White Willow Bark Extract Contains salicin, which is a chemical similar to aspirin (acetylsalicylic acid). In combination with the herb's powerful anti-inflammatory plant compounds (called flavonoids), salicin is thought to be responsible for the pain-relieving and anti-inflammatory effects of the herb. White willow works slower but lasts longer than aspirin and has less side gastronomic side effects due to the large amounts of tannin that protect the stomach.
Salicin is an alcoholic β-glucoside. Salicin is produced in (and named after) willow (Salix) bark and acts as an anti inflammatory agent in the human body.[2] Salicin is also commonly found in the bark of Populus species, and the leaves of willows and poplars. It is also found in castoreum, which was used as an analgesic, anti-inflammatory, and antipyretic. The activity of castoreum has been credited to the accumulation of salicin from willow trees in the beaver's diet.