I heard a colleague talk today at the MidAtlantic Regional Meeting of the ACS about his work with fluoroquinones. These molecules (which despite their name contain no fluorine) fluoresce, that is they "glow" when exposed to light. The process can be short circuited by binding another molecule, a quencher, to fluoroquinone. The research discussed the quenching behavior of tryptophan. Tryptophan is an amino acid, one of the building blocks of proteins. Structurally, it's an indole; an aromatic six-membered ring fused to a five-membered ring containing a nitrogen forms the core.
Tryptophan is thought to induce sleep - and is often blamed for post-Thanksgiving meal naps. Melatonin, which also play a role in sleep regulation, is also an indole.
The indoles of chemistry get their name from the Latin for indigo, the dye from which the basic indole structure was first isolated. The indolence which some indoles induce has a different etymological root, dolorens - grief or pain.
Prof. Erland Stevens's online medicinal chemistry course
4 hours ago in The Curious Wavefunction