Quinoline

Quinoline, also known as azanaphthalene or benzopyridine, is a colorless to yellowish, highly refractive, hygroscopic liquid with a pungent odor. It was named after the compounds quinine and cinchonine, from which quinoline was originally obtained.

Formally, quinoline is a naphthalene molecule in which one carbon atom of the ring skeleton has been replaced by a nitrogen atom. Quinoline is contained in coal tar and is extracted from it. Quinoline does not occur freely in nature, but is the starting product of many natural substances. These include the quinoline alkaloids, which occur in high concentrations in cinchona bark trees (Cinchona officinalis). To this group belong the china alkaloids with quinine as the best known representative. Quinoline is an important basic substance in the chemical and pharmaceutical industry. Quinoline is used for the production of pharmaceuticals, herbicides and fungicides and as a basic solvent.
The most important quinoline derivatives for the formulation are 8-quinolinol and clioquinol.

The structural isomer of quinoline is isoquinoline, which is internationally known as "isoquinolinium".

Recently, it has become increasingly difficult to obtain the active ingredient in adequate pharmaceutical quality; meanwhile, the substances are practically no longer available.

The finished drug ^Chinosol® is also off the market, so that alternatives to quinolinol preparations have to be considered.