Synthetic medicines are often just a copied plant structure with a small change in the chemical structure so that it can then be patented. This is made, since you cannot patent already existing and made by nature. The problem with coping a plant structure, is that it is made based on the theory that there is only one active substance in a plant. But science is moving forward, and constantly advancing, and we today know that it is the complete chemical structure that is the active substance, not a single compound in the plant. As an example, at first it was thought that the active substance in Valerian was the essential oil, but in 1966 it was concluded that it was the Valepotriates, and finally in 1988 it was concluded that it was not known which of its substances was the active one, and concluded that the complete Valeriana plant works, not a few compounds of it. The "problem" for modern medicine, is that nature's chemistry is that it is seldom is a single active substance but many substances together that make it the active and more or less side-effect-free medicine.