The Foxglove (Digitalis purpurea) is as well known for its beauty as its toxicity. The humble poisin "Digoxin" a steroid-like (in structure) glycoside is both lethal and a lifeline for people with heart problems. The plant and extract (known as "digitalis") has been used as a poison for hundreds of years.
Digitalis is a potent "cardiac glycoside". In the body, the main component Digoxin (pictured above) is broken down (breaking of glycosidic bonds) into Digitoxin and sugars. The digitoxin stimulates the heart, increasing the heart rate dramtically. In conjunction with possible stomach upset and occasionally mental confusion, an overdose may lead to convulsions and heart attack. All parts of the plant, sap, seeds, leaves, flowers, nectar, contain digoxin, the leaves especially, even when dried. It is mostly animals, and small children attracted to the colourful tubular flowers that are affected by accidental ingestion. However, foxglove leaves may be confused with those of Comfrey which is traditionally steeped to make tea. Both have coarse, furry, similarly shaped leaves, and the young foxglove has only leaves no flowers or flowers stalks. Herbal remedies may occasionally be contaminated with Foxglove. In the past "tea" from the dried leaves has been used as a diuretic.
The potential of Digoxin for use in treatment for heart problems was realised many years ago, but little research was carried out until much later. Digoxin as previously mentioned is a glycoside and when the sugar (trisaccharide) group is digested the active part of the molecule (Digitoxin or Digitonin) is released (similar to saponin behaviour). This active part (extracted and pharmaceutically synthesised), now provides, with carefully prescribed doses, extremely effective treatment for particular heart conditions. It is marketed as Lanoxin (Digoxin minus two saccharide components). Both Lanoxin and Atropine are considered very important cardiac drugs in modern medicaine.