By Greg Kincheloe

Nearly everyone that enjoys cocktails has a go-to default drink. These drinks vary widely according to everyone’s personal taste, but often share two qualities: 1) they are widely known, implying that any self-respecting bartender should know how to make them, and 2) they are almost impossible to mess up, making them a safe bet for a fun night out. Based off of a brief peer survey, common default drinks are a whiskey sour,  an old-fashioned, and a negroni but my default is a gin and tonic (Figure 1). Though its bitterness may make it seem like an odd choice when the long list of classic cocktails includes many sweeter and smoother drinks, the history-buff inside me can’t resist an interesting origin story, and for me, that story makes all the difference.

If you ever taste straight tonic water, you will find that it is surprisingly bitter for such a popular cocktail mixer. In addition, if you ever drink a gin and tonic in a bar with a blacklight, you may be surprised to see that your drink glows in the dark. As it turns out, both of these characteristics – the bitterness and blue fluorescence – are both results of a chemical in tonic water called quinine. Quinine, an alkaloid compound that is extremely bitter to the taste, also happens to cause rapid schizonticidal (death at a particular phase of some protozoa infections) effects when in high enough concentrations in the bloodstream¹. Though it is known to inhibit nucleic acid synthesis, protein synthesis, and glycolysis, the exact mechanism of action still remains elusive. Despite the remaining questions surrounding this mechanism, this unique anti-protozoan activity of quinine is the historical foundation for the creation of a truly classic cocktail. 

While the exact timing and characters involved in the discovery of quinine is up for debate, it undoubtedly starts from its source, the cinchona tree native to South America. Sometime during the 17th century, it was discovered that the bark of this tree, though bitter and nearly unpalatable, could be used to treat fevers (for more information on another wonderful medicine that comes from tree bark, see Hannah Johnson’s LTS article on Aspirin), a quality which rapidly made the bark a prized and highly sought-after remedy in Europe^1,2. Later, in the 18^th century, a Scottish doctor named George Cleghorn found that the quinine in the cinchona bark could be used to treat malaria².  At high enough concentrations in the bloodstream, quinine effectively killed off many forms of Plasmodium, the genus of protozoa that causes malaria¹. By the mid-1800’s, quinine was being purified en masse and used for treatment for malaria. Half a century later, when the British empire forcibly colonized India and imposed its own rule there, British soldiers were issued water with high amounts of quinine as a prophylactic against malaria^2,3. This water, which later became marketed as tonic water, was incredibly bitter, so soldiers began cutting it with large amounts of sugar, citrus, and – you guessed it – gin. And thus, the famous cocktail was born.

Such was the fame and usefulness of the gin and tonic, that Winston Churchill was once quoted as saying, “The gin and tonic has saved more Englishmen’s lives, and minds, than all the doctors in the Empire.”³ Today, tonic water as a cocktail mixer contains much less quinine than it did historically, to the point where one would have to drink 67 liters of it to get an effective dose to treat malaria. It should also be noted that quinine is no longer the primary treatment for malaria, as there are more effective treatments with fewer side-effects now available, such as chloroquine (a synthetic analog of quinine) as well as recent vaccine developments that protect against the most dangerous species of Plasmodium^1,5. Rising levels of resistance against anti-malarial drugs have spawned many other treatments with different mechanisms of action. However, quinine and its synthetic analogs are still known as a viable second-line treatment for malaria and is still used often across the globe⁴. So the next time you go to a bar and panic-order a drink when the bartender asks what you want, make it a gin and tonic, just so you can share a good story.

TL:DR

• Quinine is the reason your tonic water tastes bitter and fluoresces.

• Quinine was and still is used to treat malaria across the globe. 

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References

1. Achan J, Talisuna AO, Erhart A, Yeka A, Tibenderana JK, Baliraine FN, Rosenthal PJ, D’Alessandro U. Quinine, an old anti-malarial drug in a modern world: role in the treatment of malaria. Malar J. 2011 May 24;10:144. doi: 10.1186/1475-2875-10-144. PMID: 21609473; PMCID: PMC3121651.
2. McGill University (2018, September 27). Did you know that malaria spawned the gin and tonic? McGill Office for Science and Society. https://www.mcgill.ca/oss/article/did-you-know/malaria-reason-behind-gin-and-tonic
3. Raustiala, K. (2013, August 28). The Imperial Cocktail: How the gin and tonic became the British Empire’s secret weapon. Slate. https://slate.com/technology/2013/08/gin-and-tonic-kept-the-british-empire-healthy-the-drinks-quinine-powder-was-vital-for-stopping-the-spread-of-malaria.html
4. Center for Disease Control (n.d.). Treatment of Malaria: Guidelines for Clinicians (United States). CDC.https://www.cdc.gov/malaria/diagnosis_treatment/clinicians1.html#:~:text=The%20preferred%20antimalarial%20for%20interim,not%20adequate%20for%20interim%20treatment.. 
5. WHO recommends groundbreaking malaria vaccine for children at risk. 2021, October 6. World Health Organization. https://www.who.int/news/item/06-10-2021-who-recommends-groundbreaking-malaria-vaccine-for-children-at-risk