Headache? Fever? Muscle pain? “Take two aspirin and call me in the morning.” This over-the-counter drug is one of the best remedies for reducing fevers and pain. Each year we collectively swallow 120 billion bitter doses to treat these conditions and to prevent heart attack, stroke and even colon cancer. That dosage is equivalent to 15 tablets a year for every human on the planet.
We owe the healing powers of aspirin to the white willow tree (genus Salix). In 1763 Reverend Edward Stone discovered a connection between the Peruvian (Cinchona officianalis) bark which had become the preferred antimalarial treatment in Europe, and the bark of a white willow. The so-called ‘fever tree’ is native to south America and is the principal source of the antimalarial drug quinine. This knowledge directly inspired Stone to experiment with the bark of the white willow, whose leaves and bark produced bitter tasting phenolics known as salicylates.
Stone said ‘a pound of bark taken from a common white willow was dried in a bag over a baker’s oven for more than three months, pulverized and then used to alleviate the distempers of 50 afflicted people’. The medicinal properties of bark from willow and other species were not new. Hippocrates (440-377 B.C.) prescribed the bark and leaves of the willow tree to reduce pain and fever. It also was mentioned by Dioscorides (c. 100 A.D.) and later by Pliny the Elder and Galen. However, it then fell into clinical disuse or had been relegated to the level of folk medicine. It took 90 years after Stone’s remarkable discovery until the chemical company, Bayer, began selling it in 1899 under the name Aspirin.
All plants make salicylates, but most don’t produce them at levels high enough to be protective. The high concentrates of salicylic acid in willows evolved to protect the tree from stressors like herbivores and pathogenic microbes, long before humans inhabited the earth. You and I and most other mammals have small amounts of salicylic acid regularly circulating in our blood. Why is that? Salicylates suppress the production of hormones called prostaglandins. Prostaglandins play a key role in turning on the inflammatory response in our bodies, causing inflammation and pain.
Headaches in humans and bitter leaves of willows share something important in common. Plants and humans use many of the same or similar chemicals, like salicylates, to regulate their bodies because these living organisms share a common evolutionary ancestor. This explains why so many chemicals produced by plants also have effects in us. So next time you see a willow, give thanks for the gift that makes our life a little more pleasant.
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