Indole-3-carbaldehyde (I3A), also known as indole-3-aldehyde and 3-formylindole, is a metabolite of dietary L-tryptophan which is synthesized by human gastrointestinal bacteria, particularly species of the Lactobacillus genus.[2][3] I3A is a biologically active metabolite which acts as a receptor agonist at the aryl hydrocarbon receptor in intestinal immune cells, in turn stimulating the production of interleukin-22 which facilitates mucosal reactivity.[4][3][2]
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| Names | |
|---|---|
| IUPAC name
1H-Indole-3-carbaldehyde | |
| Other names
3-Formylindole; Indole-3-carboxaldehyde; Indole-3-aldehyde | |
| Identifiers | |
3D model (JSmol) |
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| 5-21-08-00246 | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.006.969 
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| EC Number |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C9H7NO | |
| Molar mass | 145.161 g·mol−1 |
| Melting point | 198 °C (388 °F; 471 K) |
| Structure | |
| Orthorhombic | |
| Pca21 | |
a = 14.076, b = 5.8059, c = 8.6909[1] | |
Lattice volume (V) |
710.3 |
Formula units (Z) |
4 |
| Hazards | |
| GHS labelling: | |
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| Warning | |
| H315, H319, H335 | |
| P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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)
Tryptophanase-
expressing bacteria
Intestinal
immune cells
Neuroprotectant:
↓Activation of glial cells and astrocytes ↓4-Hydroxy-2-nonenal levels ↓DNA damage –Antioxidant –Inhibits β-amyloid fibril formation
Maintains mucosal reactivity:
↑IL-22 production
Associated with vascular disease:
↑Oxidative stress ↑Smooth muscle cell proliferation ↑Aortic wall thickness and calcification
Associated with chronic kidney disease:
↑Renal dysfunction –Uremic toxin
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Indole-3-carbaldehyde has reactivity typical of aromatic aldehydes. It can is easily oxidized to indole-3-carboxylic acid. It condenses with nitromethane in a Henry reaction to give 3-nitrovinyl indole.
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Indole-3-carbaldehyde has antifungal properties, and partially accounts for the protection from chytridiomycosis seen in amphibian species which carry Janthinobacterium lividum on their skin.[8]
Lactobacillus spp. convert tryptophan to indole-3-aldehyde (I3A) through unidentified enzymes [125]. Clostridium sporogenes convert tryptophan to IPA [6], likely via a tryptophan deaminase. ... IPA also potently scavenges hydroxyl radicals
Production of IPA was shown to be completely dependent on the presence of gut microflora and could be established by colonization with the bacterium Clostridium sporogenes.
[Indole-3-propionic acid (IPA)] has previously been identified in the plasma and cerebrospinal fluid of humans, but its functions are not known. ... In kinetic competition experiments using free radical-trapping agents, the capacity of IPA to scavenge hydroxyl radicals exceeded that of melatonin, an indoleamine considered to be the most potent naturally occurring scavenger of free radicals. In contrast with other antioxidants, IPA was not converted to reactive intermediates with pro-oxidant activity.
