| Record Information |
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| Version | 5.0 |
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| Status | Detected and Quantified |
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| Creation Date | 2005-11-16 15:48:42 UTC |
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| Update Date | 2023-02-21 17:15:07 UTC |
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| HMDB ID | HMDB0000738 |
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| Secondary Accession Numbers | |
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| Metabolite Identification |
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| Common Name | Indole |
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| Description | Indole is an aromatic heterocyclic organic compound. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. The participation of the nitrogen lone electron pair in the aromatic ring means that indole is not a base, and it does not behave like a simple amine. Indole is a microbial metabolite and it can be produced by bacteria as a degradation product of the amino acid tryptophan. It occurs naturally in human feces and has an intense fecal smell. At very low concentrations, however, indole has a flowery smell and is a constituent of many flower scents (such as orange blossoms) and perfumes. As a volatile organic compound, indole has been identified as a fecal biomarker of Clostridium difficile infection (PMID: 30986230 ). Natural jasmine oil, used in the perfume industry, contains around 2.5% of indole. Indole also occurs in coal tar. Indole has been found to be produced in a number of bacterial genera including Alcaligenes, Aspergillus, Escherichia, and Pseudomonas (PMID: 23194589 , 2310183 , 9680309 ). Indole plays a role in bacterial biofilm formation, bacterial motility, bacterial virulence, plasmid stability, and antibiotic resistance. It also functions as an intercellular signalling molecule (PMID: 26115989 ). Recently, it was determined that the bacterial membrane-bound histidine sensor kinase (HK) known as CpxA acts as a bacterial indole sensor to facilitate signalling (PMID: 31164470 ). It has been found that decreased indole concentrations in the gut promote bacterial pathogenesis, while increased levels of indole in the gut decrease bacterial virulence gene expression (PMID: 31164470 ). As a result, enteric pathogens sense a gradient of indole concentrations in the gut to migrate to different niches and successfully establish an infection. |
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| Structure | InChI=1S/C8H7N/c1-2-4-8-7(3-1)5-6-9-8/h1-6,9H |
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| Synonyms | | Value | Source |
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| 2,3-Benzopyrrole | ChEBI | | indol | ChEBI | | 1-Azaindene | HMDB | | 1-Benzazole | HMDB | | Benzo[b]pyrrole | HMDB | | Ketole | HMDB | | Indole | HMDB |
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| Chemical Formula | C8H7N |
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| Average Molecular Weight | 117.1479 |
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| Monoisotopic Molecular Weight | 117.057849229 |
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| IUPAC Name | 1H-indole |
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| Traditional Name | indole |
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| CAS Registry Number | 120-72-9 |
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| SMILES | N1C=CC2=C1C=CC=C2 |
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| InChI Identifier | InChI=1S/C8H7N/c1-2-4-8-7(3-1)5-6-9-8/h1-6,9H |
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| InChI Key | SIKJAQJRHWYJAI-UHFFFAOYSA-N |
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| Chemical Taxonomy |
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| Description | Belongs to the class of organic compounds known as indoles. Indoles are compounds containing an indole moiety, which consists of pyrrole ring fused to benzene to form 2,3-benzopyrrole. |
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| Kingdom | Organic compounds |
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| Super Class | Organoheterocyclic compounds |
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| Class | Indoles and derivatives |
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| Sub Class | Indoles |
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| Direct Parent | Indoles |
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| Alternative Parents | |
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| Substituents | - Indole
- Benzenoid
- Heteroaromatic compound
- Pyrrole
- Azacycle
- Organic nitrogen compound
- Organopnictogen compound
- Hydrocarbon derivative
- Organonitrogen compound
- Aromatic heteropolycyclic compound
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| Molecular Framework | Aromatic heteropolycyclic compounds |
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| External Descriptors | |
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| Ontology |
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| Not Available | Not Available |
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| Physical Properties |
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| State | Solid |
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| Experimental Molecular Properties | | Property | Value | Reference |
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| Melting Point | 52.5 °C | Not Available | | Boiling Point | 253.00 to 254.00 °C. @ 760.00 mm Hg | The Good Scents Company Information System | | Water Solubility | 3.56 mg/mL | Not Available | | LogP | 2.14 | HANSCH,C ET AL. (1995) |
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| Experimental Chromatographic Properties | Experimental Collision Cross Sections |
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| Predicted Molecular Properties | |
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| Predicted Chromatographic Properties | Predicted Collision Cross SectionsPredicted Retention Times Underivatized| Chromatographic Method | Retention Time | Reference |
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| Measured using a Waters Acquity ultraperformance liquid chromatography (UPLC) ethylene-bridged hybrid (BEH) C18 column (100 mm × 2.1 mm; 1.7 μmparticle diameter). Predicted by Afia on May 17, 2022. Predicted by Afia on May 17, 2022. | 3.73 minutes | 32390414 | | Predicted by Siyang on May 30, 2022 | 12.5103 minutes | 33406817 | | Predicted by Siyang using ReTip algorithm on June 8, 2022 | 3.52 minutes | 32390414 | | Fem_Long = Waters ACQUITY UPLC HSS T3 C18 with Water:MeOH and 0.1% Formic Acid | 1811.0 seconds | 40023050 | | Fem_Lipids = Ascentis Express C18 with (60:40 water:ACN):(90:10 IPA:ACN) and 10mM NH4COOH + 0.1% Formic Acid | 481.4 seconds | 40023050 | | Life_Old = Waters ACQUITY UPLC BEH C18 with Water:(20:80 acetone:ACN) and 0.1% Formic Acid | 164.0 seconds | 40023050 | | Life_New = RP Waters ACQUITY UPLC HSS T3 C18 with Water:(30:70 MeOH:ACN) and 0.1% Formic Acid | 322.4 seconds | 40023050 | | RIKEN = Waters ACQUITY UPLC BEH C18 with Water:ACN and 0.1% Formic Acid | 310.0 seconds | 40023050 | | Eawag_XBridgeC18 = XBridge C18 3.5u 2.1x50 mm with Water:MeOH and 0.1% Formic Acid | 442.2 seconds | 40023050 | | BfG_NTS_RP1 =Agilent Zorbax Eclipse Plus C18 (2.1 mm x 150 mm, 3.5 um) with Water:ACN and 0.1% Formic Acid | 439.1 seconds | 40023050 | | HILIC_BDD_2 = Merck SeQuant ZIC-HILIC with ACN(0.1% formic acid):water(16 mM ammonium formate) | 277.0 seconds | 40023050 | | UniToyama_Atlantis = RP Waters Atlantis T3 (2.1 x 150 mm, 5 um) with ACN:Water and 0.1% Formic Acid | 983.8 seconds | 40023050 | | BDD_C18 = Hypersil Gold 1.9µm C18 with Water:ACN and 0.1% Formic Acid | 387.2 seconds | 40023050 | | UFZ_Phenomenex = Kinetex Core-Shell C18 2.6 um, 3.0 x 100 mm, Phenomenex with Water:MeOH and 0.1% Formic Acid | 1182.4 seconds | 40023050 | | SNU_RIKEN_POS = Waters ACQUITY UPLC BEH C18 with Water:ACN and 0.1% Formic Acid | 465.9 seconds | 40023050 | | RPMMFDA = Waters ACQUITY UPLC BEH C18 with Water:ACN and 0.1% Formic Acid | 323.1 seconds | 40023050 | | MTBLS87 = Merck SeQuant ZIC-pHILIC column with ACN:Water and :ammonium carbonate | 502.9 seconds | 40023050 | | KI_GIAR_zic_HILIC_pH2_7 = Merck SeQuant ZIC-HILIC with ACN:Water and 0.1% FA | 212.1 seconds | 40023050 | | Meister zic-pHILIC pH9.3 = Merck SeQuant ZIC-pHILIC column with ACN:Water 5mM NH4Ac pH9.3 and 5mM ammonium acetate in water | 62.6 seconds | 40023050 |
Predicted Kovats Retention IndicesUnderivatizedDerivatized| Derivative Name / Structure | SMILES | Kovats RI Value | Column Type | Reference |
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| Indole,1TMS,isomer #1 | C[Si](C)(C)N1C=CC2=CC=CC=C21 | 1424.0 | Semi standard non polar | 33892256 | | Indole,1TMS,isomer #1 | C[Si](C)(C)N1C=CC2=CC=CC=C21 | 1424.2 | Standard non polar | 33892256 | | Indole,1TMS,isomer #1 | C[Si](C)(C)N1C=CC2=CC=CC=C21 | 1720.5 | Standard polar | 33892256 | | Indole,1TBDMS,isomer #1 | CC(C)(C)[Si](C)(C)N1C=CC2=CC=CC=C21 | 1688.3 | Semi standard non polar | 33892256 | | Indole,1TBDMS,isomer #1 | CC(C)(C)[Si](C)(C)N1C=CC2=CC=CC=C21 | 1628.0 | Standard non polar | 33892256 | | Indole,1TBDMS,isomer #1 | CC(C)(C)[Si](C)(C)N1C=CC2=CC=CC=C21 | 1851.5 | Standard polar | 33892256 |
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| Disease References | | Ulcerative colitis |
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- Garner CE, Smith S, de Lacy Costello B, White P, Spencer R, Probert CS, Ratcliffe NM: Volatile organic compounds from feces and their potential for diagnosis of gastrointestinal disease. FASEB J. 2007 Jun;21(8):1675-88. Epub 2007 Feb 21. [PubMed:17314143 ]
- Walton C, Fowler DP, Turner C, Jia W, Whitehead RN, Griffiths L, Dawson C, Waring RH, Ramsden DB, Cole JA, Cauchi M, Bessant C, Hunter JO: Analysis of volatile organic compounds of bacterial origin in chronic gastrointestinal diseases. Inflamm Bowel Dis. 2013 Sep;19(10):2069-78. doi: 10.1097/MIB.0b013e31829a91f6. [PubMed:23867873 ]
- De Preter V, Machiels K, Joossens M, Arijs I, Matthys C, Vermeire S, Rutgeerts P, Verbeke K: Faecal metabolite profiling identifies medium-chain fatty acids as discriminating compounds in IBD. Gut. 2015 Mar;64(3):447-58. doi: 10.1136/gutjnl-2013-306423. Epub 2014 May 8. [PubMed:24811995 ]
- Ahmed I, Greenwood R, Costello B, Ratcliffe N, Probert CS: Investigation of faecal volatile organic metabolites as novel diagnostic biomarkers in inflammatory bowel disease. Aliment Pharmacol Ther. 2016 Mar;43(5):596-611. doi: 10.1111/apt.13522. Epub 2016 Jan 25. [PubMed:26806034 ]
| | Nonalcoholic fatty liver disease |
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- Raman M, Ahmed I, Gillevet PM, Probert CS, Ratcliffe NM, Smith S, Greenwood R, Sikaroodi M, Lam V, Crotty P, Bailey J, Myers RP, Rioux KP: Fecal microbiome and volatile organic compound metabolome in obese humans with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol. 2013 Jul;11(7):868-75.e1-3. doi: 10.1016/j.cgh.2013.02.015. Epub 2013 Feb 27. [PubMed:23454028 ]
| | Celiac disease |
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- Di Cagno R, De Angelis M, De Pasquale I, Ndagijimana M, Vernocchi P, Ricciuti P, Gagliardi F, Laghi L, Crecchio C, Guerzoni ME, Gobbetti M, Francavilla R: Duodenal and faecal microbiota of celiac children: molecular, phenotype and metabolome characterization. BMC Microbiol. 2011 Oct 4;11:219. doi: 10.1186/1471-2180-11-219. [PubMed:21970810 ]
| | Crohn's disease |
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- Walton C, Fowler DP, Turner C, Jia W, Whitehead RN, Griffiths L, Dawson C, Waring RH, Ramsden DB, Cole JA, Cauchi M, Bessant C, Hunter JO: Analysis of volatile organic compounds of bacterial origin in chronic gastrointestinal diseases. Inflamm Bowel Dis. 2013 Sep;19(10):2069-78. doi: 10.1097/MIB.0b013e31829a91f6. [PubMed:23867873 ]
- De Preter V, Machiels K, Joossens M, Arijs I, Matthys C, Vermeire S, Rutgeerts P, Verbeke K: Faecal metabolite profiling identifies medium-chain fatty acids as discriminating compounds in IBD. Gut. 2015 Mar;64(3):447-58. doi: 10.1136/gutjnl-2013-306423. Epub 2014 May 8. [PubMed:24811995 ]
- Ahmed I, Greenwood R, Costello B, Ratcliffe N, Probert CS: Investigation of faecal volatile organic metabolites as novel diagnostic biomarkers in inflammatory bowel disease. Aliment Pharmacol Ther. 2016 Mar;43(5):596-611. doi: 10.1111/apt.13522. Epub 2016 Jan 25. [PubMed:26806034 ]
| | Irritable bowel syndrome |
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- Walton C, Fowler DP, Turner C, Jia W, Whitehead RN, Griffiths L, Dawson C, Waring RH, Ramsden DB, Cole JA, Cauchi M, Bessant C, Hunter JO: Analysis of volatile organic compounds of bacterial origin in chronic gastrointestinal diseases. Inflamm Bowel Dis. 2013 Sep;19(10):2069-78. doi: 10.1097/MIB.0b013e31829a91f6. [PubMed:23867873 ]
| | Autism |
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- De Angelis M, Piccolo M, Vannini L, Siragusa S, De Giacomo A, Serrazzanetti DI, Cristofori F, Guerzoni ME, Gobbetti M, Francavilla R: Fecal microbiota and metabolome of children with autism and pervasive developmental disorder not otherwise specified. PLoS One. 2013 Oct 9;8(10):e76993. doi: 10.1371/journal.pone.0076993. eCollection 2013. [PubMed:24130822 ]
| | Pervasive developmental disorder not otherwise specified |
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- De Angelis M, Piccolo M, Vannini L, Siragusa S, De Giacomo A, Serrazzanetti DI, Cristofori F, Guerzoni ME, Gobbetti M, Francavilla R: Fecal microbiota and metabolome of children with autism and pervasive developmental disorder not otherwise specified. PLoS One. 2013 Oct 9;8(10):e76993. doi: 10.1371/journal.pone.0076993. eCollection 2013. [PubMed:24130822 ]
| | Clostridium difficile infection |
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- Darkoh C, Plants-Paris K, Bishoff D, DuPont HL: Clostridium difficile Modulates the Gut Microbiota by Inducing the Production of Indole, an Interkingdom Signaling and Antimicrobial Molecule. mSystems. 2019 Mar 19;4(2). pii: mSystems00346-18. doi: 10.1128/mSystems.00346-18. eCollection 2019 Mar-Apr. [PubMed:30944877 ]
- Patel M, Fowler D, Sizer J, Walton C: Faecal volatile biomarkers of Clostridium difficile infection. PLoS One. 2019 Apr 15;14(4):e0215256. doi: 10.1371/journal.pone.0215256. eCollection 2019. [PubMed:30986230 ]
| | Perillyl alcohol administration for cancer treatment |
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- Silva CL, Passos M, Camara JS: Solid phase microextraction, mass spectrometry and metabolomic approaches for detection of potential urinary cancer biomarkers--a powerful strategy for breast cancer diagnosis. Talanta. 2012 Jan 30;89:360-8. doi: 10.1016/j.talanta.2011.12.041. Epub 2011 Dec 22. [PubMed:22284503 ]
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