The medicinal use of willow bark is mentioned in Egyptian papyri, as well as the works of Hippocrates, Galen and Pliny the Elder. It was then largely ignored by western medicine, before being ‘rediscovered’ in 1736 by Reverend Stone, who sent the Royal Society a paper that described using it to treat ague (a fever). The active ingredient in willow bark was shown to be salicin in the 19th century. Rafaele Pina was able to convert this into a second compound, salicyclic acid. Unfortunately, salicyclic acid irritated the stomach, a problem solved by acetylation: the resulting acetylsalicyclic acid is today more commonly known as aspirin. Aspects of the history of this drug are outlined in the graphic above.
In 1971, John Robert Vane discovered the mechanism by which aspirin acts. Eleven years later, he, along with Sune Bergstrom and Bengt Samuelsson, was rewarded with the 1982 Nobel Prize for Physiology and Medicine. Aspirin reduces the rate at which prostaglandins (lipids that are involved in inflammation) are produced from arachidonic acid. It does this by permanently inactivating cyclooxygenase enzymes, by acetylating one of their serine residues (an -OH group is converted to -O(COCH3) )