Indole acts as a signaling molecule in various biological processes, interacting with specific receptors and enzymes to regulate cell signaling pathways and gene transcription. It modulates bacterial biofilm formation and virulence as well as communication between microorganisms. Indole also demonstrates enzymatic inhibition, antimicrobial and antioxidant effects, and potential therapeutic applications in diabetes management and cancer treatment. It undergoes pyrrole ring cleavage to produce N-formyl-o-aminobenzoic acid.

In vitro, indole exhibits various bioactivities including enzymatic inhibition, antimicrobial effects, and antioxidant properties. It has been studied as a potential α-glucosidase inhibitor. Indole shows moderate lipophilicity with a LogP value of 2.14. It serves as a starting material for the preparation of oxindole, indole-3-carboxaldehyde, and other derivatives. The compound demonstrates antimicrobial activity against various bacterial strains.

In vivo, indole and indole sulfate, as gut bacterial metabolites of tryptophan, can alter arterial blood pressure in rats through peripheral and central mechanisms. Indole has been studied for its effects on various physiological processes. It is naturally present in human feces and has a strong fecal odor. The compound's role as a microbial signaling molecule has implications for host-microbe interactions and overall health.

Indole is used in enzyme inhibition assays, particularly for studying α-glucosidase activity. Cell-free assays typically involve measuring the compound's ability to inhibit specific enzymes using chromogenic or fluorogenic substrates. Receptor binding studies may be performed using purified receptor preparations. Spectrophotometric methods are employed to assess indole's antioxidant capacity through DPPH or ABTS radical scavenging assays.

In vitro cellular assays using indole involve treating various cell lines to assess its biological activities. Cells are cultured in appropriate media at 37°C in 5% CO₂. Indole is tested at various concentrations to evaluate effects on cell viability, enzyme activity, and signaling pathways. MTT assays are used to assess cytotoxicity. Antimicrobial activity is evaluated using bacterial cultures with MIC determination. The compound is typically dissolved in DMSO for cell-based experiments.

In vivo studies of indole are conducted in animal models to evaluate its effects on blood pressure regulation, metabolism, and other physiological functions. Indole is administered orally or intraperitoneally. Endpoints include blood pressure measurements, metabolic parameters, and behavioral assessments. As an endogenous metabolite, indole is also measured in biological samples from animal models of various diseases to understand its role in pathophysiology.

Metabolism / Metabolites
Indole undergoes pyrrole ring cleavage to produce N-formyl-o-aminobenzoic acid, an unstable compound that decomposes into o-aminobenzoic acid and formic acid. Indole is first hydroxylated to produce indolephenol, then indigo, which may undergo a hydrolytic ring-opening reaction. ...Indole is metabolized in rats to produce indolephenol, oxyindole, 5-hydroxyoxyindole, and indigo... 2,2-bis(3-indole)indolephenol is produced in horseradish. Deoxyviolin is produced in Chromobacterium. Cis-6,7-dihydroxy-6,7-dihydroxyindole may be present in Pseudomonas. /Excerpt from Table/ 3,3'-Diindolylacetic acid is produced in peas. o-Formamidobenzaldehyde is produced in scopolamine. 3-Hydroxyindole is produced in cocci. /Excerpt from table/
For more complete data on the metabolism/metabolites of indole (10 in total), please visit the HSDB record page.
Known human metabolites of indole include 6-hydroxyindole, indophenol, and indoleone.
Indole has a molecular weight of 117.15 and molecular formula C₈H₇N. It has moderate lipophilicity with a LogP of 2.14. Indole is a volatile compound with a characteristic odor. It is metabolized through hydroxylation to indoxyl, which is then converted to isatin. The compound is absorbed and distributed in the body, with detectable levels in blood and tissues. Excretion occurs through urine and feces as metabolites.

Indole is classified as a hazardous material and requires special shipping considerations. Acute toxicity data indicate that indole can be harmful if ingested, inhaled, or absorbed through skin. It may cause irritation to eyes, skin, and respiratory tract. Chronic exposure effects are not well-documented. Standard laboratory safety precautions should be followed when handling indole, including use of fume hoods, gloves, and protective clothing.

[1]. Indole as an intercellular signal in microbial communities. FEMS Microbiol Rev. 2010 Jul;34(4):426-44.

1H-Indole is an indole compound and a polycyclic aromatic hydrocarbon. It is a metabolite of Escherichia coli and a tautomer of 3H-indole. Indole is a metabolite found or produced in Escherichia coli (K12 strain, MG1655 strain). Indole has also been reported in Tetrastigma hemsleyanum, Daphne odora, and other organisms with relevant data. Mechanism of Action: This study investigated the effects of heterocyclic compounds on hepatic enzymes that metabolize exogenous substances in mice. Female CD-1 mice were administered 5 μmol/kg coumarin, trimethylene oxide (TMO), or trimethylene sulfide (TMS) by gavage for 6 days; or daily by gavage of benzofuran, indole, or indole-3-methanol (IC) for 10 days. Animals were sacrificed 1 or 2 days after the last administration; livers were removed and the activities of 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), cytochrome c reductase (cyt-c-red), and cytochrome P450 were measured. Except for indole, all compounds significantly enhanced epoxide hydrolase activity. Except for TMO and TMS, all compounds increased GST activity. NADH/QR activity was increased only by coumarin and benzofuran. Indole only enhanced the activities of glutathione S-transferase (GST), uridine diphosphate glucose dehydrogenase (UDPGDH), and cytochrome c reductase. IC enhanced the activities of GST, UDPGDH, cytochrome c reductase, epoxide hydrolase, and cytochrome P450 and its associated monooxygenases. The reactions of benzofuran and coumarin were more diverse. Both compounds enhanced the activities of epoxide hydrolase, GST, and NADH/QR. Benzofuran decreased cytochrome P450 levels and increased cyclooxygenase (ECOD) activity.
Indole is a fundamental heterocyclic compound that serves as the core structure for many biologically active molecules, including the amino acid tryptophan, neurotransmitters serotonin and melatonin, and numerous pharmaceutical drugs. It is used as a starting material in organic synthesis for the preparation of various compounds including gramine, oxindole, and indole-3-carboxaldehyde. Indole is a component of jasmine oil. It is widely used in the chemical and pharmaceutical industries as a building block for drug discovery and development.

C8H7N

117.15

117.057

120-72-9

Indole-d6;104959-27-5;Indole-13C;85597-55-3;Indole-13C8,15N;1337952-53-0;Indole-15N;40167-58-6;Indole-d7;73509-20-3

798

LEAFLETS (WATER, PETROLEUM), CRYSTALS (ETHER)
Colorless to yellowish scales, turning red on exposure to light and air.
WHITE CRYSTALLINE SOLID
Colorless, shiny flakes

1.1±0.1 g/cm3

253.0±9.0 °C at 760 mmHg

51-54 °C(lit.)

107.8±11.3 °C

0.0±0.5 mmHg at 25°C

1.681

2.14

1

0

0

9

101

0

N1([H])C([H])=C([H])C2=C([H])C([H])=C([H])C([H])=C12

SIKJAQJRHWYJAI-UHFFFAOYSA-N

InChI=1S/C8H7N/c1-2-4-8-7(3-1)5-6-9-8/h1-6,9H

1H-indole

AI3 01540; AI3-01540; Indole

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~853.61 mM)
H2O : ~3.57 mg/mL (~30.47 mM)

Solubility in Formulation 1: ≥ 2.75 mg/mL (23.47 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 27.5 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.75 mg/mL (23.47 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 27.5 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.75 mg/mL (23.47 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 27.5 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)