- The bitter-tasting bark of the white willow is a source of salicin (salicoside), salicortine, and tannin making it the herbal equivalent to aspirin. Pharmacological actions that have been confirmed in vitro include: arialgesic, alterative, febrifuge, astringent and antiperiodic. White willow exhibits favorable affects on the liver, the kidneys, and the heart . - Willow bark is the herbal analogue for aspirin and is an easy substitute with fewer side effects. Therefore, it can be good for the sy