Guest Post by Laura Cooper
Binomials can be a pain to learn, but they often have a hidden poetry. Deadly nightshade’s common name stresses its notoriety as a poison. But it’s binomial, Atropa belladonna, is far more beautiful and apt. The genus name is derived from Atropus, one of the three Fates of Greek Mythology, whose shears could cut the threads of life. The species name belladonna is the Italian for beautiful woman, named so because of the plant’s use in giving pleasingly dilated pupils. A figurative translation of the name could be femme fatale, appropriate for a plant whose main danger to humans is to the forager lured to pick and eat the glossy black berries.
The Herbarium has a large model of these berries displayed on a cabinet in the main room. It caught my eye as I was returning the gloves I wore to find Atropa belladonna Herbarium sheets. Compared to the shriveled fruits I had just seen, this was a regal fruit with the sepals like a ruff and a grandly arching stem. A belladonna indeed.
Atropa belladonna is one of the most common plants involved in poisoning throughout most of Europe and central Asia, but is still no minor threat. For example, the plant topped the list of plants causing severe poisoning in Switzerland between 1966-1994. Of a total of 24,950 cases of contact with poisonous plants, 135 cases (0.6% of total) were serious poisonings with sufficient information. Atropa belladonna was involved in 42 of these cases, but no deaths were reported. This doesn’t mean the plant should be treated lightly though. It has the potential to be quite dangerous.
As with many poisonous plants, it is very difficult to get an accurate measure of the lethal dose. Some report that an adult would be killed by 10-20 berries, whilst others report a case of children who had eaten eaten up to 40 berries and survived after hospitalisation.
A. belladonna‘s deadly potential is principally derived from three toxins, the tropane alkaloids hyoscine, hyoscyamine and atropine. The toxins have an anticholinergic effect, which means they affect neurones by competing with the neurotransmitter acetylcholine for muscarinic receptors. After a delay, this leads to an inhibition of the parasympathetic nervous system. This produces anticholingeric syndrome, whose symptoms are remembered by the mnemonic, “dry as a bone, blind as a bat, red as a beet, mad as a hatter, hot as a hare”. If the dose is high, this can lead to psychosis, convulsions, respiratory failure and death.
A. belladonna and its derivatives were favoured tool for the poisoner. In the late 19th century, the psychopathic American nurse Jane Toppan used atropine in concert with morphine to kill over 31 people. As atropine and morphine produce opposite responses, atropine “speeds up” the system whilst morphine slows down the body, Toppan balanced the doses of both drugs to prolong her victims’ struggle until a fatal dose was given.
However, atropine in the right hands can be a very useful chemical, even a lifesaver. It is the standard antidote for nerve gas poisoning, as it blocks the excess acetylcholine the nerve gas produced. It is also used to dilate eyes for examination by an ophthalmologist and is given to patients after cardiac arrest. Ironically, the very “poison” that Jane Toppan used to kill a victim whose death was originally recorded as heart disease is now used to help save patients from dying from a heart attack. There can always be a useful side to the proverbially deadliest of plants.