ABSTRACT
Humans have used toxic compounds for millennia for medicinal purposes since, at subtoxic doses, some toxicants can be beneficial. By accurately regulating the dosage of plant toxicants ingested, a variety of maladies can be treated, including certain cancers as well as cardiovascular and infectious diseases. While many plant toxicants have a proven track record of being used in an unmodified form as medicines, they play another important role as lead compounds for synthetic modification for the design of entirely new drug substances. The chapter examines three major classes of plant toxicants, namely, alkaloids, isoprenoids, and phenols and quiñones, and highlights examples of plant drugs used clinically as medicines as well as some promising compounds under clinical evaluation. Alkaloids are well known and reasonably widespread plant toxicants, and it is considered that their primary ecological role is to serve as chemical defense substances to protect plants from predators.
