Pharmacognosy with the Basics of Plant Biochemistry - Kovalyov V. M. 2004

Special Part
Alkaloids
Quinoline Alkaloids (Tryptophan Group)

Alkaloids contain a quinoline Skeleton or its derivatives in their molecules. The group comprises over 300 representatives, which are divided into the following subgroups:

simple quinolines (alkyl and aryl quinolines, 2- and 4-quinolones, their alkyl and alkenyl derivatives);

hemiterpene and terpenoid tricyclic derivatives;

furoquinolines;

dimeric compounds that, In addition to quinoline, sometimes contain residues of ß-carboline, quinuclidine (e.g., quinine), etc. Often these are classified into separate groups of alkaloids specific to certain genera, such as cinchona alkaloids.

Various quinoline alkaloids originate from different biogenetic precursors. The Biosynthesis of quinoline alkaloids in the Rutaceae family starts from anthranilic acid. Cinchona alkaloids are most often found alongside indole alkaloids of the Corynanthe type. Thus, their distant precursor is L-Tryptophan.

Quinoline alkaloids exhibit a wide spectrum of pharmacological activity. Most of them have a sedative effect on the Central Nervous system, while some, such as flindersine, show antifeedant properties. Echinopsine and quinine are used in medical practice.

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Echinopsine

Quinine

Echinopsine (N-methyl-4-quinolone) is found in the seeds of plants of the genus *Echinops* (Asteraceae) and acts as a stimulant of the central and peripheral nervous systems.

Quinine is the most important of the cinchona alkaloids, which are specific to species of the genera *Cinchona* and *Remijia* belonging to Water/237.html">The Madder family, Rubiaceae. Four diastereoisomers of quinine are known; all of them have been synthesized.

Quinine is produced from cinchona bark — Cortex Chinae, seu Cortex Cinchonae. The raw material consists of the bark of various species, races, and hybrids of wild and cultivated cinchona trees: *Cinchona succirubra*, *C. calisaya*, *C. ledgeriana*, *C. officinalis*, and *C. robusta*. They are cultivated in Colombia, Ecuador, Peru, and Bolivia.

In the alkaloid mixture, the main components are quinine, quinidine, and their dimethoxy derivatives — cinchonidine and cinchonine. The total alkaloid content in the raw material exceeds 6.5%, of which one-third to two-thirds are quinoline alkaloids. They accumulate in the bark parenchyma, where they are bound to quinic and cinchotannic acids. The content of quinic acid reaches 5–8%. Anthraquinones, which are characteristic of the Rubiaceae family, are represented in the plant bark by tetrahydroxyanthraquinones.

Quinine hydrochloride, quinine dihydrochloride, and quinine sulfate are used as antiprotozoal agents active against all species of malaria plasmodia. Quinidine sulfate is used as an antiarrhythmic agent; tincture and decoction of cinchona bark stimulate appetite and improve Digestion.

In homeopathy, the bark of various cinchona species is used for severe cardiac weakness, drop in Blood pressure, blood hemolysis, Hematuria, dermatitis, and damage to the auditory nerve leading to deafness, and the Optic nerve leading to blindness. The main indication for use is profound weakness resulting from fluid loss: blood, saliva, sweat, gastric juice, etc.