New drugs are being developed all the time. Historically drugs have come from nature, as parts of plants and microorganisms have been extracted. One of the most famous discoveries was made by Sir Alexander Fleming, who discovered the antibiotic penicillin from the Penicillium mould. This antibiotic is still very important in the fight against disease.
Certain drugs can be extracted from natural sources, and have been known about for a long time. For example, willow bark was used by the ancient Greeks to help cure fevers and pains. It was later discovered that the active ingredient was salicylic acid. This was modified by chemists into the substance we call aspirin, which is less irritating to the stomach than salicylic acid. Another example is the heart drug, digitalis, which is extracted from foxgloves. As many plant species might still contain drugs that are yet to be discovered, it is important that plants are protected.
Once discovered, most plant drugs can be created in a laboratory by scientists at pharmaceutical companies. These companies now have synthetic versions of the plant extracts, and use these as the starting point to develop new drugs.