What is an Indole?

Christina Hall

An indole is an organic heterocyclic compound with a bicyclic structure having a nitrogen-composed pyyrole ring fused to a benzene ring; any product that contains these indolic structures is considered an indole. The compound is aromatic and solid at room temperature, and it has many applications in the fragrance industry, and increasingly, the pharmaceutical industry. Indoles are primarily produced within the human body as a byproduct of the degradation process of the amino acid, tryptophan. It is processed and usually found to accumulate in human feces, and at high concentrations, indoles possess a strong, unpleasant fecal odor. Surprisingly, at very low concentrations, they have a pleasant, flowery smell and are used often as a constituent in flower scents, like orange blossom.

One indole derivative, indole-3-carbinol, can be found in cauliflower.
One indole derivative, indole-3-carbinol, can be found in cauliflower.

Indoles are important precursors for other substances made within the human body and are, therefore, researched and used in lifestyle and medical applications. The compound was officially discovered in 1866 by a scientist working with the properties of zinc dust who reduced oxindole from the zinc dust into an indole. After the discovery, indoles became important constituents of the textile industry, and as more research was conducted, the larger role that indoles played within the human body system was realized. The indolic nucleus in substances like tryptophan and auxin has led to a better understanding of their mechanism within the body.

Indole is found abundantly in cruciferous vegetables like cabbage.
Indole is found abundantly in cruciferous vegetables like cabbage.

The complex chemical structure of indoles make them stabilizing to protein structure. Any structure that contains the compound or its derivative can help an enzyme or protein form into its correct structure or even help to correct the structure. One of the proposed methods of this action is that indoles readily form hydrogen bonds, which are essential for protein formation. Proteins that contain the rings associated with indolic structure stand up to heat and chemical manipulation better than proteins without the rings. Many of the indoles that are harvested today come from coal tar, where it is found in one of its most stable states.

Indole alkaloids are a group of specific chemicals that are found in many plants around the world including snakeroot and periwinkle. One indole derivative, indole-3-carbinol, is found abundantly in cruciferous vegetables like broccoli, cauliflower, and cabbage. The properties of this indole derivative are anti-carcinogenic, antioxidant, and anti-artherogenic. These effects have been well-proven in randomized controlled studies. More research will reveal the many applications that this derivative and others like it will have in the treatment of lifestyle diseases.

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Discussion Comments


@amysamp - I find that the best odor reducers are the ones that claim they have an odor reducer and a fragrance on top of it. I think the odor reducer actually does reduce the odor (just doesn't completely eliminate it) and then the additional fragrance covers the reduced odor.

I just learned about the indol as a supplement! I thought I would look up more information before I buy indole 3 carbinol, which I found on a vitamin website. The description said it helped with fighting free radicals.

But now that I know I can get the indole goods in broccoli, cauliflower, and other vegetables, I think I will opt for the food as these vegetables add very few calories to the bottom line of our intake.


How strange that in high concentration an indole smells awful and at low concentrations it smells like flowers?!

I had a friend who was an engineer and one of the biggest projects he had was to come up with the opposite of an indole - he had to come up with something that would make the smell of fecal matter dissipate.

Apparently there was an overpopulated area that needed this technology. Learning about an indole makes me wonder if this was at the core of how he and his team solved the problem.

I think that is what is interesting about the fragrance industry - is that it is not just about smells but also fighting unwanted smells. I have seen so many products that claim to eliminate odors, but yet fail to do so - so if anyone finds one - let me know!

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