Very many books have been written on the relationships of plants to medicine, so here only a few brief comments can be made. The Babylonians imported myrrh for medicinal uses by 3000 B.C., and trade between Babylon and Egypt was documented on a tablet by 2250 B.C. Mention of medicinal plants occurred in the earliest Chinese monograph (2700 B.C.) and in India (1500 B.C. in Rig Veda). Famous ancient physicians who used plant medicines were Hippocrates and Theophrastus (Greeks), Galen and Dioscorides (Roman), and Avicenna (Arabic), and all five had plant genera named in their honor. Materia medica of Dioscorides was the classic textbook of plant medicines for nearly 1500 years, and the work by Pliny the Elder also contained valuable botanical medicine. Early botanists, including Linnaeus, were physicians (MDs), lasting as late as the 19th century, when botany became an academic discipline in its own right at famous universities and botanical gardens.
Folk medicine is known from every continent, essentially every tribe. The person in charge of medicines was very powerful and influential, and often medicine and religion were highly integrated as shamanism. Uses of plants by a shaman date back at least 10,000 years for hallucinogens, and general uses of plants as medicines must be even more ancient among hunter-gatherer societies. Within each region people must have practiced trial and error experimentation with plants as medicine until beneficial results were obtained, and then the cure was transferred by word of mouth and hand-me-down lore, what is termed folk medicine. There are professional journals today that specialize in publishing research results on ethnopharmacology, i.e., plants used in folk medicine.
The first antiseptics were plants, in particular spices mixed with resins and natron (sodium sesquicarbonate), as in ancient Egypt, where this combination prevented putrefication. The first very effective antipyretics (lower body temperature during fever) were plants such as willow (Salix) and quinine (Cinchona). In the 1880s the plant alkaloids cocaine and then atropine were the earliest local anesthetics for delicate eye surgery. As late as the 1970s, 25% of drugs in use in North America and Europe had some plant extract or plant derivative. Now that number has decreased by the origins of so many synthetics, but plants are still extremely valuable sources for some of our most powerful anticancer substances and relaxants. Poisons from plants made legends of Borgia, Medici families in the Middle Ages, famous cases in ancient Greek and Roman times, and still occur in real life today in our mystery novels and films. Many of the psychoactive drugs of today’s culture, originally medicines, come from plants, and now constitute an enormous financial drain and criminal nightmare for the world.
The terms medicines, drugs, and poisons can all apply to a single plant chemical, which at one concentration is curative, at another a potentially addictive substance, and at a higher concentration a harmful or lethal poison. Some of the strongest plant medicines must be administered very carefully at extremely low dosages to avoid toxic effects, and dosage must be adjusted for body weight, because children and smaller women will experience toxicity with smaller amounts than heavier males. Therefore, use of plant medicine has always required the dispenser to understand limits of its use--the art of healing.