Poisonous medicinal plants

Opium is a source of many narcotic substances. Morphine, a pain killer and cough relieving substance, is also derived from the opium poppy.

Deadly nightshade is closely related to henbane and very toxic. Atropine from deadly nightshade is used in eye surgeries to get the eye musculature to relax.

Foxgloves contains digitalis, one of the important substances in heart medicines.

It is lethally dangerous to use the actual plants themselves as medicines. In the medicines prescribed by doctors is it known exactly how much active substance is in each dose. That is not the case with the plants in nature.

Foxglove helps against heart failure

The leaves of the floxglove
contain very potent heart drugs
and should therefore not be
Photo: Håkan Tunón.

Heart medicines are still being extracted from the foxglove, i.e., the species of the genus Digitalis. The foxglove played no significant part within the school medicine during the 17th and 18th centuries. This however changed in 1775 when the English doctor, William Withering, described having observed how a traditional healer from Shropshire successfully treated a case of dropsy with a decoct of foxglove. Dropsy is a form of oedema (swelling) that can be caused by inadequate heart function. This observation triggered Withering to experiment with foxglove on patients with dropsy. In 1785 he published his results in the book ”An Account of the Foxglove, and some of its medical uses: with practical remarks on dropsy.” Ever since then Digitalisleaves have had worldwide success.

The first time a mixture of so called cardio-active glycosides was extracted from the leaves of the foxglove was in the middle of the 19th century. Since then chemical methods have improved and we can now differentiate between the various Digitalis-glycosides and today we are aware of many different ones.

Several of these are registered drugs in Sweden. Very similar substances are also found in the lily of the valley (Convallaria majalis) and in the common toad (Bufo bufo). The lily of the valley is very toxic and the poison consists of various cardio-active substances. Its leaves used to be sold at pharmacies as heart medicine.

Deadly nightshade relieves cramp

Deadly nightshade – the whole plant
contains muscle relaxing substances. It is
therefore highly poisonous.
Photo: Håkan Tunón.

The plant belladonna or deadly nightshade, Atropa belladonna, got its name from an old Italian custom of dropping the juice of the bush’s berries into the eyes. This was mainly used as a beauty product. When the juice came into contact with the eye, it relaxed the circular muscle which controls the size of the pupil and the pupil could not contract.

The women who used it therefore got big dark eyes which were considered beautiful, thus giving rise to the Italian name belladonna.

Atropin is a very powerful poison that has been refined from the plant. It is a muscle relaxant and is used for antispasmodic drugs e.g. during operations. It affects the muscles by inhibiting a certain part of the nervous system. That is why, apart from cramp relief, it has side effects that relax the circular muscle of the eye, reduce the production of saliva and make urination difficult. Atropin is used in the army as an antidote to nerve gas. This is because some nerve gases affect the nerves in exactly the opposite way and so one kind of poison cancels out the other.

Opium – a latex from Hell?

Opium poppies used to be grown
in the Linnaeus’ Garden, Uppsala.
Photo: Jan G. Bruhn.

The medicinal effects of the opium poppy have been known for several thousand years. The milky juice was seen to be sleep-inducing which inspired Linnaeus, when he named the plant Papaver somniferum. Somniferum means soporific. The word opium comes from the Greek opos which meanslatex and the name morphine comes from Morpheus, the Greek god of sleep.

Opium was being used in Europe as early as medieval times. When Europeans colonised Asia, the Portuguese took over the trade in opium between India and China.

People in China started smoking opium for pleasure as well as for its medicinal qualities. Smoking opium involves inhaling a dry opium distillate. The opium smoker falls into a torpor and experiences pleasant dreams. A moderate opium smoker will spend a large part of the day being intoxicated and afterwards he will exhibit very little interest in his surroundings. Long term use of opium is said to lead to a dulling of the intellect.

It has long been known that opium is dangerous and should be used accordingly. The dose is therefore extremely important. Pharmacies used to sell Opium Tincture, opium dissolved in alcohol for internal use against panic attacks or diarrhoea. This is because opium, apart from its soporific properties, also slows down peristalsis – the movements of the colon. The colon is anaesthetised, so reducing the diarrhoea.

When you score an unripe opium
poppy capsule, a white milky latex
runs out. This blackens as it dries.
It is what we call opium.
Photo: Ulf Nyman.

Chemistry had progressed so far at the beginning of the 19th century that chemists could extract and refine medically active substances from opium. The first time the principal component, which was named morphine, was isolated, was in 1803. Then in 1818 another substance was found that was given the name narcotine. Here too opium’s narcotic – sleep inducing properties – have had a role to play. The name was later changed to noscapine.

The substance codein was first refined in 1832 and the name is inspired from the Greek word for poppy head, kodeia. In 1848 papaverin was isolated. Its name is derived from Papaver which is Latin for poppy. The active substances in the latex of the opium poppy are of a type which is known as alkaloids.

Many opium alkaloids are still used in modern health care for symptoms that were formerly treated with opium. The most well-known of these is morphine which is an analgesic. It is addictive and is therefore used restrictively. Instead codein is used more and more frequently. Codein also has analgesic properties but it is not so addictive. Papaverin is used in modern medicine as an antispasmodic for the relief of cramp. This effect of opium was described early in a Swedish book of herbs from the 17th century where it states that, “Opium in relatively large amounts relieves cramp (if the amount is too large, it is lethal).” In the same book you can read, “Opium relieves Coughing” and nowadays noscapine is used in certain cough medicines. Codein, too, gives cough relief.

Morphine has also been modified as ethylmorphine, which is found in certain cough medicines. But the most famous, or rather notorious, semi-synthetic morphine derivative is heroin, a very potent cough relief, but which is rightly no longer considered suitable for use within medical care.

The Opium Wars

The smoking of opium became a threat to the economy of the Chinese Empire and so the Chinese Emperor prohibited all trade in opium in 1729. During the same period the British occupied northern India with its poppy fields. Despite the prohibition the English East India Company exported large quantities of opium to China and by 1835 the export had reached nearly 2 000 tons of opium a annually.

A painting of the attack on China by the English fleet at Dinghai in 1840.

The Chinese authorities were not pleased with the situation and chose to solve the problem with force. The Chinese captured and destroyed over 250 tons of opium. The English, in their turn, were not pleased and this led to the First Opium War in 1839. Since England was victorious, the yearly export of opium to China increased and by 1850 more than 3 000 tons were being exported annually. The displeasure of the Chinese led to another Opium War (1856–1858) and, this time too, it resulted in an English victory. The opium trade continued and England forced China to legalise the trading of opium. This went on up to 1906 when the English merchants were forced to stop their opium business in China as a result of pressure from the USA.

Last modified: 2021-11-29