Foxgloves are a species of attractive flowering plants, the leaves of which were used to treat heart disease and other ailments in traditional folk medicine. This popular garden plant and medicinal herb is inedible, in fact its leaves, seeds and flowers are toxic.
Probably one of the best known examples of how a plant species, originally valued in traditional folk medicine, eventually led to the isolation of certain medicinally beneficial compounds, used to produce pharmaceuticals, are the species of flowering plants known as foxgloves. Prior to the mid-eighteenth century the pharmacological properties and uses of plants had not been studied in depth. Herbal formulas for the treatment of ailments were simply passed on by word of mouth.
In 1785 an English physician named William Withering (1741-1799) published a research paper that described an herbal mixture made by a lady from Shropshire, England, which she had used successfully as a treatment for dropsy (edema), due to heart failure. The medicinal mixture, past down from mother to daughter through the centuries, included leaves collected from (Digitalis purpurea) foxglove, prior to the plants flowers blossomed, which were then ground into a powder.
Withering wasn’t aware of the actual chemical compounds found in the plant and why foxglove leaves appeared to cure fluid retention due to heart disease but he knew that foxgloves, leaves, flowers and seeds, were poisonous if not taken in the recommended low doses. Moreover, that fact that the foxglove isn’t an herb to be toyed with was made apparent by the many macabre synonyms of the day such as witches gloves, dead men’s bells and bloody fingers.
Physicians often prescribed foxglove, in its herbal form, in too larger dose, which was known to cause nausea, visual disturbances, vomiting and fainting. A good reason not to self medicate with the herb. Also foxglove leaves are almost identical in appearance to the herb comfrey. Often the two herbs were confused in herbalists preparation, which caused many accidental poisonings. However, despite their toxicity foxglove species had been used for the treatment of numerous ailments such as nasal congestion, sore throat and as a compress for swelling and bruises since the 13th century.
The Digitalis or foxglove genus contains a number of cardioactive glycosides, the first of which, known as Digitalin, was identified in the mid-eighteen hundreds by the French scientists Theodore and Homolle Ouevenne. Then in 1875 Oswald Schmiedeberg (1838-1921) identified foxglove as a major source of the potent chemical named digitoxin. Another important chemical was isolated from (Digitalis lanata) woolly foxglove in 1930 by the English chemist Sydney Smith.
Eventually the various medicinal glycosides found in foxglove became a standardized mixture, used instead of the whole herb as a more accurate treatment. Today both Digitalis purpurea and D. lanata are cultivated for the pharmaceutical industry and marketed as the drugs Digitex,Lanoxin and Lanoxicaps. The drugs are considered crucial in the treatment of coronary heart disease, as they act directly upon the heart muscles; they slow the pulse and at the same time increase blood pressure and circulation.
Foxglove Varieties: Whether for medicinal intentions or not foxgloves became highly respected garden residents mainly because of their elegant towering flowers. This plant genus contains over 20 species which are native to Eurasia and North Africa, although they have been naturalized in North America since the eighteenth century. The genus name digitalis is from the Latin digitabulum, meaning thimble, a reference to the flower’s shape, and originally digitus, or finger.
Foxgloves or fairy gloves (some foxgloves are named in reference to fairies, e.g. fairy thimble, wee folk, folks glove, fairy’s glove) or Digitalis purpurea is a hardy biennial which grows up to 6ft tall and spreads to around 2ft. Some species grow to 8 feet tall which is not surprising considering they originated from woodlands. In its second season of life fairy gloves produce pretty purple or white tubular shaped flowers with purple spots to the throat. Popular cultivars of this species include ‘Excelsior’.
D. lanata or woolly foxglove, valued for its medicinal potency, is either a hardy perennial or biennial and considered an easier crop plant for pharmaceutical purposes than fairy gloves. Thought to have originated from the Balkans, Hungary and Turkey, woolly foxglove produces slightly smaller flowers with subtle shades of rose and white. Another hardy perennial is D. x mertonensis, commonly known as strawberry foxglove or Merton’s foxglove. This foxglove gets its name from its, slightly fuzzy, strawberry and pink blossoms set on graceful tall stalks. D. ferruginea, rusty foxglove or yellow rusty foxglove has brownish-yellow flowers speckled rusty brown.
Primary image, D. purpurea; Image credit.
The above image belongs to Pam Brophy and is licensed for reuse under creative commons Licence.