Indole

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. Indole is widely distributed in the natural environment and can be produced by a variety of bacteria. As an intercellular signal molecule, indole regulates various aspects of bacterial physiology, including spore formation, plasmid stability, resistance to drugs, biofilm formation, and virulence. The amino acid tryptophan is an indole derivative and the precursor of the neurotransmitter serotonin.

Chemical Structure and Properties

Indole is a solid at room temperature. It occurs naturally in human feces and has an intense fecal odor. At very low concentrations, however, it has a flowery smell and is a constituent of many flower scents (such as orange blossoms) and perfumes. It also occurs in coal tar.

The structure of indole is very stable and it survives under harsh conditions. The molecule is planar because it is highly aromatic (the lone pair of electrons on the nitrogen atom is delocalized into the pi system, contributing to the aromaticity).

Biological Role and Applications

Indole is a major constituent of the tryptophan molecule, and tryptophan is one of the twenty amino acids that form proteins. Some bacteria can metabolize tryptophan into indole.

In medicine, indole is used primarily as a precursor to the anti-cancer drug indole-3-carbinol and the anti-inflammatory agent indomethacin. Researchers are investigating its use for treating depression, since it is a precursor to serotonin.

See Also

• Tryptophan
• Serotonin
• Indole-3-carbinol
• Indomethacin

References

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