Quinoline alkaloids are naturally occurring

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

s from the group of

alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...

s, which are chemically derived from quinoline. Some quinoline alkaloids show

antiseptic An antiseptic (from Greek ἀντί ''anti'', "against" and σηπτικός ''sēptikos'', "putrefactive") is an antimicrobial substance or compound that is applied to living tissue/skin to reduce the possibility of infection, sepsis, or putre ...

convulsive A convulsion is a medical condition where the body muscles contract and relax rapidly and repeatedly, resulting in uncontrolled shaking. Because epileptic seizures typically include convulsions, the term ''convulsion'' is sometimes used as a s ...

or antineoplastic effects.

Examples

Alkaloids with a quinoline partial structure are widespread and are usually further subdivided according to their occurrence and biogenetic origin. Among the quinoline alkaloids are the cinchona alkaloids

quinine Quinine is a medication used to treat malaria and babesiosis. This includes the treatment of malaria due to ''Plasmodium falciparum'' that is resistant to chloroquine when artesunate is not available. While sometimes used for nocturnal leg cr ...

and

quinidine Quinidine is a class I antiarrhythmic agent, class IA antiarrhythmic agent used to treat heart rhythm disturbances. It is the enantiomer of Antimalarial medication, antimalarial agent quinine, originally derived from the bark of the cinchona tre ...

, which are important due to their therapeutic potential, furthermore cinchonine and cinchonidine, as well as some furoquinoline alkaloids and acridine alkaloids.

Strychnine Strychnine (, , US chiefly ) is a highly toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, or absorbed through the eye ...

and

brucine Brucine, is an alkaloid closely related to strychnine, most commonly found in the ''Strychnos nux-vomica'' tree. Brucine poisoning is rare, since it is usually ingested with strychnine, and strychnine is more toxic than brucine. In synthetic ch ...

, alkaloids of the nux vomica, which have a hydrogenated quinoline system, are also counted among the quinoline alkaloids. Also nitramarine (1-(2-quinolinyl)-β-carboline) belongs to the quinoline alkaloids. File:Chinin.svg, Qinine File:Chinidin.svg, Qinidine File:Cinchonidin.svg,

Cinchonidine Cinchonidine is an alkaloid found in ''Cinchona officinalis ''Cinchona officinalis'' is a South American tree in the family Rubiaceae. It is native to wet montane forests in Colombia, Ecuador, Peru and Bolivia, between 1600–2700 meters ab ...

File:Strychnine2.svg,

Occurrence

The quinoline alkaloids are mainly found in plants, as in

Rutaceae The Rutaceae is a family, commonly known as the rueRUTACEAE
in BoDD – Botanical Derm ...

and

Rubiaceae The Rubiaceae are a family of flowering plants, commonly known as the coffee, madder, or bedstraw family. It consists of terrestrial trees, shrubs, lianas, or herbs that are recognizable by simple, opposite leaves with interpetiolar stipules ...

, but also in microorganisms and animals. Quinoline is furthermore comprised as a partial structure in the redox factor PQQ (

pyrroloquinoline quinone Pyrroloquinoline quinone (PQQ), also called methoxatin'','' is a redox cofactor and antioxidant. Produced by bacteria, it is found in soil and foods such as kiwifruit, as well as human breast milk. Enzymes using PQQ as a redox cofactor are called ...

) and in quinoenzymes.

Biosynthesis

Biogenetically, there are several proven pathways for the formation of the quinoline system in plants.

Tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α- carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...

e as well as

anthranilic acid Anthranilic acid is an aromatic acid with the formula C6H4(NH2)(CO2H) and has a sweetish taste. The molecule consists of a benzene ring, ''ortho''-substituted with a carboxylic acid and an amine. As a result of containing both acidic and basic f ...

can act as a precursor. The second precursor molecule is either a

hemiterpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ar ...

or a

monoterpene Monoterpenes are a class of terpenes that consist of two isoprene units and have the molecular formula C10H16. Monoterpenes may be linear (acyclic) or contain rings (monocyclic and bicyclic). Modified terpenes, such as those containing oxygen funct ...

(e.g.

secologanin Secologanin is a secoiridoid monoterpene synthesized from geranyl pyrophosphate in the mevalonate pathway. Secologanin then proceeds with dopamine or tryptamine to form ipecac and terpene indole alkaloids, respectively. Biosynthesis Secologanin ...

e in cinchona alkaloids).

Literature

* {{RömppOnline, Name=Chinolin-Alkaloide , Datum=26. Juni 2014 , ID=RD-03-01309 Alkaloids