As per my consideration, many (if not most) of the researchers of the field of Ethno-Medicine and Ethno-Pharmacology have many wrong concepts which they trust as right. It is just due to ignorance.
The main reason behind such ignorance is a partial study of the whole matter. It is like the different descriptions of the blinds who felt an elephant. Some say - it just a trunk, some leg, some tail, etc.
The study on the medicinal aspect of plant (Herbal) science is CONFINED within a single target - to identify components from the plant to synthesize chemically that component to market it as medicine to get huge profits.
For this, no study pattern even developed to evaluate the actual activity of any medicinal plant part. As an example: You eat the apple, but the usefulness/ activity of this fruit on your health is studied on diluent (methanol, ethanol, acetone, etc.) extract of dry apple, apple, fermented apple, etc., but NEVER ON SUCCULENT APPLE, that you eat.
There are many points, but I can only say that every Allopathic medicine (chemical drugs) is toxic above a certain dose. On the reverse, every toxic plant may have very important beneficial effects on our health in reduced or very reduced doses.