyclohexan-1-one is a natural product found in Phaseolus vulgaris with data available.