Salicin is extracted from Salix Alba. And salicin is an alcoholic β-glucoside. Salicin is an anti-inflammatory agent that is
produced in willow bark. 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, which is transformed to salicylic acid and has an action very similar to aspirin. Salicin is closely related in chemical make-up to aspirin. When consumed, the acetalic ether bridge is broken down. The two parts of the molecule, glucose and salicylic alcohol, then are metabolized separately. By oxidizing the alcohol function the aromatic part finally is metabolized to salicylic acid. Salicin elicits bitterness like quinine, when consumed. Alkaline cleavage of the glucoside populin produces benzoate and salicin.