For centuries it has been recognized that plants relate to human health and well-being in many ways beyond their fundamental role as primary sources of food and energy. Many of the unique plant constituents have pronounced effects on animal systems or in the human body; some of them are potentially harmful and represent a risk in the use of a parttcular plant or in the exposure to it, others are useful as medicinal agents in the treatment of diseases. Many of the latter are extracted from plant materials on a large scale for marketing as drugs and even more of them have served as structural...