Long before pure chemicals were manufactured in labs, people used plants for medicine. There are many active ingredients derived from plants for use as drugs and medicines.
This is by no means a comprehensive list of all of the plants, names of chemicals, or uses for those chemicals, but it should serve as a useful starting point for further research.
For convenience, the common name of a plant is noted next to its scientific name.
Common names are imprecise and often assigned to completely different plants, so use the scientific name when looking for additional information concerning a plant.
List of Drugs From Plants
Reference: Much of the material contained in this table is from Leslie Taylor's Plant Based Drugs and Medicines from RainTree Nutrition (2000).