The best studies on quinine with regard to applications, intake and effects.

Analytics of Quinine and its Derivatives.
Kluska M, Marciniuk-Kluska A, Prukała D, Prukała W
Crit Rev Anal Chem. 2016;46(2):139-45. doi: 10.1080/10408347.2014.996700.

Artesunate versus Quinine - keeping our options open.
Frosch AEP.
Clin Infect Dis. 2019 May 2. pii: ciz335. doi: 10.1093/cid/ciz335.

Protective effects of pyrroloquinoline quinine against oxidative stress-induced cellular senescence and inflammation in human renal tubular epithelial cells via Keap1/Nrf2 signaling pathway.
Wang Z, Han N, Zhao K, Li Y, Chi Y, Wang B.
Int Immunopharmacol. 2019 Jul;72:445-453. doi: 10.1016/j.intimp.2019.04.040.

Synthesis and systemic toxicity assessment of quinine-triazole scaffold with antiprotozoal potency.
Sahu A, Agrawal RK, Pandey R.
Bioorg Chem. 2019 Apr 20;88:102939. doi: 10.1016/j.bioorg.2019.102939.

Shape adaptation of quinine in cyclodextrin cavities: NMR studies.
Wójcik J, Ejchart A, Nowakowski M.
Phys Chem Chem Phys. 2019 Mar 27;21(13):6925-6934. doi: 10.1039/c9cp00590k.

Pyrroloquinoline quinine protects HK-2 cells against high glucose-induced oxidative stress and apoptosis through Sirt3 and PI3K/Akt/FoxO3a signaling pathway.
Wang Z, Li Y, Wang Y, Zhao K, Chi Y, Wang B.
Biochem Biophys Res Commun. 2019 Jan 8;508(2):398-404. doi: 10.1016/j.bbrc.2018.11.140. 

Effects of Quinine, Quinidine and Chloroquine on Human Muscle Nicotinic Acetylcholine Receptors.
Gisselmann G, Alisch D, Welbers-Joop B, Hatt H.
Front Pharmacol. 2018 Nov 20;9:1339. doi: 10.3389/fphar.2018.01339. eCollection 2018.

High-level artemisinin-resistance with quinine co-resistance emerges in P. falciparum malaria under in vivo artesunate pressure.
Tyagi RK, Gleeson PJ, Arnold L, Tahar R, Prieur E, Decosterd L, Pérignon JL, Olliaro P, Druilhe P.
BMC Med. 2018 Oct 1;16(1):181. doi: 10.1186/s12916-018-1156-x.

Use of hyperbaric oxygen therapy in quinine-associated visual disturbances.
Laes JR, Hendriksen S, Cole JB.
Undersea Hyperb Med. 2018 Jul-Aug;45(4):457-461.

fMRI-Based Brain Responses to Quinine and Sucrose Gustatory Stimulation for Nutrition Research in the Minipig Model: A Proof-of-Concept Study.
Coquery N, Meurice P, Janvier R, Bobillier E, Quellec S, Fu M, Roura E, Saint-Jalmes H, Val-Laillet D.
Front Behav Neurosci. 2018 Jul 24;12:151. doi: 10.3389/fnbeh.2018.00151. eCollection 2018.

A Case Report of Nephrotic Syndrome While Undergoing Quinine Therapy.
Albrecht B, Giebel S, McCarron M, Prasad B.
Cureus. 2018 Mar 7;10(3):e2283. doi: 10.7759/cureus.2283.

The Role of Quinine-Responsive Taste Receptor Family 2 in Airway Immune Defense and Chronic Rhinosinusitis.
Workman AD, Maina IW, Brooks SG, Kohanski MA, Cowart BJ, Mansfield C, Kennedy DW, Palmer JN, Adappa ND, Reed DR, Lee RJ, Cohen NA.
Front Immunol. 2018 Mar 28;9:624. doi: 10.3389/fimmu.2018.00624. eCollection 2018.

Intragastric quinine administration decreases hedonic eating in healthy women through peptide-mediated gut-brain signaling mechanisms.
Iven J, Biesiekierski JR, Zhao D, Deloose E, O'Daly OG, Depoortere I, Tack J, Van Oudenhove L.
Nutr Neurosci. 2018 Apr 2:1-13. doi: 10.1080/1028415X.2018.1457841.

The best study I have yet met on the indications and contraindications of quinine in bitter drinks, is undoubtedly the one published in 2008 by BfR which is the German Federal Institute for Risk Assessment and was established as a federal authority under the jurisdiction of the Federal Ministry of Food and German agriculture (BmEL). Here is the first part. The study is very long, about 16 pages and contains all the bibliographical references:

Quinine is a bitter-tasting, crystalline white powder. It is obtained from the bark of the cinchona tree and belongs to the group of alkaloids. In medicine quinine is used to treat malaria and nocturnal leg cramps. In the food sector, quinine is used as a flavouring mainly in beverages like bitter lemon and tonic water.

When larger amounts of quinine are consumed, it can constitute a health problem for some consumer groups. BfR sees risks in particular for quinine intakes during pregnancy. For instance, a newborn baby, whose mother had drunk more than 1 litre tonic water a day in the weeks up to its birth, suffered health disorders. Based on existing regulations in the medicinal product sector, BfR, therefore, advises pregnant women against drinking quininecontaining beverages on precautionary grounds. People who have been advised against taking quinine, cinchona bark or their preparations by their doctors because of their clinical pictures should not consume any quinine-containing soft drinks either. This applies, for instance, to people who suffer from tinnitus, pre-existing damage to the optic nerve, haemolytic anaemia or who are hypersensitive to quinine or cinchona alkaloids. Patients with cardiac arrhythmia and people who take medicine that interacts with quinine, should only drink quinine-containing soft drinks after consulting their doctors. This applies in particular to medications which inhibit blood coagulation. At higher levels of tonic water consumption, it may be necessary to reduce their therapeutic dose.

Already today quinine must be mentioned by name in the list of ingredients of quininecontaining products. BfR also believes that there is a need for information which attracts the attention more particularly of pregnant women and other risk groups to possible health impairments. Motor vehicle drivers should be informed that larger amounts of quininecontaining bitter beverages can cause visual disturbances. BfR recommends raising awareness about the possible health risks from quinine to consumers. Specific information should be provided about the symptoms of quinine hypersensitivity and cinchonism (typical adverse reactions to quinine). Consumers should be advised to immediately stop their quinine intake if these symptoms occur, and to consult a doctor.

BfR recommends that the health assessment of quinine by the Scientific Committee on Food from 1988 should be updated.

BfR is of the opinion that the problems of quinine-containing bitter soft drinks underline the importance of the systematic recording of adverse reactions that occur in conjunction with the consumption of foods. The Institute, therefore, explicitly supports the setting up of a central reporting office (1).

References___________________________________________________

(1) Quinine-containing beverages may cause health problems
Updated BfR Health Assessment No 020/2008, 17 February 2005

The name describes the structure of the molecule:

• Quinine is a natural compound found in the bark of the cinchona tree. Quinine has been used for centuries as a treatment for malaria because of its ability to kill disease-causing parasites.
• Hydrochloride refers to the salt form of the hydrochloride of a drug or compound. When a compound is formulated as salt hydrochloride, it can increase its solubility in water, improve its stability and improve its absorption in the body.

What it is for and where

Medical

Quinine hydrochloride is the salt form of quinine hydrochloride, which is still used today as a treatment for malaria. It is typically administered orally, and works by killing malaria parasites in the body.

Food

• Quinine studies

• Molecular Formula: C₂₀H₂₅ClN₂O₂   C₂₀H₂₄N₂O₂ · HCl · 2H₂O 
• Molecular Weight: 360.882 g/mol
• UNII: 7CS0WNO31M
• CAS: 130-89-2  6119-47-7  7549-43-1  11034-23-4  70181-37-2  70181-38-3  918656-55-0
• EC Number: 231-437-7  205-001-1
• FEMA Number: 2976
• PubChem Substance ID 329751012
• MDL number MFCD00151248
• Beilstein Registry Number 6112655

Synonyms:

• (8alpha,9R)-6'-Methoxycinchonan-9-Ol Monohydrochloride
• Quinine HCl
• Quinine hydrochloride
• Cinchonan-9-ol, 6'-methoxy-, hydrochloride, (8alpha,9R)-
• Cinchonan-9-ol, 6'-methoxy-, hydrochloride (1:?), (8alpha,9R)-
• Cinchonan-9-ol, 6'-methoxy-, monohydrochloride, (8-alpha,9R)-
• Cinchonan-9-ol, 6'-methoxy-, monohydrochloride, (8-alpha,9R)- (9CI)
• 6'-methoxycinchonan-9-ol hydrochloride
• (R)-(6-methoxy-4-quinolyl)-[(2S,4S,5R)-5-vinylquinuclidin-2-yl]methanol hydrochloride
• (R)-(6-methoxyquinolin-4-yl)((2S,4S,5R)-5-vinylquinuclidin-2-yl)methanol hydrochloride
• (R)-(6-Methoxyquinolin-4-yl)((1S,2S,4S,5R)-5-vinylquinuclidin-2-yl)methanol hydrochloride
• (R)-[(2S,4S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol hydrochloride
• (R)-[(2S,4S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol;hydrochloride
• (8alpha,9R)-6'-Methoxycinchonan-9-ol monohydrochloride
• 6'-Methoxycinchonan-9-ol monohydrochloride, (8alpha,9R)-
• Cinchonan-9-ol, 6'-methoxy-, monohydrochloride, (8alpha,9R)-
• Cinchonan-9-ol, 6'-methoxy-, monohydrochloride, dihydrate, (8alpha,9R)-