Drug Plants at the Market

... and very pretty ones at that: Foxgloves, or Digitalis purpurea.

I found these lovely specimens at a plant stall in the market square at Banbury. For those who do not know the place, Banbury is a pleasant small market town (obviously!) in the northern part of Oxfordshire. It is known throughout the world most widely for its association with the nursery rhyme ""Ride a cock horse to Banbury Cross" .

Today the sun shone during the afternoon, and this photograph of one of the pedestrian streets should give an idea of the place.

Foxgloves are famous, of course, for being the source of a variety of cardiac glycosides, and the term digitalis is used to identify the extracted drugs as well as the plant itself. The purified glycosides yield the well-known drugs digoxin and digitoxin.

Digitalis figured as Molecule of the Month for September 1996 , presented by the Chemistry Department at the University of Bristol. The web page describes the interesting story of how the medicinal properties of digitalis were discovered by the Scottish doctor William Withering.

This discovery probably marks the beginning of modern therapeutics.

Unfortunately, however, the drugs show steep dose-response curves, and minute increases in the dosage of these substances can make the difference between an ineffective dose and a fatal one. I have, if fact, suffered from digoxin poisoning myself, for reasons that do not concern us here, and the symptoms are pretty alarming! I've heard, too, that in gardens with many foxgloves on show, during the pollination season the pollen can settle on other plants in the garden, and there are reported cases of poisoning in humans by what should otherwise be harmless species. Take care! Wikipedia's comments about digitalis toxicity make entertaining reading (if you like that kind of thing, which I do), and I can vouch for the xanthopsia (visual colour disturbances) described towards the end:

The entire plant is toxic (including the roots and seeds), although the leaves of the upper stem are particularly potent, with just a nibble being enough to potentially cause death. Early symptoms of ingestion include nausea, vomiting, diarrhoea, abdominal pain, wild hallucinations, delirium, and severe headache. Depending on the severity of the toxicosis the victim may later suffer irregular and slow pulse, tremors, various cerebral disturbances, especially of a visual nature (unusual colour visions with objects appearing yellowish to green, and blue halos around lights), convulsions, and deadly disturbances of the heart.