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Ketoleucine is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. Ketoleucine is both a neurotoxin and a metabotoxin. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of ketoleucine are associated with maple syrup urine disease (MSUD). MSUD is a metabolic disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), leading to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products (ketoacids) in the blood and urine. The symptoms of MSUD often show in infancy and lead to severe brain damage if untreated. MSUD may also present later depending on the severity of the disease. If left untreated in older individuals, during times of metabolic crisis, symptoms of the condition include uncharacteristically inappropriate, extreme, or erratic behaviour and moods, hallucinations, anorexia, weight loss, anemia, diarrhea, vomiting, dehydration, lethargy, oscillating hypertonia and hypotonia, ataxia, seizures, hypoglycemia, ketoacidosis, opisthotonus, pancreatitis, rapid neurological decline, and coma. In maple syrup urine disease, the brain concentration of branched-chain ketoacids can increase 10- to 20-fold. This leads to a depletion of glutamate and a consequent reduction in the concentration of brain glutamine, aspartate, alanine, and other amino acids. The result is a compromise of energy metabolism because of a failure of the malate-aspartate shuttle and a diminished rate of protein synthesis (PMID: 15930465).

2-Ketohexanoic acid is a potent insulin secretagogue (PMID 7045091). 2-Ketohexanoic acid directly inhibits the ATP-sensitive K+ channel (KATP channel) in pancreatic beta-cells (stimulated in isolated mouse islets), but it is unknown whether direct KATP channel inhibition contributes to insulin release by 2-ketohexanoic acid and related alpha-keto acid anions, which are generally believed to act via beta-cell metabolism (PMID 16014804).

Leucylproline is a dipeptide composed of leucine and proline. 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. It is found in urine (PMID: 3782411).

Isoleucylproline is a dipeptide composed of isoleucine and proline. 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. It is found in urine (PMID: 3782411).

A dipeptide formed from L-isoleucine and L-proline residues." []

Methoxamine is only found in individuals that have used or taken this drug. It is an alpha-adrenergic agonist that causes prolonged peripheral vasoconstriction. It has little if any direct effect on the central nervous system. [PubChem]Methoxamine acts through peripheral vasoconstriction by acting as a pure alpha-1 adrenergic receptor agonist, consequently increasing systemic blood pressure (both systolic and diastolic).

Leucyl-proline is a dipeptide.

Pentaethylene glycol is a poly(ethylene glycol).

An indolylmethylglucosinolic acid that is 1-thio-beta-D-glucopyranose having a 2-(1H-indol-3-yl)-N-(sulfooxy)ethanimidoyl group attached to the anomeric sulfur." []

Tyrosyl-Proline is a dipeptide composed of tyrosine and proline. 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.

2-((3,5-Dihydroxyphenyl)amino)acetic acid is an alpha-amino acid.

2-amino-2-(3,5-dihydroxyphenyl)acetic acid is an alpha-amino acid.

A glycine derivative that is L-alpha-phenylglycine substituted at positions 3 and 5 on the phenyl ring by hydroxy groups." []

4-Hydroxycinnamoylagmatine is found in cereals and cereal products. 4-Hydroxycinnamoylagmatine is isolated from barley seedlings.

Paeonia spp

Methyltetrahydrophthalic anhydride is a cyclic dicarboxylic anhydride that is the cyclic anhydride of methyltetrahydrophthalic acid. It has a role as an allergen. It is a cyclic dicarboxylic anhydride and a tetrahydrofurandione.