TONIC WATER WON’T HELP WITH COVID-19
There seems to be some confusion between quinine and drugs hyped as treatments
I have never been fond of drinking bitter tonic water, but there is a sweet use to which it can be put. The quinine in the water, which is responsible for the distinct bitter flavour, can make for a great demonstration of “fluorescence.” This is a phenomenon by which radiation of one wavelength is absorbed by a substance and is immediately reradiated at a different wavelength. The effect lasts as long as it remains exposed to the incident radiation, in contrast to “phosphorescence,” in which the emission continues even after the exciting radiation has been removed.
In the case of quinine, electrons in the molecule can absorb “black light,” which is ultraviolet light in the 320 to 400 nanometre range, and transition to an excited state. Energized electrons then return to the relaxed state, and when they do, they emit some, but not all of the energy they had absorbed. This lower energy, higher wavelength, radiation is in the form of visible blue light. Shine black light on a glass of tonic water and it will emit a beautiful blue glow! But you can forget about tonic water shining light on a COVID -19 infection.
Why are people asking about a connection between tonic water and COVID-19 in the first place? It seems to be prompted by confusion about quinine and chloroquine, the drug being hyped for the treatment of coronavirus infection. Both quinine and chloroquine are antimalarial drugs, so maybe if chloroquine works, which has not been scientifically demonstrated, then quinine may work, as well, the thinking goes.
While quinine and chloroquine have some similarity in molecular structure, they are significantly different. That difference may not matter when dealing with the malaria parasite, but dealing with a virus is a different story. Furthermore, even if quinine had some antiviral activity, the amount added to tonic water, about 80 milligrams per litre, is far too little to have an effect.
While tonic water as produced today has no medicinal effect, there was once a version that did. Let’s go back to colonial India in the 19th century, when British soldiers were required to take quinine to prevent malaria. They were told to stir the powder in water and drink the “tonic,” a term that derives from the Greek “to stretch,” since the tonic was meant to stretch health. Many soldiers found the taste of quinine too bitter and did not take the medicine.
How to persuade the soldiers to take the life-saving drug? Mask the bitter taste. But with what? Juniper berries did the job nicely and these are the berries that give gin its distinctive flavour. Soldiers didn’t need much convincing to mix their “tonic” with gin and they happily downed the gin and tonic. And a classic beverage was born.
Where did the idea that quinine could prevent malaria come from? For that, we take a historical trip to South America. When Jesuit missionaries arrived in the latter part of the 17th century to teach the Indigenous people there about Christianity, they also learned something themselves. The Incas had a way of treating fever, a characteristic symptom of malaria, by drinking a brew they made from the bark of a tree. That tree was the cinchona tree, the bark of which harbours quinine, which of course was not known at the time. In any case, the Jesuits introduced the powdered bark to Europe, where it became known as “Jesuit powder “or the “Pope’s powder.”
In 1820, French researchers Pierre Joseph Pelletier and Joseph Bienaimé Caventou managed to isolate the bark’s active ingredient and coined the term “quinine” from the Inca “quina-quina,” meaning “bark of bark.” Prior to 1820, the bark was first dried, ground to a fine powder, and then mixed into a liquid, usually wine, which was then consumed. Once quinine could be extracted from the bark, it became easier to determine dosages and large-scale use of quinine as a prevention for malaria began around 1850.
There was never enough quinine to meet the needs and that raised the prospect of a synthetic version. Since molecular structures could not be determined at the time, the difficulty of this task was not realized. Nevertheless, a futile effort to make quinine from coal tar in 1856 by young William Henry Perkin had a serendipitous outcome. Instead of quinine, he accidentally produced a synthetic dye, mauve, that laid the foundation not only for the commercial dye industry, but for the pharmaceutical industry, as well.
The synthesis of quinine was finally achieved by Nobel Laureate Harvard chemist Robert Woodward in 1944, but it was far too complicated for commercial use. To this day, the cinchona tree remains the only source of quinine. A further problem was that with the increased use of quinine, the malaria-causing parasite was developing resistance to the drug. This stimulated a search for molecules that had some similarity in molecular structure to quinine but could be more readily synthesized.
One of these, developed by the Bayer Company in Germany in the 1930s was chloroquine. Since chloroquine had significant side effects, a derivative with a better side effect profile, hydroxychloroquine, was introduced by the Sterling pharmaceutical company in 1955. These drugs are the ones now being tried for COVID -19 infections. It remains to be seen if the outcome will be bitter or sweet.
Joe Schwarcz is director of Mcgill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m. joe.schwarcz@mcgill.ca