PRINCIPLES OF TOXICOLOGY

420 PROPERTIES AND EFFECTS OF NATURAL TOXINS AND VENOMS
Figure 17.4 The common foxglove, Digitalis purpurea. The leaves of this beautiful flowering perennial contain
several cardiac glycosides that are used in the medical treatment of congestive heart failure. Unfortunately, foxglove
leaves are easily confused with the leaves of the common comfrey, whose leaves are commonly used to prepare
herbal teas, and there have been several medical reports of foxglove poisoning due to this error in plant identification.
tered orally at recommeded doses, usually as a tea or a tablet. However, individuals who chronically
consume excessive amounts of ginseng may experience deleterious side effects including insomnia,
skin eruptions, diarrhea, and hypertension.
Fortunately for us, most saponins are not readily absorbed from the gastrointestinal tract as
glycosides. Instead, intestinal glycosidase enzymes cleave away the sugar groups attached to the
3-B–OH group on the sterol skeleton, and this practically abolishes their toxicity. The non-polar
aglycones are readily absorbed and probably are pharmacologically active components. The
saponins are a large, chemically diverse group. Despite a vast effort by chemists to decipher their
complex structures, very little is yet known about their pharmacological mechanisms of action.
They probably exert a variety of actions through multiple cell receptors. In spite of their popularity