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Most pharmacists know that acetylsalicylic acid (ASA) is derived from a natural source, and some will correctly name willow bark as the shrub that contains its predecessor, salicylic acid. There are hundreds of species of willow and the most common ones are Salix alba, Salix purpura, and Salix fragilis.1,2 They all belong to the Salicaceae family. The salicylate derivatives are found in greatest concentration in the bark of the scrub, but they are also present in the leaves.
Why do people use it?
People use willow bark for reasons that are often similar to the uses of ASA. It is used as an analgesic, for the symptomatic relief of mild colds, for headaches, inflammation pain, back pain, and arthritis.1,2
How does it work?
The compounds isolated from willow bark include naringenin glycosides, oligomeric procyanidins, flavonoids, and tannins.1,2 However, the most significant pharmacologically active ingredients are the salicylate derivatives salicortin, salicin, saligenin, and salicylic acid. Upon ingestion of willow bark, salicortin is hydrolysed to salicin, which in turn is hydrolysed to saligenin.1,3 The next step is the oxidation of saligenin to salicylic acid, which has know antipyretic, analgesic, and anti-inflammatory properties. A pharmacokinetic study estimated that 240 mg of salicin produced the same amount of salicylic acid as 87 mg of ASA.3
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