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Indole

PubChem CID
798
Structure
Indole_small.png
Indole_3D_Structure.png
Indole__Crystal_Structure.png
Molecular Formula
Synonyms
  • indole
  • 1H-Indole
  • 120-72-9
  • 2,3-Benzopyrrole
  • Indol
Molecular Weight
117.15 g/mol
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Dates
  • Create:
    2004-09-16
  • Modify:
    2025-01-11
Description
1H-indole is an indole and a polycyclic heteroarene. It has a role as an Escherichia coli metabolite. It is a tautomer of a 3H-indole.
Indole is a metabolite found in or produced by Escherichia coli (strain K12, MG1655).
Indole has been reported in Tetrastigma hemsleyanum, Daphne odora, and other organisms with data available.

1 Structures

1.1 2D Structure

Chemical Structure Depiction
Indole.png

1.2 3D Conformer

1.3 Crystal Structures

1 of 3
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COD Number
Associated Article
Thierry Maris. Indole in Pnma at 100 K. Personal communication to COD 2020;:-.
Crystal Structure Depiction
Crystal Structure Depiction
Hermann-Mauguin space group symbol
P n m a
Hall space group symbol
-P 2ac 2n
Space group number
62
a
7.6434 Å
b
14.6714 Å
c
5.5496 Å
α
90 °
β
90 °
γ
90 °
Z
4
Z'
0.5
Residual factor
0.0317

2 Names and Identifiers

2.1 Computed Descriptors

2.1.1 IUPAC Name

1H-indole
Computed by Lexichem TK 2.7.0 (PubChem release 2021.10.14)

2.1.2 InChI

InChI=1S/C8H7N/c1-2-4-8-7(3-1)5-6-9-8/h1-6,9H
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.3 InChIKey

SIKJAQJRHWYJAI-UHFFFAOYSA-N
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.4 SMILES

C1=CC=C2C(=C1)C=CN2
Computed by OEChem 2.3.0 (PubChem release 2024.12.12)

2.2 Molecular Formula

C8H7N
Computed by PubChem 2.2 (PubChem release 2021.10.14)

2.3 Other Identifiers

2.3.1 CAS

120-72-9

2.3.3 European Community (EC) Number

2.3.4 UNII

2.3.5 ChEBI ID

2.3.6 ChEMBL ID

2.3.7 DrugBank ID

2.3.8 DSSTox Substance ID

2.3.9 FEMA Number

2.3.10 HMDB ID

2.3.11 JECFA Number

1301

2.3.12 KEGG ID

2.3.13 Metabolomics Workbench ID

2.3.14 NCI Thesaurus Code

2.3.15 Nikkaji Number

2.3.16 NSC Number

2.3.17 Wikidata

2.3.18 Wikipedia

2.4 Synonyms

2.4.1 MeSH Entry Terms

  • indole
  • indole hydrochloride
  • indole, 14C-labeled

2.4.2 Depositor-Supplied Synonyms

3 Chemical and Physical Properties

3.1 Computed Properties

Property Name
Molecular Weight
Property Value
117.15 g/mol
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
XLogP3
Property Value
2.1
Reference
Computed by XLogP3 3.0 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Donor Count
Property Value
1
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Acceptor Count
Property Value
0
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Rotatable Bond Count
Property Value
0
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Exact Mass
Property Value
117.057849228 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Monoisotopic Mass
Property Value
117.057849228 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Topological Polar Surface Area
Property Value
15.8 Ų
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Heavy Atom Count
Property Value
9
Reference
Computed by PubChem
Property Name
Formal Charge
Property Value
0
Reference
Computed by PubChem
Property Name
Complexity
Property Value
101
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Isotope Atom Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Atom Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Undefined Atom Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Undefined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Covalently-Bonded Unit Count
Property Value
1
Reference
Computed by PubChem
Property Name
Compound Is Canonicalized
Property Value
Yes
Reference
Computed by PubChem (release 2021.10.14)

3.2 Experimental Properties

3.2.1 Physical Description

White to yellowish solid with an unpleasant odor; Pleasant odor in dilute solutions; Turns red when exposed to light or air; [Hawley] White or yellow crystalline powder; [MSDSonline]
Solid
White lustrous, flakey crystalline solid; Unpleasant odour at high concentration, odour becomes floral at higher dilutions

3.2.2 Color / Form

LEAFLETS (WATER, PETROLEUM), CRYSTALS (ETHER)
Weast, R.C. (ed.). Handbook of Chemistry and Physics. 57th ed. Cleveland: CRC Press Inc., 1976., p. C-349
Colorless to yellowish scales, turning red on exposure to light and air.
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993, p. 634
WHITE CRYSTALLINE SOLID
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 270
Colorless, shiny flakes
Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. VA14 167

3.2.3 Odor

ALMOST FLORAL ODOR WHEN HIGHLY PURIFIED, OTHERWISE EXHIBITS CHARACTERISTIC ODOR OF FECES
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 271
Unpleasant odor in high concentration but pleasant in dilute solution.
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993, p. 634
Light jasmine odor
Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. VA14 167

3.2.4 Boiling Point

254 °C
PhysProp
253 °C @ 762 mm Hg; 128-133 °C @ 28 mm Hg
Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 851
253.00 to 254.00 °C. @ 760.00 mm Hg
The Good Scents Company Information System

3.2.5 Melting Point

52.5 °C
PhysProp
52 °C
Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 851
Heat of Formation= 1.5660X10+8 J/kmol; Heat of Fusion at the Melting Point= 9.0000X10+6 J/kmol
Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.
52.5 °C

3.2.6 Solubility

3560 mg/L (at 25 °C)
YALKOWSKY,SH & DANNENFELSER,RM (1992)
SOL IN HOT WATER, HOT ALC, ETHER, BENZENE
Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 851
1 G IN 2 ML OF 70% ALC
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 270
SOL IN TOLUENE
Weast, R.C. (ed.). Handbook of Chemistry and Physics. 57th ed. Cleveland: CRC Press Inc., 1976., p. C-349
Soluble in fixed oils; insoluble in mineral oil and glycerol.
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993, p. 634
For more Solubility (Complete) data for INDOLE (6 total), please visit the HSDB record page.
3.56 mg/mL
Soluble in fixed oils and propylene glycol; Insoluble in glycerol
Soluble (in ethanol)

3.2.7 Density

1.22 g/cu m at 25 °C
Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 76th ed. Boca Raton, FL: CRC Press Inc., 1995-1996., p. 3-200

3.2.8 Vapor Pressure

0.01 [mmHg]
0.0122 mm Hg at 25 °C
Yaws CL; Handbook of Vapor Pressure. Volume 3. C8 to C28 Compounds. Gulf Publishing Co.: Houston, TX (1994)

3.2.9 LogP

2.14
HANSCH,C ET AL. (1995)
Log P= 2.14
Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 38
2.14
HANSCH,C ET AL. (1995)

3.2.10 LogS

-1.52
ADME Research, USCD

3.2.11 Stability / Shelf Life

NOT VERY STABLE ON EXPOSURE TO LIGHT (TURNS RED)
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 270

3.2.12 Heat of Combustion

3.650 kJ/kg at 25 °C
Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. VA14 167

3.2.13 Dissociation Constants

pKa (basic)= -2.4
Adler TK, Albert A; J Med Chem 6: 480-3 (1963)

3.2.14 Collision Cross Section

121 Ų [M+H]+ [CCS Type: DT; Method: single field calibrated with Agilent tune mix (Agilent)]

117.08 Ų [M-H]- [CCS Type: DT; Method: single field calibrated with Agilent tune mix (Agilent)]

3.2.15 Kovats Retention Index

Standard non-polar
1265 , 1276 , 1244.3 , 1257 , 1305 , 1263 , 1273 , 1291 , 1303 , 1255.9 , 1281.1 , 1260 , 1263 , 1273 , 1274 , 1276 , 1296 , 1310 , 1255 , 1255 , 1279 , 1292 , 1298 , 1298 , 1278 , 1255 , 1256 , 1260 , 1304 , 1277 , 1248 , 1276 , 1282 , 1269 , 1267.2 , 1260 , 1260 , 1271.1 , 1304 , 1270.4 , 1275.2 , 1265.4 , 1264 , 1265 , 1248 , 1266.1 , 1250 , 1304 , 1277 , 1304 , 1276 , 1248 , 1276 , 1292.6
Semi-standard non-polar
1289 , 1320 , 1287 , 1319 , 1288 , 1288 , 1288 , 1295 , 1295 , 1290 , 1290 , 1300 , 1288 , 1293 , 1291 , 1294 , 1288 , 1328 , 1329 , 1340 , 1295 , 1292 , 1292 , 1293 , 1297 , 1292 , 1294 , 1289 , 1299 , 1300 , 1303 , 1287 , 1290 , 1298 , 1297 , 1316 , 1251 , 1289 , 1340 , 1297 , 1254 , 1293 , 1293 , 1282 , 1300 , 1320 , 1297 , 1295 , 1288 , 1303 , 1303 , 1290 , 1301 , 1283 , 1307 , 1307 , 1329.6 , 1283 , 1288 , 1288 , 1301 , 1293 , 1310 , 1327 , 1295.9 , 1305 , 1304 , 1303 , 1301 , 1287 , 1289 , 1294 , 1296 , 1296 , 1288 , 1305 , 1286 , 1270 , 1292 , 1328 , 1329 , 1340 , 1299.6 , 1303 , 1290.8 , 219.3 , 220.8 , 222.66 , 205.26
Standard polar
2420 , 2405 , 2446 , 2444 , 2456 , 2412 , 2444 , 2444 , 2465 , 2445 , 2444 , 2441 , 2435 , 2435 , 2444 , 2446 , 2449 , 2420 , 2426 , 2471 , 2454 , 2455 , 2455 , 2471 , 2451 , 2476 , 2414 , 2471 , 2463 , 2450 , 2445.4 , 2436 , 2448 , 2451 , 2431 , 2444 , 2475 , 2478 , 2460 , 2444 , 2450 , 2463 , 2403.9 , 2465 , 2398 , 2404.3 , 2443.2

3.2.16 Other Experimental Properties

CONGEALING POINT: MORE THAN 51 °C (AFTER BEING DRIED OVER SULFURIC ACID)
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 270
Enthalpy of vaporization= 597.5 kJ/kg from 10.3 to 27.4 °C
Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. VA14 167
hydroxyl radical rate constant = 1.54X10-10 cu-cm/molc sec @ 25 °C
Atkinson R; Journal of Physical And Chemical Reference Data. Monograph No 1 (1989)

3.3 SpringerMaterials Properties

3.4 Chemical Classes

Nitrogen Compounds -> Indoles
Waste-water effluent contaminant

3.4.1 Drugs

Pharmaceuticals -> Listed in ZINC15
S55 | ZINC15PHARMA | Pharmaceuticals from ZINC15 | DOI:10.5281/zenodo.3247749

3.4.2 Food Additives

FLAVORING AGENT OR ADJUVANT -> FDA Substance added to food

3.4.3 Fragrances

Fragrance Ingredient (Indole) -> IFRA transparency List

4 Spectral Information

4.1 1D NMR Spectra

1 of 2
1D NMR Spectra
NMR: 473 (Sadtler Research Laboratories Spectral Collection)
2 of 2
1D NMR Spectra

4.1.1 1H NMR Spectra

1 of 5
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Spectra ID
Instrument Type
Varian
Frequency
500 MHz
Solvent
Water
pH
7.00
Shifts [ppm]:Intensity
7.13:43.59, 7.14:100.00, 6.58:68.83, 7.53:93.86, 7.22:51.82, 7.13:43.05, 7.22:53.45, 7.16:61.76, 7.71:85.77, 7.69:89.64, 7.24:90.72, 6.59:71.36, 7.16:62.12, 7.25:44.35, 7.55:83.89, 7.25:45.14
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Spectra ID
Instrument Type
JEOL
Frequency
400 MHz
Solvent
CDCl3
Shifts [ppm]:Intensity
7.16:484.00, 7.18:704.00, 7.29:311.00, 7.05:955.00, 7.05:984.00, 7.12:551.00, 7.28:336.00, 7.65:376.00, 7.81:116.00, 7.12:905.00, 6.53:618.00, 7.63:405.00, 7.10:430.00, 7.18:836.00, 7.06:814.00, 6.52:1000.00, 6.51:565.00, 7.63:684.00, 6.52:686.00, 7.20:434.00, 7.26:463.00, 6.52:662.00, 6.53:661.00, 7.10:450.00, 7.63:705.00, 6.51:616.00, 7.27:935.00, 7.65:666.00, 7.29:621.00, 7.18:353.00, 7.65:683.00, 7.66:376.00, 7.04:794.00, 7.29:606.00, 7.16:518.00, 7.27:462.00, 7.26:946.00, 7.11:753.00, 7.63:711.00, 7.13:783.00, 7.14:775.00, 7.20:465.00
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4.1.2 13C NMR Spectra

1 of 4
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Spectra ID
Instrument Type
Varian
Frequency
25.16 MHz
Solvent
CDCl3
Shifts [ppm]:Intensity
111.10:826.00, 119.74:881.00, 102.22:841.00, 120.63:841.00, 121.85:1000.00, 127.73:423.00, 135.65:294.00, 124.26:622.00
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Spectra ID
Instrument Type
Bruker
Solvent
CDCl3
Shifts [ppm]:Intensity
124.15:54.02, 135.76:7.49, 127.83:10.45, 121.99:79.90, 119.82:69.21, 111.04:64.01, 120.74:68.78, 102.60:68.61
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4.1.3 15N NMR Spectra

1 of 2
Copyright
Copyright © 2016-2024 W. Robien, Inst. of Org. Chem., Univ. of Vienna. All Rights Reserved.
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2 of 2
Copyright
Copyright © 2016-2024 W. Robien, Inst. of Org. Chem., Univ. of Vienna. All Rights Reserved.
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4.2 2D NMR Spectra

4.2.1 1H-1H NMR Spectra

2D NMR Spectra Type
1H-1H TOCSY
Spectra ID
Shifts [ppm] (F2:F1)
7.17:6.55, 7.65:7.66, 7.36:7.36, 7.65:7.21, 7.17:7.16, 7.19:7.10, 7.21:7.21, 7.19:7.38, 7.65:7.17, 7.12:7.64, 7.20:7.66, 7.37:7.13, 8.06:8.05, 7.12:7.14, 7.37:7.37, 6.55:6.55, 7.12:7.12, 7.65:7.12, 7.37:7.21, 7.65:7.19, 7.37:7.10, 7.19:7.64, 7.17:8.05, 6.55:7.16, 7.37:7.12, 7.19:7.12, 7.65:7.64, 7.65:7.36, 8.06:6.55, 7.12:7.36, 7.12:7.38, 7.37:7.64, 6.55:8.05, 7.65:7.38, 7.12:7.19, 8.06:7.16, 7.12:7.10, 7.37:7.66, 7.37:7.19, 7.65:7.10, 7.65:7.14, 7.20:7.19, 7.12:7.66, 7.19:7.36, 7.19:7.14, 7.37:7.17
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4.2.2 1H-13C NMR Spectra

2D NMR Spectra Type
1H-13C HSQC
Spectra ID
Instrument Type
Bruker
Frequency
600 MHz
Solvent
Water
pH
7.00
Shifts [ppm] (F2:F1):Intensity
7.71:123.17:0.53, 7.40:128.62:1.00, 6.59:103.76:0.67, 7.15:122.25:0.58, 7.55:114.37:0.40, 7.25:124.34:0.47
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4.3 Mass Spectrometry

4.3.1 GC-MS

1 of 15
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Spectra ID
Instrument Type
EI-B
Ionization Mode
positive
Top 5 Peaks

117.0 99.99

89.0 20.50

118.0 9

63.0 8.30

116.0 7.80

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Notes
instrument=MX-1303
2 of 15
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Spectra ID
Instrument Type
EI-B
Ionization Mode
positive
Top 5 Peaks

117.0 99.99

89.0 25.50

63.0 15

28.0 11

39.0 9.80

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Notes
instrument=Unknown

4.3.2 MS-MS

1 of 6
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Spectra ID
Ionization Mode
Positive
Top 5 Peaks

118.065 100

91.0542 24.95

117.0574 3.07

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Spectra ID
Ionization Mode
Positive
Top 5 Peaks

118.06487 100

91.0532 29.60

72.07959 6.40

117.06973 4.30

100.12448 2.70

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4.3.3 LC-MS

1 of 5
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Authors
Matsuda F, Suzuki M, Sawada Y, Plant Science Center, RIKEN.
Instrument
UPLC Q-Tof Premier, Waters
Instrument Type
LC-ESI-QTOF
MS Level
MS2
Ionization Mode
POSITIVE
Ionization
ESI
Collision Energy
Ramp 5-60 V
Fragmentation Mode
LOW-ENERGY CID
Precursor m/z
118.06565
Precursor Adduct
[M+H]+
Top 5 Peaks

118.0657 999

118.0949 85

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License
CC BY-SA
2 of 5
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Authors
Matsuda F, Suzuki M, Sawada Y, Plant Science Center, RIKEN.
Instrument
Q-Tof Premier, Waters
Instrument Type
LC-ESI-QTOF
MS Level
MS2
Ionization Mode
POSITIVE
Ionization
ESI
Collision Energy
Ramp 5-45 V
Precursor m/z
118.06565
Top 5 Peaks

118.0657 999

118.0949 85

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License
CC BY-NC

4.3.4 Other MS

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Other MS
MASS: 442 (Atlas of Mass Spectral Data, John Wiley & Sons, New York)
2 of 7
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Authors
SASAKI S, TOYOHASHI UNIV. OF TECH.
Instrument
MX-1303
Instrument Type
EI-B
MS Level
MS
Ionization Mode
POSITIVE
Ionization
ENERGY 50 eV
Top 5 Peaks

117 999

89 205

118 90

63 83

116 78

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License
CC BY-NC-SA

4.4 UV Spectra

MAX ABSORPTION (ALCOHOL): 218 NM (LOG E= 4.44); 271 NM (LOG E= 3.79); 287 NM (LOG E= 3.66)
Weast, R.C. (ed.). Handbook of Chemistry and Physics. 57th ed. Cleveland: CRC Press Inc., 1976., p. C-349
UV: 1269 (Sadtler Research Laboratories Spectral Collection)
Weast, R.C. and M.J. Astle. CRC Handbook of Data on Organic Compounds. Volumes I and II. Boca Raton, FL: CRC Press Inc. 1985., p. V1 773

4.5 IR Spectra

IR Spectra
IR: 415 (Sadtler Research Laboratories IR Grating Collection)

4.5.1 FTIR Spectra

1 of 2
Technique
CAPILLARY CELL: MELT
Source of Sample
Aldrich Chemical Company, Inc., Milwaukee, Wisconsin
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
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2 of 2
Instrument Name
Bruker Tensor 27 FT-IR
Technique
Film (Dichloromethane)
Source of Spectrum
Bio-Rad Laboratories, Inc.
Source of Sample
Alfa Aesar, Thermo Fisher Scientific
Catalog Number
A14427
Lot Number
10182235
Copyright
Copyright © 2016-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.5.2 ATR-IR Spectra

1 of 2
Instrument Name
Bio-Rad FTS
Technique
ATR-Neat (DuraSamplIR II)
Source of Spectrum
Forensic Spectral Research
Source of Sample
Sigma-Aldrich Inc.
Catalog Number
I3408
Lot Number
01525HJ
Copyright
Copyright © 2012-2024 John Wiley & Sons, Inc. All Rights Reserved.
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2 of 2
Instrument Name
Bruker Tensor 27 FT-IR
Technique
ATR-Neat (DuraSamplIR II)
Source of Spectrum
Bio-Rad Laboratories, Inc.
Source of Sample
Alfa Aesar, Thermo Fisher Scientific
Catalog Number
A14427
Lot Number
10182235
Copyright
Copyright © 2016-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.5.3 Near IR Spectra

1 of 2
Instrument Name
BRUKER IFS 88
Technique
NIR Spectrometer= INSTRUMENT PARAMETERS=INST=BRUKER,RSN=21007,REO=2,CNM=HEI,ZFF=2
Source of Spectrum
Prof. Buback, University of Goettingen, Germany
Copyright
Copyright © 1989, 1990-2024 Wiley-VCH Verlag GmbH & Co. KGaA. All Rights Reserved.
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Instrument Name
BRUKER IFS 88
Technique
NIR Spectrometer= INSTRUMENT PARAMETERS=INST=BRUKER,RSN=21007,REO=2,CNM=HEI,ZFF=2
Source of Spectrum
Prof. Buback, University of Goettingen, Germany
Copyright
Copyright © 1989, 1990-2024 Wiley-VCH Verlag GmbH & Co. KGaA. All Rights Reserved.
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4.5.4 Vapor Phase IR Spectra

1 of 2
Instrument Name
DIGILAB FTS-14
Technique
Vapor Phase
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
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2 of 2
Technique
Vapor Phase
Source of Spectrum
Sigma-Aldrich Co. LLC.
Source of Sample
Aldrich
Catalog Number
I3408
Copyright
Copyright © 2018-2024 Sigma-Aldrich Co. LLC. - Database Compilation Copyright © 2018-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.6 Raman Spectra

1 of 2
Technique
FT-Raman
Source of Spectrum
Forensic Spectral Research
Source of Sample
Sigma-Aldrich Inc.
Catalog Number
I3408
Lot Number
01525HJ
Copyright
Copyright © 2012-2024 John Wiley & Sons, Inc. All Rights Reserved.
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2 of 2
Instrument Name
Bruker MultiRAM Stand Alone FT-Raman Spectrometer
Technique
FT-Raman
Source of Spectrum
Bio-Rad Laboratories, Inc.
Source of Sample
Alfa Aesar, Thermo Fisher Scientific
Catalog Number
A14427
Lot Number
10182235
Copyright
Copyright © 2016-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.7 Other Spectra

SADTLER REF NUMBER: 4586 (IR, PRISM)
Weast, R.C. (ed.). Handbook of Chemistry and Physics. 57th ed. Cleveland: CRC Press Inc., 1976., p. C-349
Intense mass spectral peaks: 117 m/z (100%), 90 m/z (33%), 89 m/z (21%), 118 m/z (9%)
Hites, R.A. Handbook of Mass Spectra of Environmental Contaminants. Boca Raton, FL: CRC Press Inc., 1985., p. 26
Intense mass spectral peaks: 63 m/z
Pfleger, K., H. Maurer and A. Weber. Mass Spectral and GC Data of Drugs, Poisons and their Metabolites. Parts I and II. Mass Spectra Indexes. Weinheim, Federal Republic of Germany. 1985., p. 147

6 Chemical Vendors

7 Drug and Medication Information

7.1 FDA National Drug Code Directory

7.2 Biomarker Information

8 Food Additives and Ingredients

8.1 Food Additive Classes

Flavoring Agents
JECFA Functional Classes
Flavouring Agent -> FLAVOURING_AGENT;

8.2 FEMA Flavor Profile

Burnt, Mothball

8.3 FDA Substances Added to Food

Substance
Used for (Technical Effect)
FLAVORING AGENT OR ADJUVANT
Document Number (21 eCFR)
FEMA Number
2593
GRAS Number
3, 25
JECFA Flavor Number
1301

8.4 Evaluations of the Joint FAO / WHO Expert Committee on Food Additives - JECFA

1 of 5
Chemical Name
1-BENZAZOLE
Evaluation Year
2004
ADI
No safety concern at current levels of intake when used as a flavouring agent
Tox Monograph
2 of 5
Chemical Name
BENZOPYRROLE
Evaluation Year
2004
ADI
No safety concern at current levels of intake when used as a flavouring agent
Tox Monograph
3 of 5
Chemical Name
1-BENZO(b)PYRROLE
Evaluation Year
2004
ADI
No safety concern at current levels of intake when used as a flavouring agent
Tox Monograph
4 of 5
Chemical Name
2,3-BENZOPYRROLE
Evaluation Year
2004
ADI
No safety concern at current levels of intake when used as a flavouring agent
Tox Monograph
5 of 5
Chemical Name
INDOLE
Evaluation Year
2004
ADI
No safety concern at current levels of intake when used as a flavouring agent
Tox Monograph

9 Pharmacology and Biochemistry

9.1 Metabolism / Metabolites

INDOLE UNDERGOES SCISSION OF PYRROLE RING TO YIELD N-FORMYLANTHRANILIC ACID, AN UNSTABLE COMPD WHICH DECOMP INTO ANTHRANILIC ACID & FORMIC ACID. INDOLE IS FIRST HYDROXYLATED TO GIVE INDOXYL & THEN ISATIN, & IT IS PROBABLY LATTER WHICH UNDERGOES HYDROLYTIC RING OPENING.
Parke, D. V. The Biochemistry of Foreign Compounds. Oxford: Pergamon Press, 1968., p. 69
...INDOLE IS METABOLIZED BY RAT TO INDOXYL, OXINDOLE, 5-HYDROXYOXINDOLE & ISATIN...
Parke, D. V. The Biochemistry of Foreign Compounds. Oxford: Pergamon Press, 1968., p. 45
YIELDS 2,2-BIS(3-INDOLYL)INDOXYL IN HORSERADISH. DEOXYVIOLACEIN IN CHROMOBACTERIUM. CIS-6,7-DIHYDRO-6,7-DIHYDROXYINDOLE PROBABLY IN PSEUDOMONAS. /FROM TABLE/
Goodwin, B.L. Handbook of Intermediary Metabolism of Aromatic Compounds. New York: Wiley, 1976., p. I-2
YIELDS 3,3'-DIINDOLYLACETIC ACID IN PEA. O-FORMAMIDOBENZALDEHYDE IN TECOMA. 3-HYDROXYOXINDOLE IN COCCUS. /FROM TABLE/
Goodwin, B.L. Handbook of Intermediary Metabolism of Aromatic Compounds. New York: Wiley, 1976., p. I-3
For more Metabolism/Metabolites (Complete) data for INDOLE (10 total), please visit the HSDB record page.
Indole has known human metabolites that include Indoxyl, 6-Hydroxyindole, and Oxindole.
S73 | METXBIODB | Metabolite Reaction Database from BioTransformer | DOI:10.5281/zenodo.4056560

9.2 Mechanism of Action

The effects of heterocyclic cmpd on hepatic xenobiotic metabolizing enzymes were studied in mice. Female CD-1 mice were admin 5 u mol/kg coumarin, trimethylene oxide (TMO), or trimethylene sulfide (TMS) for 6 days by gavage, or benzofuran, indole, or indole-3-carbinol (IC) daily for 10 days. Animals were /sacrificed/ 1 or 2 days after the last dose; livers were removed and assayed for epoxide hydrolase, glutathione-S-transferase (GST), reduced NADH-quinone-reductase (NADH/QR), glucose-6-phosphate-dehydrogenase (G6PDH), glutathione-reductase (GSSG-red), uridine-diphosphate-glucose-dehydrogenase (UDPGDH), aniline-hydroxylase, 7-ethoxycoumarin-deethylase (ECOD), and cytochrome-c-reductase (cyt-c-red) activities, and cytochrome p450. All cmpd except indole, significantly enhanced epoxide hydrolase activity. GST activities were elevated by all cmpd except TMO and TMS. NADH/QR activity was incr only by coumarin and benzofuran. Indole incr only GST, UDPGDH and cyt-c-red activities. IC enhanced GST, UDPGDH, cyt-c-red, epoxide hydrolase and cytochrome p450 and related monooxygenase activities. Benzofuran and coumarin showed more varied responses. Both cmpd incr epoxide hydrolase, GST and NADH/QR activities. Benzofuran decr cytochrome p450 content and elevated ECOD activity.
Heine HS et al; Chemico-Biol Interact 59 (2): 219-30 (1986)

9.3 Human Metabolite Information

9.3.1 Tissue Locations

  • Epidermis
  • Fibroblasts
  • Intestine
  • Neuron

9.3.2 Cellular Locations

Membrane

9.4 Biochemical Reactions

9.5 Transformations

10 Use and Manufacturing

10.1 Uses

EPA CPDat Chemical and Product Categories
The Chemical and Products Database, a resource for exposure-relevant data on chemicals in consumer products, Scientific Data, volume 5, Article number: 180125 (2018), DOI:10.1038/sdata.2018.125
Sources/Uses
Found in feces, neroli oil, jasmine oil, orange-blossom oil, certain flowers, tobacco smoke, and coal tar; Used in perfumery, flavoring, and as chemical reagent, intermediate, and feedstock; [HSDB]
USED IN PERFUMERY
Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 851
SYNTHETIC FLAVOR
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 270
Chemical reagent
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993, p. 634
Used as a chemical intermediate for the synthesis of indol-3-ylacetic acid; 4-indol-3-ylbutyric acid; L-tryptophan.
Ashford, R.D. Ashford's Dictionary of Industrial Chemicals. London, England: Wavelength Publications Ltd., 1994., p. 497
For more Uses (Complete) data for INDOLE (6 total), please visit the HSDB record page.

10.1.1 Use Classification

Food additives -> Flavoring Agents
Fragrance Ingredients
Flavouring Agent -> FLAVOURING_AGENT; -> JECFA Functional Classes
Flavoring Agents -> JECFA Flavorings Index

10.1.2 Household Products

Household & Commercial/Institutional Products

Information on 1 consumer products that contain Indole in the following categories is provided:

• Inside the Home

10.2 Methods of Manufacturing

PREPN FROM O-FORMOTOLUIDE: TYSON, ORG SYN COLL VOL III, 479 (1955); BY DEHYDROCYCLIZING ORTHO ALKYL ANILINES: ERNER ET AL, US PATENT 2,953,575 (1960 TO HOUDRY PROCESS); FROM N-(2-TOLYL)-N'-METHYL-N'-PHENYLFORMAMIDINE: LORENZ ET AL, J ORG CHEM 30, 2531 (1965).
Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 851
OBTAINED FROM 240-260 °C FRACTION FROM COAL TAR: WEISSGERBER, CHEMISCHE BERICHTE 43, 3520 (1910); FROM FECES: BERGEIM, J BIOL CHEM 32, 17 (1917).
Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 851
CAN BE PREPARED ALSO BY REDN OF INDOXYL, INDOXYL CARBOXYLIC ACID, OR INDIGO.
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 270
INDOLE IS PRODUCED BY CONDENSING ANILINE WITH BENZOIN IN THE PRESENCE OF ZINC CHLORIDE
Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984., p. V2 312
For more Methods of Manufacturing (Complete) data for INDOLE (6 total), please visit the HSDB record page.

10.3 Formulations / Preparations

FOUND IN NEROLI OIL IN TRACE QUANTITIES /approx 0.1%/
Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984., p. V16 325
CONSTITUTES 2.5% OF JASMINE OIL
Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984., p. V13 213
Technical, CP, FCC
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993, p. 634

10.4 U.S. Production

(1986) No Data

10.5 U.S. Imports

(1984) 9.92X10+6 g
BUREAU OF THE CENSUS. U.S. IMPORTS FOR CONSUMPTION AND GENERAL IMPORTS 1984 p.1-327

10.6 U.S. Exports

(1986) No Data

10.7 General Manufacturing Information

EPA TSCA Commercial Activity Status
1H-Indole: ACTIVE
REPORTED USES: NON-ALCOHOLIC BEVERAGE 0.26 PPM, ICE CREAMS, ICES, ETC 0.28 PPM; CANDY 0.50 PPM, BAKED GOODS 0.58 PPM, GELATINS & PUDDINGS 0.02-0.40 PPM.
Fenaroli's Handbook of Flavor Ingredients. Volume 2. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975., p. 270
FEMA NUMBER 2593
Furia, T.E. (ed.). CRC Handbook of Food Additives. 2nd ed. Cleveland: The Chemical Rubber Co., 1972., p. 870
Adult corn rootworms are attracted strongly to a variety of kairomones, including indole...
Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. VA14 311

11 Identification

11.1 Analytic Laboratory Methods

SIMULTANEOUS GAS CHROMATOGRAPHIC ANALYSIS OF LOWER FATTY ACIDS, PHENOLS AND INDOLES USING A GLASS CAPILLARY COLUMN.
HOSHIKA Y; SIMULTANEOUS GAS CHROMATOGRAPHIC ANALYSIS OF LOWER FATTY ACIDS, PHENOLS AND INDOLES USING A GLASS CAPILLARY COLUMN; J CHROMATOGR 144(2) 18-190 (1977)
GAS, THIN LAYER & COLUMN CHROMATOGRAPHY WERE USED TO DETERMINE INDOLE IN FRESH MANURE & ANAEROBIC PIT LIQUOR EXTRACTS.
TRAVIS TA, ELLIOTT LF; J ENVIRON QUAL 6(4) 407-410 (1977)
INDOLES & CARBAZOLES WERE ISOLATED FROM CIGARET SMOKE CONDENSATE BY 4-STEP PROCEDURE WHICH INVOLVED EXTRACTION WITH WATER, SILICIC ACID CHROMATOGRAPHY, GEL FILTRATION CHROMATOGRAPHY & GAS CHROMATOGRAPHY.
SNOOK ET AL; ANAL CHEM 50(1) 88-90 (1978)
A COLLABORATIVE STUDY OF GAS-LIQUID CHROMATOGRAPHIC DETERMINATION OF INDOLE IN SHRIMP.
STARUSZKIEWICZ WF JR; COLLABORATIVE STUDY OF GAS-LIQUID CHROMATOGRAPHIC DETERMINATION OF INDOLE IN SHRIMP; J ASSOC OFF ANAL CHIM 57(4) 813-8 (1974)
For more Analytic Laboratory Methods (Complete) data for INDOLE (12 total), please visit the HSDB record page.

11.2 Clinical Laboratory Methods

THE DETECTION, IDENTIFICATION AND MEASUREMENT OF INDOLE, TRYPTAMINE AND 2-PHENETHYLAMINE IN PUTREFYING HUMAN TISSUE. DETERMINATIVE PROCEDURES: GAS CHROMATOGRAPHY, SPECTRAL, & MASS SPECTRAL METHODS.
OLIVER JS, SMITH H, WILLIAMS DJ; THE DETECTION, IDENTIFICATION AND MEASUREMENT OF INDOLE, TRYPTAMINE AND 2-PHENETHYLAMINE IN PUTREFYING HUMAN TISSUE; FORENSIC SCI 9(3) 195-203 (1977)

12 Safety and Hazards

12.1 Hazards Identification

12.1.1 GHS Classification

1 of 2
View All
Pictogram(s)
Corrosive
Acute Toxic
Irritant
Signal
Danger
GHS Hazard Statements

H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral]

H311 (99.1%): Toxic in contact with skin [Danger Acute toxicity, dermal]

H318 (10.7%): Causes serious eye damage [Danger Serious eye damage/eye irritation]

Precautionary Statement Codes

P262, P264, P264+P265, P270, P280, P301+P317, P302+P352, P305+P354+P338, P316, P317, P321, P330, P361+P364, P405, and P501

(The corresponding statement to each P-code can be found at the GHS Classification page.)

ECHA C&L Notifications Summary

Aggregated GHS information provided per 1976 reports by companies from 21 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown.

12.1.2 Hazard Classes and Categories

Acute Tox. 4 (100%)

Acute Tox. 3 (99.1%)

Eye Dam. 1 (10.7%)

Acute toxicity (Oral) - Category 4

Acute toxicity (Dermal) - Category 3

Serious eye damage/eye irritation - Category 2A

Hazardous to the aquatic environment (Acute) - Category 1

12.1.3 Hazards Summary

External application to rabbit eyes scored 8 on a scale of 1-10 (10 being most severe) for degree of injury after 24 hours; [HSDB] Safe when used as a flavoring agent in food; [JECFA] A severe eye irritant; [RTECS]

12.2 Accidental Release Measures

12.2.1 Disposal Methods

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

12.3 Regulatory Information

The Australian Inventory of Industrial Chemicals
Chemical: 1H-Indole
REACH Registered Substance
New Zealand EPA Inventory of Chemical Status
1H-Indole: Does not have an individual approval but may be used under an appropriate group standard

12.4 Other Safety Information

Chemical Assessment
Evaluation - Chemicals that are unlikely to require further regulation to manage risks to environment

13 Toxicity

13.1 Toxicological Information

13.1.1 USGS Health-Based Screening Levels for Evaluating Water-Quality

Chemical
Indole
Chemical Classes
Waste-water effluent contaminant
Reference
Smith, C.D. and Nowell, L.H., 2024. Health-Based Screening Levels for evaluating water-quality data (3rd ed.). DOI:10.5066/F71C1TWP

13.1.2 Acute Effects

13.1.3 Interactions

POSITIVE INOTROPIC EFFECTS OF INDOLE ON ISOLATED GUINEA PIG ATRIA WAS ANTAGONIZED BY PROPRANOLOL & PRETREATMENT WITH RESERPINE.
ZETLER G; NAUNYN-SCHMIEDEBERG'S ARCH PHARMACOL 283 (2): 165-79 (1974)

13.1.4 Non-Human Toxicity Excerpts

...INDOLE...ENHANCE/S/ INCIDENCE OF BLADDER CANCER IN CERTAIN...DEFINED SITUATIONS. ...RATS FED 2-FAA IN DIET WITH...0.8 OR 1.6% INDOLE...DEVELOPED BLADDER TUMORS WHEREAS THOSE FED 2-FAA ALONE DID NOT. ... IN HAMSTERS, INDOLE...& 2-FAA /2-ACETYLAMINOFLUORENE/ GAVE SLIGHTLY MORE BLADDER TUMORS THAN DID 2-FAA BY ITSELF.
Searle, C. E. (ed.). Chemical Carcinogens. ACS Monograph 173. Washington, DC: American Chemical Society, 1976., p. 130
INDOLE INDUCED POSITIVE INOTROPIC EFFECTS IN ISOLATED ATRIA OF GUINEA PIGS.
ETLER G; NAUNYN-SCHMIEDEBERG'S ARCH PHARMACOL 283 (2): 165-79 (1974)
WHEN APPLIED @ CONCN OF 2.5 & 10 MUMOLE WITH OR WITHOUT 6-BENZYLAMINOPURINE TO CULTURES, INDOLE STIMULATED GROWTH OF BOTH NORMAL & TUMOROUS TISSUE.
BEAUCHESNE G; PHYSIOL PLANT 31 (3): 189-92 (1974)
ADDITION OF INDOLE TO DIET CONTAINING 2-ACETYLAMINOFLUORENE PRODUCED INCR IN INCIDENCE OF BLADDER TUMORS IN HAMSTERS OF BOTH SEXES. INCIDENCE WAS HIGHER IN MALES THAN IN FEMALES IRRESPECTIVE OF DIET ADMIN.
MATSUMOTO ET AL; INVEST UROL 14(3) 206-9 (1976)
For more Non-Human Toxicity Excerpts (Complete) data for INDOLE (7 total), please visit the HSDB record page.

13.2 Ecological Information

13.2.1 Environmental Fate / Exposure Summary

Indole's production and use as a chemical intermediate, a perfume fixative, a synthetic flavor and possibly as a kairomone (a volatile chemical released by a plant to attract phytophagus insects) may result in its release to the environment through various waste streams. Indole is released directly to the environment as a component of tobacco smoke and occurs naturally in coal tar, jasmine oil and orange-blossom oil. If released to the atmosphere, indole will mainly exist in the vapor phase based on a experimental vapor pressure of 0.0122 mm Hg at 25 °C. Vapor-phase indole is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals, nitrate radicals, and ozone with estimated half-lives of about 2 to 3 hours, < 1 minute, and 6 hours, respectively. An estimated Koc of 350 and a measured Koc of 187, for a synthetic soil, suggest that indole will have moderate mobility in soil. Volatilization from moist soil surfaces is not expected based on an estimated Henry's Law constant of 5.3X10-7 atm-cu m/mole. Indole is expected to readily biodegrade under both aerobic and anaerobic conditions in soil and water. Indole, added to Chernozem soil at 1 g/kg soil, was completely biodegraded in 19 days. It was completely biodegraded by suspensions of an organic soil under methanogenic and denitrifying conditions within 67 and 144 days, respectively; oxindole was reported as a metabolite of this process. Complete metabolism of indole by methanogenic sediments occurred within 33 days. In water, indole may adsorb to suspended matter in the water column based on its Koc value. Indole should not volatilize from water surfaces based on its Henry's Law constant. Bioconcentration in aquatic organisms should be low given an estimated BCF value of 25. Occupational exposure may occur through inhalation or dermal contact at workplaces where indole is produced or used. The general population will be exposed to indole via inhalation of ambient air, inhalation of tobacco smoke, ingestion of food, and dermal contact with vapors, food, perfumes and other products containing indole. (SRC)

13.2.2 Natural Pollution Sources

Indole is found as a component of jasmine oil and orange-blossom oil(1).
(1) Collin G, Hoke H; Ullmann's Encyclopedia Industrial Chemistry. NY,NY: VCH Publ VA14: 167-70 (1989)

13.2.3 Artificial Pollution Sources

Indole's production and use as a chemical intermediate(1,2), a perfume fixative(2), a synthetic flavor(3) and its possible use as a kairomone (a volatile chemical released by a plant to attract phytophagus insects - used for insect control of adult rootworms)(4) may result in its release to the environment through various waste streams(SRC). Indole is released directly to the environment as a component of tobacco smoke(5). High-temperature coal tar contains on average just under 0.2% indole(6).
(1) Lewis RJ; Hawley's Condensed Chemical Dictionary. 12th ed. NY,NY: Van Nostrand Reinhold Co. p. 634 (1991)
(2) Ashford RD; Ashford's Dictionary of Industrial Chemicals: Properties, Production, Uses. London, England: Wavelength Publ, Ltd. p. 497 (1994)
(3) Furia TE, Bellanca N; Fenaroli's Handbook of Flavor Ingredients. Vol 2. 2nd ed. Cleveland, OH: The Chemical Rubber Co., p. 270 (1975)
(4) Metcalf RL; Ullmann's Encyclopedia Industrial Chemistry. NY,NY: VCH Publ VA14: 311 (1989)
(5) Atkinson R et al; Atmos Environ 29: 3423-32 (1995)
(6) Collin G, Hoke H; Ullmann's Encyclopedia Industrial Chemistry. NY,NY: VCH Publ VA14: 167-70 (1989)

13.2.4 Environmental Fate

TERRESTRIAL FATE: Based on a recommended classification scheme(1), an estimated Koc value of 350(SRC), determined from a measured log Kow(2) and a recommended regression-derived equation(3), and a measured Koc of 187 from a synthetic soil with 0-2% added humic acid(4), indicate that indole will have moderate mobility in soil(SRC). Volatilization of indole should not be important from moist soil surfaces(SRC) given an estimated Henry's Law constant of 5.3X10-7 atm-cu m/mole(SRC), calculated from experimental values for vapor pressure(5) and water solubility(6). Indole is expected to readily biodegrade under both aerobic and anaerobic conditions in soil(SRC). Indole, added to Chernozem soil at 1 and 10 g/kg soil, was completely biodegraded in 19 and 135 days, respectively(7). Indole was completely biodegraded by suspensions of an organic soil (Carlisle muck) under methanogenic and denitrifying conditions within 67 and 144 days, respectively; oxindole was reported as a metabolite of this process(8).
(1) Swann RL et al; Res Rev 85: 23 (1983)
(2) Hansch C et al; Exploring QSAR. Hydrophobic, Electronic, and Steric Constants. ACS Prof Ref Book. Amer Chem Soc, Washington, DC. p. 38 (1995)
(3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 4-9 (1990)
(4) Rebhun M et al; Water Res 26: 79-84 (1992)
(5) Yaws CL; Handbook of Vapor Pressure. Vol 3. C8 to C28 Compounds. Houston, TX: Gulf Publishing Co (1994)
(6) Yalkowsky SH, Dannenfelser RM; Aquasol Database of Aqueous Solubility. Version 5. College of Pharmacy, University of Arizona - Tucson, AZ. PC Version (1992)
(7) Medvedev VA et al; pp. 210-5 in Decomposition of Toxic and Nontoxic Organic Compounds in Soil. Overcash, MR (ed). Ann Arbor, MI: Ann Arbor Sci Publ (1981)
(8) Madsen EL et al; Appl Environ Microbiol 54: 74-78 (1988)
AQUATIC FATE: Based on a recommended classification scheme(1), an estimated Koc value of 350(SRC), determined from a measured log Kow(2) and a recommended regression-derived equation(1), and a measured Koc value of 187(3) indicate that indole may adsorb to suspended solids and sediment in water(SRC). Indole is not expected to volatilize from water surfaces(1,SRC) based on an estimated Henry's Law constant of 5.3X10-7 atm-cu m/mole(SRC), calculated from experimental values for vapor pressure(4) and water solubility(5). According to a classification scheme(6), an estimated BCF value of 25(1,SRC), from a measured log Kow(2), suggests that bioconcentration in aquatic organisms is low(SRC). Indole is expected to readily biodegrade under both aerobic and anaerobic conditions in water(SRC). At 10 °C, aerobic groundwater containing a mixture of aromatic compounds completely biodegraded indole in 310 hours, including an acclimation period of 130 hours(7). Complete metabolism of indole by methanogenic sediments from the shore, edge, and bottom of Buffalo Run stream, PA, occurred within 33 days; oxindole was formed during this process(8). Indole was completely biodegraded under denitrifying conditions in 7 days using a sewage inoculum(8).
(1) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 4-9, 5-4, 5-10, 15-1 to 15-29 (1990)
(2) Hansch C et al; Exploring QSAR. Hydrophobic, Electronic, and Steric Constants. ACS Prof Ref Book. Amer Chem Soc, Washington, DC. p. 38 (1995)
(3) Rebhun M et al; Water Res 26: 79-84 (1992)
(4) Yaws CL; Handbook of Vapor Pressure. Volume 3. C8 to C28 Compounds. Houston, TX: Gulf Publ Co (1994)
(5) Yalkowsky SH, Dannenfelser RM; Aquasol Database of Aqueous Solubility. Ver 5. College of Pharmacy, University of Arizona - Tucson, AZ. PC Ver (1992)
(6) Franke C et al; Chemosphere 29: 1501-14 (1994)
(7) Arvin E et al; Inter Conf Physiochemical Biol Detoxif Hazard Wastes 2: 828-47 (1989)
(8) Madsen EL et al; Appl Environ Microbiol 54: 74-78 (1988)
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), indole, which has a measured vapor pressure of 0.0122 mm Hg at 25 °C(2), will exist solely as a vapor in the ambient atmosphere. Vapor-phase indole is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals, nitrate radicals, and ozone(SRC); the half-lives for these reactions in air are estimated to be about 2 to 3 hours, < 1 minute, and 6 hours, respectively(3,SRC).
(1) Bidleman TF; Environ Sci Technol 22: 361-367 (1988)
(2) Yaws CL; Handbook of Vapor Pressure. Vol 3. C8 to C28 Compounds. Houston, TX: Gulf Publ Co (1994)
(3) Atkinson R et al; Atmos Environ 29: 3423-32 (1995)

13.2.5 Environmental Biodegradation

Groundwater containing a mixture of aromatic hydrocarbons and aromatic nitrogen-, sulfur-, and oxygen-containing heterocyclics, including indole initially present at 0.2 to 1 mg/l, gave an aerobic degradation time (defined as the total time from the start of the experiment until a concn less than 1 ug/l is reached) for indole of 310 hours including an acclimation time of 130 hours at 10 °C(1). Indole, in a 5 day BOD test, reached 49.5% of the theoretical BOD using a mixed microbial inoculum obtained from an enrichment culture(2). A 5 day BOD test gave a BOD of 2.07 g/g for indole using a sewage inoculum(3). First order biodegradation rate constants of 4.3X10-2 BOD/hr and 7.7X10-2 spec/hr were measured for indole at 1.6, 2.5, and 3.2 mg/l for a BOD and a UV spectrophotometry detection method, respectively; the inoculum used was a mixed culture obtained from an enrichment culture technique(3). A reaction pathway for the aerobic biodegradation of indole was proposed: indole to indoxyl to dihydroxyindole to isatin to formylanthranilic acid to anthranilic acid to catechol(5). Indole, added to Chernozem soil at 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 g/kg soil, was completely biodegraded in 19, 37, 62, 72, 84, 92, 102, 131, and 135 days, respectively(6).
(1) Arvin E et al; Inter Conf Physiochemical Biol Detoxif Hazard Wastes 2: 828-47 (1989)
(2) Babeu L, Vaishnav DD; J Indust Microbiol 2: 107-15 (1987)
(3) Heukelekian H, Rand MC; J Water Pollut Contr Assoc 24: 1040-53 (1955)
(4) Vaishnav DD, Korthals ET; J Indust Microbiol 8: 209-12 (1991)
(5) Subramanian V et al; Indian Inst Sci J 60: 143-78 (1978)
(6) Medvedev VA et al; pp. 210-5 in Decomposition of Toxic and Nontoxic Organic Compounds in Soil. Overcash, MR (ed). Ann Arbor, MI: Ann Arbor Sci Publ (1981)
Indole was completely biodegraded in 10 days under methanogenic conditions using a 9% anaerobic sewage sludge inoculum forming oxindole as an intermediate metabolite; the concn of indole in the sterile control over this time remained unchanged(1). Throughout the incubation period, net methane production increased, indicating that indole was mineralized(1). Complete metabolism of indole by methanogenic sediments from the shore, edge, and bottom of Buffalo Run stream, PA, occurred within 33 days. As indole disappeared, stoichiometric amounts of oxindole appeared in the sediment suspensions and persisted for over 4 weeks and was completely eliminated over 110 days(2). Complete biodegradation of indole was reported in 24 days using a 9% digested sludge inoculum at 22 °C under methanogenic conditions(2). Indole was completely biodegraded by suspensions of an organic soil (Carlisle muck) under methanogenic conditions within 67 days; concurrently, oxindole appeared, and persisted in near stoichiometric amounts for about 3 weeks(2). No oxindole accumulated under denitrifying conditions, using a soil inoculum, during the 144 days which were required for indole to disappear(2). This pattern was again seen using a 9% sewage sludge inoculum under methanogenic and denitrifying conditions; both conditions required 7 days for complete disappearance of indole; however, oxindole accumulated temporarily in the methanogenic culture but was not seen in the denitrifying culture probably due to rapid metabolism of this compound(2).
(1) Berry DF et al; Appl Environ Microbiol 53: 180-82 (1987)
(2) Madsen EL et al; Appl Environ Microbiol 54: 74-78 (1988)

13.2.6 Environmental Abiotic Degradation

The rate constant for the vapor-phase reaction of indole with photochemically-produced hydroxyl radicals has been measured as 1.54X10-10 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of about 2 to 3 hours at an atmospheric concn of 5X10+5 hydroxyl radicals per cu cm(1,SRC). The main product of this reaction is 2-formylformanilide(1). The rate constant for the vapor-phase reaction of indole with NO3 radicals has been measured as 1.3X10-10 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of < 1 minute at an atmospheric concn of 5X10+8 nitrate radicals per cu cm(1,SRC). The rate constant for the vapor-phase reaction of indole with NO2 radicals has been measured as <2X10-19 cu cm/molecule-sec at 25 °C(1). The rate constant for the vapor-phase reaction of indole with ozone has been measured as 4.9X10-17 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of about 6 hours at an atmospheric concn of 7X10+11 ozone molecules per cu cm(1,SRC). Products of this reaction are 2-formyl-formanilide and 2-aminobenzaldehyde(1). This compound will exist mainly in the unionized form at environmental pH values based on a pKa of - 2.4(2).
(1) Atkinson R et al; Atmos Environ 29: 3423-32 (1995)
(2) Adler TK, Albert A; J Med Chem 6: 480-3 (1963)
Neutral azaarenes are known to be photosensitive(1). At a concn of 3.14 mg/l a half-life of 19 hours was reported for indole in an aqueous coal-oil mixture exposed to sunlight; actinometer-normalized photolysis rate constants of 0.18 and 0.25 /hr were reported for indole in distilled water and an aqueous coal-oil mixture, respectively(1).
(1) Picel KC et al; in ACS Symp Ser, Zika RG, Cooper WJ (ed). Washington, DC: ACS 327(Photochemicstry of Environmental Aquatic Systems): 44-60 (1987)

13.2.7 Environmental Bioconcentration

An estimated BCF value of 25 was calculated for indole(SRC), using a measured log Kow of 2.14(1) and a recommended regression-derived equation(2). According to a classification scheme(3), this BCF value suggests that bioconcentration in aquatic organisms is low(SRC).
(1) Hansch C et al; Exploring QSAR. Hydrophobic, Electronic, and Steric Constants. ACS Prof Ref Book. Amer Chem Soc, Washington, DC. p. 38 (1995)
(2) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 5-4, 5-10 (1990)
(3) Franke C et al; Chemosphere 29: 1501-14 (1994)

13.2.8 Soil Adsorption / Mobility

A Koc of 187 was measured for indole on a synthetic soil consisting of 88-90% sand, 10% clay and 0-2% humic acid(1). The Koc of indole is estimated as approximately 350(SRC), using a measured log Kow of 2.14(2) and a regression-derived equation(3,SRC). According to a recommended classification scheme(4), these Koc values suggest that indole has moderate mobility in soil(SRC).
(1) Rebhun M et al; Water Res 26: 79-84 (1992)
(2) Hansch C et al; Exploring QSAR. Hydrophobic, Electronic, and Steric Constants. ACS Prof Ref Book. Amer Chem Soc, Washington, DC. p. 6 (1995)
(3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 4-9 (1990)
(4) Swann RL et al; Res Rev 85: 23 (1983)

13.2.9 Volatilization from Water / Soil

The Henry's Law constant for indole is estimated as 5.3X10-7 atm-cu m/mole(SRC) from its experimental values for vapor pressure, 0.0122 mm Hg(1), and water solubility, 3560 mg/l(2). This value indicates that indole will be essentially nonvolatile from water surfaces(3,SRC). Indole's Henry's Law constant(1,2,SRC) indicates that volatilization from moist soil surfaces should not occur(SRC).
(1) Yaws CL; Handbook of Vapor Pressure. Volume 3. C8 to C28 Compounds. HOuston,TX: Gulf Publ Co (1994)
(2) Yalkowsky SH, Dannenfelser RM; Aquasol Database of Aqueous Solubility. Ver 5. College of Pharmacy, University of Arizona - Tucson, AZ. PC Ver (1992)
(3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 15-1 to 15-29 (1990)

13.2.10 Environmental Water Concentrations

SURFACE WATER: 1 of 204 surface water samples collected near heavily industrialized areas across the US contained indole at an unreported location and concn(1). Water samples collected from the Adige River, Italy in the Trento province during 1989, contained indole at concns of <10 to 600 ug/l(2).
(1) Ewing BB et al; Monitoring to Detect Previously Unrecognized Pollutants in Surface Waters. Appendix: Organic Analysis Data. USEPA-560/6-77-015 (Appendix: USEPA-560/6-77-015a). Washington, DC: USEPA (1977)
(2) Benfenati E et al; Chemosphere 25: 1665-74 (1992)

13.2.11 Effluent Concentrations

Indole was detected in industrial wastewaters from the following industries: timber products, leather tanning, iron and steel manufacturing, inorganics and plastics, synfuels, and publicly owned treatment works(1). Process water derived from the Fischer Assay retorting of oil shale from Rundle, Australia contained indole at 3 mg/l(2). A grab sample of final effluent from the Addison, IL publicly-owned treatment works in April 1980 contained indole at unreported concns(3). Wastewater obtained during the gasification of Indian Head lignite contained indole at an estimated concn of 1 mg/l(4). Wastewater and sludge from the Iona Island Sewage Treatment plant, Vancouver, British Columbia contained indole at unreported concns(5).
(1) Bursey JT, Pellizzari ED; Analysis of Industrial Wastewater for Organic Pollutants in Consent Decree Survey p. 97 USEPA contract No. 68-03-2867 (1982)
(2) Dobson KR et al; Water Res 19: 849-56 (1985)
(3) Ellis DD et al; Arch Environ Contam Toxicol 11: 373-82 (1982)
(4) Giabbai MF et al; Intern J Environ Anal Chem 20: 113-29 (1985)
(5) Rogers IH et al; Water Pollut Res J Canada 21: 187-204 (1986)
Untreated coke plant wastewater contained indole from 23 to 26,000 ug/l(1). Volatile components in poultry manure contained indole at concns of 5.08 and 10.4 mg/kg(2). Indole was identified in creosote oil extracts at 7700 ug/g(3). Basin floodwater, taken from Fort Devens, MA, following primary treatment, contained indole at 11 ug/l(4,5). Chlorinated still bottom extract contained indole at unreported concns(6).
(1) Monteith H; In: Fluctuations of Trace Contaminants in Sewage Treatment Plants; Monograph Series 1, Adv Water Pollut Res Technol; Canadian Assoc Water Pollut Res Control: Burlington Ontario (1987)
(2) Yasuhara A; J Chrom 387: 371-78 (1987)
(3) Krone CA et al; Environ Sci Technol 20: 1144-50 (1986)
(4) Hutchins SR et al; Water Res 18: 1025-36 (1984)
(5) Bedient PB et al; J Environ Engineer 109: 485-500 (1983)
(6) Gurka DF et al; J Chrom Sci 20: 145-54 (1982)

13.2.12 Sediment / Soil Concentrations

Sediments collected from three creosote-contaminated sediment samples from Eagle Harbor, Puget Sound, WA contained indole at concns less than 22 ug/g(1).
(1) Krone CA et al; Environ Sci Technol 20: 1144-50 (1986)

13.2.13 Atmospheric Concentrations

INDOOR AIR: Indoor air from 11% of the sampled private homes in the Chicago, IL area contained indole at unreported concns (n= 36)(1).
(1) Jarke FH et al; Ashrae Trans 87: 153-66 (1981)
URBAN AIR: Both vapor phase and aerosol fractions of urban air contained indole at unreported concns(1). Indole was identified on aerosols collected from the Southern North Atlantic Ocean at a mean concn of 0.18 ng/cu m(2).
(1) Cautreels W, Van Cauwenberghe K; Atmos Environ 12: 1133-41 (1978)
(2) Duce RA et al; Rev Geophys Space Phys 21: 2-202 to 2-233 (1983)

13.2.14 Food Survey Values

Different samples of Beaufort cheese from the French Alps contained indole at unreported concns(1). Indole, at unreported concns, was reported as a volatile flavor compound in fried bacon(2), roasted filbert nuts(3), short-necked clams and corbicula(4), and pork(5). Water-boiled duck meat and duck fat contained indole at 1.72 and 2.28 ppb, wet basis, respectively(6).
(1) Dumont JP, Adda J; J Agric Food Chem 26: 364-67 (1978)
(2) Ho, CT et al; J Agric Food Chem 31: 336-42 (1983)
(3) Kinlin TE et al; J Agric Food Chem 20: 1021-8 (1972)
(4) Kubota K et al; J Agric Food Chem 39: 1127-30 (1991)
(5) Shahidi F et al; CRC Crit Rev Food Sci Nature 24: 141-243 (1986)
(6) Wu, CM, Liou SE; J Agric Food Chem 40: 838-41 (1992)

13.2.15 Plant Concentrations

Volatile compounds identified in Lonicera japonica flowers (Japanese honeysuckle) contained indole at concns of 52, <20, and 87 ug/kg for fresh flowers, flowers after 12 hours, and flowers after 24 hours, respectively(1).
(1) Schlotzhauer WS et al; J Agric Food Chem 44: 206-09 (1996)

13.2.16 Fish / Seafood Concentrations

Three samples of commercial Mytilus edulis (blue mussel), collected near Holbaek, Denmark, contained indole(1).
(1) Rasmussen T et al; Chemosphere 27: 2123-25 (1993)

13.2.17 Probable Routes of Human Exposure

NIOSH (NOES Survey 1981-1983) has statistically estimated that 6445 workers (4359 of these are female) are potentially exposed to indole in the US(1). Occupational exposure may be through inhalation and dermal contact with this compound at workplaces where indole is produced or used(SRC). The general population will be exposed to indole via inhalation of ambient air, inhalation of tobacco smoke, ingestion of food, and dermal contact with vapors, food and other products such as perfumes containing indole.
(1) NIOSH; National Occupational Exposure Survey (NOES) (1983)

13.2.18 Body Burden

4 of 46 human adipose tissue samples, collected in 1982, contained indole (3 in age category 45+, 1 in age category 15-44 years)(1).
(1) Onstot JD et al; Characterization of HRGC/MS Unidentified Peaks From the Broad Scan Analysis of the FY82 NHATS Composites. Volume I. Technical Approach. Volume II. Appendices. MRI Project No8823-A01, Work Assignment No. 23, Midwest Research Inst: USEPA (1987)
PERSONAL AIR: Expired air from control (n= 20), but not prediabetic (n= 14) or diabetic (n= 28) human study populations contained indole at unreported concns(1).
(1) Krotoszynski BK, O'Neill HJ; J Environ Sci Health A17: 855- 83 (1982)

14 Associated Disorders and Diseases

Disease
Nonalcoholic fatty liver disease
References
PubMed: 23454028
Disease
Irritable bowel syndrome
References
Disease
Pervasive developmental disorder not otherwise specified
References
PubMed: 24130822
Disease
Clostridium difficile infection
References
Disease
Perillyl alcohol administration for cancer treatment
References

15 Literature

15.1 Consolidated References

15.2 NLM Curated PubMed Citations

15.3 Springer Nature References

15.4 Thieme References

15.5 Wiley References

15.6 Nature Journal References

15.7 Chemical Co-Occurrences in Literature

15.8 Chemical-Gene Co-Occurrences in Literature

15.9 Chemical-Disease Co-Occurrences in Literature

16 Patents

16.1 Depositor-Supplied Patent Identifiers

16.2 WIPO PATENTSCOPE

16.3 Chemical Co-Occurrences in Patents

16.4 Chemical-Disease Co-Occurrences in Patents

16.5 Chemical-Gene Co-Occurrences in Patents

17 Interactions and Pathways

17.1 Protein Bound 3D Structures

17.1.1 Ligands from Protein Bound 3D Structures

PDBe Ligand Code
PDBe Structure Code
PDBe Conformer

17.2 Chemical-Target Interactions

17.3 Pathways

18 Biological Test Results

18.1 BioAssay Results

19 Taxonomy

The LOTUS Initiative for Open Natural Products Research: frozen dataset union wikidata (with metadata) | DOI:10.5281/zenodo.5794106

20 Classification

20.1 MeSH Tree

20.2 NCI Thesaurus Tree

20.3 ChEBI Ontology

20.4 ChemIDplus

20.5 ChEMBL Target Tree

20.6 UN GHS Classification

20.7 EPA CPDat Classification

20.8 NORMAN Suspect List Exchange Classification

20.9 CCSBase Classification

20.10 EPA DSSTox Classification

20.11 The Natural Products Atlas Classification

20.12 Consumer Product Information Database Classification

20.13 EPA TSCA and CDR Classification

20.14 LOTUS Tree

20.15 EPA Substance Registry Services Tree

20.16 MolGenie Organic Chemistry Ontology

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CONTENTS