What trees give medicine?

Too many to count... until the last century, all medicines came from plants and animals, including trees. For example, the bark of a willow tree is full of compounds similar to aspirin, so it was used to treat fevers. As chemistry and pharmacy became more effective, these compounds were first isolated, enabling purer or stronger forms then obtainable in nature. Towards the later half of the last century, chemists began to use their knowledge of how the medicines work in the body (pharmacology) to design medicines that are better than what is found in nature. For instance, lidocaine is a synthetic compound that is very similar in pharmacological structure to cocaine (which comes from a tree); however, it works as a pain killer without some of the negative side effects of cocaine.

My favorite plant-derived medicine is caffeine from the coffee tree!