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Monday, June 15, 2015

An Early Cure for Malaria as Well as a Popular Ingredient with Gin

(image from NotFromUtrecht (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) via Wikimedia Commons

Would you believe that this popular beverage, the gin and tonic, contains an ingredient that was considered the cure for malaria during the American Civil War, World Wars I and II? Even in medical kits used during the Vietnam War, the chemical compound quinine was found among bandages and needles.
Medical tin of quinine sulfate used by surgeons during the Civil War.
(image from http://www.angelfire.com/oh3/civilwarantiques/1304webcat.html)


Here, a sargeant from Slate Hill, NY treats a malaria-strickened soldier with quinine during World War 2.
 (image from http://www.crazywebsite.com/Free-Galleries-01/USA_Patriotic/pg-WWII_Posters_Vintage/Vintage_WWII_Patriotic_Posters_United_States_America-_Malaria_1_jpg.htm)



During the Vietnam War, a chloroquine-resistant strain of malaria necessitated the use of quinine in conjunction with pyrimethamine to significantly reduce the rate of recrudescence (recurrence of symptoms after a period of quiet). Source: U.S. Army Medical Department, Office of Medical History 

Quinine is the active compound in the bark of the cinchona or "fever" tree discovered by South American Quechua Indians. When Jesuit missionaries started using it in the 17th century, it was called "Jesuits' Powder." In the 1930's, the Dutch controlled a monopoly on cinchona and provided about 20 million pounds of bark per year with quinine content as high as 13%.

 Cinchona
 (left image is Cinchona pubescens; right image is Cinchona trees from the Congo - from The Alcohol Professor)

 Because of the difficulty in growing cinchona in other places and dwindling supply, efforts were made to elucidate the structure and eventually synthesize the compound for pharmaceutical use. A German chemist named Paul Rabe provided initial evidence of quinine's structure:
 Quinine

The blue highlighted part of quinine is known as quinoline, an aromatic heterocycle that has synthetic applications for dyes, pesticides, and antibiotics.

The complete synthesis of quinine was achieved with stereochemical control by Gilbert Storck et al. from Columbia University in 2001. 


This gives you an  idea of the complexity involved in trying to synthesize a natural product. The key step involves changing a ketone functional group to an imine (respectively highlighted in red):


OTBDPS stands for tert-butyldiphenylsilyl ether 

 The other cool thing about quinine is that it fluoresces when you shine black light on it!

Tonic water contains no more than 83 ppm of quinine or 83 mg/L (image and data from wikipedia). To dilute the bitter taste of quinine, a lot of sugar is added to tonic water, and some add a twist of lime.

Resources
*"The First Stereoselective Total Synthesis of Quinine"; G. Storck, D. Niu, A. Fujimoto, E. R. Koft, J. M. Balkovec, J. R. Tata, and G. R. Dake; J. Am. Chem. Soc., 2001, 123, 3239-3242. doi: 10.1021/ja004325r
*From Pharmacy to the Pub-A Bark Conquers the World: Part3
*Jesuits' Powder
*Products of the Empire: Cinchona A Short History