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. 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 it has a flowery smell and is a constituent of many flower scents (such as orange blossoms) and perfumes.