Willow Bark

Willow bark is the original source of aspirin. Traditionally willow bark has been used in the same way as aspirin, to reduce pain and fever. The Bayer company discovered a chemical process that improved the tolerance of synthetic salicylic acid (a related active component of willow bark), and modern-day aspirin was born. Our Willow bark extract is purified to contain 98% salicin, the naturally occurring active component.

Willow Bark in the treatment of low-back pain:
http://www.sciencedirect.com/science/article/pii/S0002934300004423