Quinoline Alkaloids are ultimately synthesized from Tryptophan (or tryptamine) in plants and unusually contain two nitrogens (one inside and one outside the main skeleton).
• Quinoline Alkaloids best-known member is quinine (occurs in considerable amounts in the bark of Cinchona species such as Cinchona pubescens and Cinchona officinalis) which is used to treat Malaria (650mg of quinine sulfate every 8hrs for 3–7 days) and nocturnal leg cramps (200–400mg of quinine sulfate dihydrate/day for a maximum of 5 weeks).
• Cinchona is a genus of flowering plants in the family Rubiaceae, containing at least 23 species of trees and shrubs.
• The most known member with global importance is quinine (extracts used successfully for many years to treat Malaria).
More Quinoline Alkaloids Details
• The main dietary exposure to quinoline Alkaloids is through beverages, where its pleasant bitter taste is a flavouring component of tonic Water, bitter Lemon, and vermouth.
• Quinine exerts physiological effects on skeletal muscles, increasing the tension response and refractory period to a single maximal stimulus delivered to the muscle directly (or through the nerves). The excitability of the motor endplate region decreases so that responses to repetitive nerve stimulation and to acetylcholine are reduced.
• Quinine may produce alarming Respiratory distress and dysphagia in patients with Myasthenia gravis.
• Quinine may enhance the effects of Cardiac Glycosides, muscle relaxants, and Anti-Coagulants.
• Quinoline or benzo[b]pyridine is a nitrogen-rich heterocyclic compound that was First extracted from coal tar by Friedlieb Ferdinand Runge in 1834.
• Quinolines are conveniently prepared from amines through a number of familiar named reactions developed in the period 1880–88. By heating aniline in a mixture of glycerol and Sulfuric acid, quinoline is produced; this reaction is called as the Skraup synthesis.
• Naturally occurring quinoline is released from the thoracic glands of peruvian stick insect (Oreophoetes peruana), playing the role of chemically defense against spiders, cockroaches, ants, and frogs.
• There is a wide range of quinoline-based natural compounds with diverse biological effects.
• Quinine is one of the most well-known antiMalarial agents extracted from the Peruvian Bark cortex (Cinchona spp).
• During World War II, the demand for Anti-malarial drugs led to the clinical trials of some synthesized quinoline-based molecules among which chloroquine showed promising activities.
• Despite the effective treatment of Malaria using quinine and chloroquine, both of them are toxic to the Human Body.
• Mefloquine was synthesized in the 1970s by United States Army to treat Malaria among soldiers, though it showed serious side effects on mental health.
• Resistance today of the Malaria parasite to all three (3) drugs has been observed worldwide and there is need and research for new Anti-malarial treatments.
Functions of Alkaloids (in Plants)
• Alkaloids are nitrogen storage compounds that are involved to protect them from predators, and functioned as growth regulators and substitutes for Minerals (like Potassium and Calcium).
• When predators attack plants, the Alkaloids can interfere the predator’s Nervous System, membrane transport, Protein synthesis and enzyme activity, while under abiotic or biotic Stress Alkaloids can enhance plant Reproductive rates.
• Some of the Alkaloids may also act as herbicide by inhibiting the growth of competing plants.
Functions of Alkaloids (in Humans)
• Alkaloids are importance compounds in the human pharmaceutical industry.
For instance,
• The Alkaloid derived from beta-carboline group such as harmine has been used as Anti-Microbial, Anti-HIV and anti-parasitic.
• The Vinca Alkaloid (vinblastine and vincristine) isolated from Catharanthus roseus, berberine isolated from Coptis spp. and taxol isolated from Taxus bravifolia have been employed as Anti-Cancer drugs for treating Leukemias, Lymphomas, testicular Cancer, Breast Cancer, Lung Cancers and Kaposi’s sarcoma.
Remedies Commonly used for Alkaloid Poisoning
Three (3) remedies commonly used for Alkaloid Poisoning.
• Black Tea
• Cranesbill
• Witch Hazel
Examples of Quinoline Alkaloids
• Angostura Cortex – contain Alkaloids (cusparine) with bitter Digestive tonic actions.
• Blue Cohosh – contain quinolizidine and isoquinoline-types. Anagyrine, baptifoline, magnoflorine, methylcytisine [caulophylline].
• Ganglong – contain an indoloquinoline Alkaloid (Cryptolepine) and quindoline, and the dimers [biscryptolepine, cryptoquindoline, and cryptospirolepine].
• Gulancha – contain furquinolone Alkaloids (Tyramine, Higenamine, N-cis-feruloyltyramine, N-trans-feruloyltyramine, Paprazine, N-trans-caffeoyltyramine).
• Peruvian Bark Cortex – contain Alkaloids (quinine, quinidine) with Anti-malarial, Febrifuge, relieve Muscle Cramps, bitter Digestive Stimulant actions.
• Prickly Ash – contain furoquinoline Alkaloids (gamma-fAgarine and skimmianine from the leaves).
• Rue – contain furquinolone Alkaloids (about 1.4%, including fAgarine, arborinine, skimmianine, and others).
• Zanthoxylum – contain furoquinolines (dictamine, 8-methoxydictamine, skimmianine, 3-dimethylallyl-4-methoxy-2-quinolone).
