| Names | |
|---|---|
| IUPAC name 2-(5-hydroxy-1H-indol-3-yl)acetaldehyde | |
| Other names 5-Hydroxyindole-acetaldehyde; 5-HIAL; 5-HIAAL; 5-Hydroxytryptaldehyde; 5-Hydroxyindole-3-acetaldehyde; Serotonin aldehyde [1] | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider | |
| KEGG | |
PubChem CID | |
| UNII | |
CompTox Dashboard (EPA) | |
| |
| |
| Properties | |
| C10H9NO2 | |
| Molar mass | 175.18 g/mol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
5-Hydroxyindoleacetaldehyde (5-HIAL), also known as 5-hydroxytryptaldehyde or as serotonin aldehyde, is an inactive metabolite and metabolic intermediate of the monoamine neurotransmitter serotonin (5-hydroxytryptamine; 5-HT). [2] [3] [1]
5-HIAL is formed from serotonin by oxidative deamination via monoamine oxidase (MAO). [2] [3] MAO-mediated deamination is the primary metabolic pathway of serotonin inactivation. [2] Monoamine oxidase A (MAO-A) has about 120-fold higher affinity for serotonin than monoamine oxidase B (MAO-B). [2] In relation to this, MAO-A is the main isozyme of MAO involved in serotonin degradation. [2]
Following its formation, 5-HIAL is metabolized by aldehyde dehydrogenase (ALDH) to form 5-hydroxyindoleacetic acid (5-HIAA). [2] [3] 5-HIAL can also be converted into small amounts of 5-hydroxytryptophol (5-HTOL; also known as 5-hydroxyindolethanol or 5-HIET) by either aldehyde reductase (ALR/ALDR) or alcohol dehydrogenase (ADH). [2] [4] However, brain concentrations of 5-HTOL are only 1 to 5% of those of 5-HIAA. [2] [4]
Use of ethanol (alcohol) can dramatically increase 5-HTOL formation by inhibiting ALDH and enhancing ADH activity. [2] [5] As a result, the ratio of 5-HTOL to 5-HIAA is a sensitive and reliable marker of recent ethanol ingestion and has been suggested for use in clinical and forensic contexts. [2] [5]
Besides oxidative deamination by MAO into 5-HIAL, serotonin can also be conjugated by glucuronidation via glucuronyltransferases, conjugated by sulfation via sulfotransferases, acetylated and then methylated into melatonin (N-acetyl-5-methoxytryptamine) (which occurs mainly in the pineal gland), and converted into certain other metabolites like 5-hydroxyindole thiazoladine carboxylic acid (5-HITCA). [2] However, these secondary metabolic pathways appear to play only a minor role in serotonin metabolism. [2]
5-HIAL has been implicated in producing neurotoxicity and in the development and progression of neurodegenerative diseases. [6] [7] [8]