by Joelle Steele

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Since ancient times, many plants have been recognized for their poisonous properties, and people have used them to commit murder, causing immense suffering to their victims in the process. Plant poisons are fairly common; even seeds from the common apple (Malus sylvestris) have the potential to kill if ingested in large doses. Apple seeds contain a substance called amygdalin which, when chewed, swallowed, and then metabolized by the body, turns into hydrogen cyanide, a known killer for which there is no antidote. Fortunately, the human body can detoxify this cyanide if seeds are ingested only in very small amounts and, if they are ingested intact (not chewed), they usually pass through the digestive system without any ill effect.


Sometime between 3100 and 3000 BC, Menes, possibly the first pharaoh of upper and lower Egypt, studied poisonous plants and learned of the cyanide contained in the leaves and pits of the peach (Prunus spp.) and in the pits of cherries, apricots, bitter almonds and, as previously stated, in apples. The Egyptians knew of many other plant poisons as well, including opium (Papaver somniferum) and mandrake (Mandragora officinarum), the latter belonging to the Solanaceae or nightshade family.

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In 399 BC, the 70-year-old Greek philosopher Socrates was sentenced to death by suicide by drinking a concoction of water hemlock (Cicuta maculata, of the family Apiaceae, also known commonly as cowbane). The ancient Romans made use of plant poisons as well. Nero's official poisoner was Locusta, who helped wealthy women eliminate their husbands, usually using the leaves and berries of belladonna (Atropa belladonna), also known as "deadly nightshade," another member of the Solanaceae family. One of Locusta's alleged clients was Agrippina, the sister of Caligula, who hired Locusta to kill her third husband, Claudius, so that her son Nero could become emperor. Around 331 BC, to make sure the road was clear for Nero, Locusta likewise killed Claudius' son Brittanicus (Nero's half-brother), this time using cyanide.

Between about 132-83 BC, Mithradates VI Eupator, king of Pontus, an ancient area on the south coast of the Black Sea, sought protection from poisoning by taking small amounts of poisons to generate a resistance to them. It is from this practice that we get the word "mitridatize," meaning to render a person immune to a poison. According to Aulus Cornelius Celsus in De Medicina, Mithradates is said to have created a daily antidote of poisonous plants to protect himself from such poisons. Mithradates was also said to have tested many plant poisons on condemned criminals.


In the middle ages, the works of ancient scholars formed the basis for most knowledge of poisonous plants, including The Book of Venoms written by Magister Santes de Ardoynis in 1424. Such treatises were comprehensive but often confusing due to the use of so many different names for the same plants, a problem that still exists to this day, since many plants share the same common names.


As light dawned in the renaissance, plant poisons came into even more widespread use, particularly in the area of Naples, where poisoners favored aconite (Aconitum, also known as wolfbane and monkshood), belladonna, hemlock (Cicuta maculata), jimson weed (Datura stramonium), and strychnine (Strychos nux vomica). The notorious Borgia family used them for their own nefarious reasons, primarily to advance their political goals. Rodrigo and his son Cesare were adept at poisoning with a variety of deadly substances. Cesare's younger sister Lucrezia was close to her brother and was accused of many poisonings that were far more likely to have been committed by her brother. In 1589, Giovanni Battista Porta wrote Neopoliani Magioe Naturalis, a treatise on poisoning with plant substances, including aconite, almonds (cyanide), and yew seeds (Taxus baccata).


In 17th century England, there were several failed attempts to poison Queen Elizabeth, one with opium (Papaver somniferum). Elizabeth, whose mother Anne Boleyn had once tried to poison her father (Henry VIII), took action against possible poisonings by having her food tasted, her clothing checked for poisons, and by being mitridatized.


In early 19th century London, Thomas Wainewright used strychnine to remove several heirs, including his own uncle, so that he could inherit large sums of money. He was eventually caught and sent to a penal colony in Tasmania. By the latter part of the century, strychnine was relatively easy to obtain, and poisoning had become a fashionable crime of the rich, who now had their lives insured, making them easy targets for their less than loving heirs. Strychnine was a favorite, and Thomas Cream of England was executed in 1892 for using it to poison prostitutes.


In 1910 England, Dr. Harvey Crippen, a homeopath, was having an affair with Ethel Le Neve. His wife disappeared, and Ethel moved into his home, raising suspicions about the whereabouts of Mrs. Crippen. Scotland Yard intervened, and Crippen was ultimately found guilty and hanged for murdering his wife with hyoscine, the plant alkaloid found in henbane (Hyoscyamus niger) and various other plants of the Solanaceae or nightshade family.

The 20th century saw advances in technology that made the processing of poisons much easier. Any educated person could learn about plant poisons, obtain the plants (sometimes in their own back yards), manufacture the poisons, and commit murder. Cyanide, hyoscine, and strychnine were still popular and widely used, but designer poisons and more obscure plant poisons were appearing as well, forcing toxicologists to find new ways to detect these toxic substances. One such "new" poison was ricin, an extract of the castor bean (Ricinus communis) used for centuries in Africa.

Some plants that are normally used for medicinal purposes are toxic when administered in large doses, and another doctor in England, Dr. Shipman, was found guilty of murdering 15 patients with diamorphine, an opium derivative (Papaver somniferum) used to alleviate pain. However, as of 2005, it was believed he may have murdered as many as 265 patients.

It is interesting to note that the highly legally-obtainable tobacco (Nicotiana tabacum), which has been snorted, chewed, and smoked for centuries, is a member of the deadly Solanaceae family. It is probably one of the most deadly of plant poisons. In addition to the diseases it causes to the human body when used recreationally, it is also a poisonous plant in its own right. Smoking and chewing tobacco can result in optic neuropathy (vision deterioration and blindness), and ingesting parts of the plant can result in coma and death.

This article last updated: 10/09/2010.