Most Poisonous Plants

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Some species of rhododendron are poisonous to grazing animals because of a toxin called grayanotoxin in their pollen and nectar. People have been known to become ill from eating honey made by bees feeding on rhododendron and azalea flowers. Xenophon described the odd behavior of Greek soldiers after having consumed honey in a village surrounded by Rhododendron ponticum during the march of the Ten Thousand in 401 BC. Pompey’s soldiers reportedly suffered lethal casualties following the consumption of honey made from Rhododendron deliberately left behind by Pontic forces in 67 BC during the Third Mithridatic War. Later, it was recognized that honey resulting from these plants has a slightly hallucinogenic and laxative effect. The suspect rhododendrons are Rhododendron ponticum and Rhododendron luteum (formerly Azalea pontica), both found in northern Asia Minor. Eleven similar cases have been documented in Istanbul, Turkey during the 1980s.[28] Rhododendron is extremely toxic to horses, with some animals dying within a few hours of ingesting the plant, although most horses tend to avoid it if they have access to good forage. The effects of R. ponticum was mentioned in the 2009 film Sherlock Holmes as a proposed way to arrange a fake execution. It was also mentioned in the third episode of Season 2 of BBC’s Sherlock (TV series), and has been speculated to have been a part of Sherlock’s fake death scheme.



manchineelThe tree and its parts contain strong toxins, some unidentified. Its milky white sap contains phorbol and other skin irritants, producing strong allergic dermatitis. Standing beneath the tree during rain will cause blistering of the skin from mere contact with this liquid (even a small drop of rain with the milky substance in it will cause the skin to blister). Burning the tree may cause blindness if the smoke reaches the eyes.
The fruit is said to be possibly fatal if eaten, however, “fatalities from ingestion are not reported in the modern literature” (source 1991: Bygbjerg I.C. and H.K. Johansen: Manchineel poisoning complicated by streptococcal pharyngitis and impetigo. Ugeskr. Laeger 154 , 27-28 (1991).) and “ingestion may produce severe gastroenteritis with bleeding, shock, bacterial superinfection, and the potential for airway compromise due to edema. Patients with a history of ingestion and either oropharyngeal burns or gastrointestinal symptoms should be evaluated for admission in hospital. Care is supportive.” (source: Poisonous Plants: A Handbook for Doctors, Pharmacists, Toxicologists, Biologists and Veterinarians, by Dietrich Frohne and Hans Jürgen Pfänder. 2005).
In some parts of its range, many trees carry a warning sign (for example on Curaçao), while others are marked with a red “X” on the trunk to indicate danger. In the French Antilles the trees are often marked with a painted red band a few feet above the ground. On Bonaire, however, trees are unmarked.
The tree contains 12-deoxy-5-hydroxyphorbol-6gamma, 7alpha-oxide, hippomanins, mancinellin, and sapogenin, phloracetophenone-2,4-dimethylether is present in the leaves, while the fruits possess physostigmine.
The Caribs used the sap of this tree to poison their arrows and would tie captives to the trunk of the tree, ensuring a slow and painful death. A poultice of arrowroot (Maranta arundinacea) was used by the Arawaks and Taíno as an antidote against such arrow poisons. The Caribs were known to poison the water supply of their enemies with the leaves.[citation needed] Spanish explorer Juan Ponce de León was struck by an arrow that had been poisoned with Manchineel sap during battle with the Calusa in Florida, dying shortly thereafter.
To Europeans, the manchineel quickly became notorious. The heroine of Giacomo Meyerbeer’s 1865 opera L’Africaine commits suicide by lying under a manchineel tree and inhaling the plant’s vapours. In the 1956 film Wind Across The Everglades, a notorious poacher named Cottonmouth (played by Burl Ives) ties a victim to the trunk of a manchineel tree.





The cells of the Dieffenbachia plant contain needle-shaped calcium oxalate crystals called raphides. If a leaf is chewed, these crystals can cause a temporary burning sensation and erythema. In rare cases, edema of tissues exposed to the plant has been reported. Mastication and ingestion generally result in only mild symptoms. With both children and pets, contact with dieffenbachia (typically from chewing) can cause a host of unpleasant symptoms, including oral irritation, excessive drooling, and localized swelling. However, these effects are rarely life-threatening. In most cases, symptoms are mild, and can be successfully treated with analgesic agents, antihistamines, or medical charcoal. Gastric evacuation or lavage is “seldom” indicated. In patients with exposure to toxic plants, 70% are children younger than 5 years.




Abrus Precatorius:

Abrus-precatorius1The toxin abrin is a dimer consisting of two protein subunits, termed A and B. The B chain facilitates abrin’s entry into a cell by bonding to certain transport proteins on cell membranes, which then transport the toxin into the cell. Once inside the cell, the A chain prevents protein synthesis by inactivating the 26S subunit of the ribosome. One molecule of abrin will inactivate up to 1,500 ribosomes per second.
Symptoms are identical to those of ricin, except abrin is more toxic by almost two orders of magnitude; the fatal dose of abrin is approximately 75 times smaller than the fatal dose of ricin. Abrin can kill with a circulating amount of less than 3 micrograms.[citation needed]Abrin has an estimated human fatal dose of 0.1–1 µg/kg.[clarification needed] Ingesting the intact seeds typically results in no clinical findings, as they pass through the gastrointestinal tract due to their hard shell.
Abrus precatorius, called kudri mani in Tamil and guru ginja in Telugu, has been used in Siddha medicine for centuries. The Tamil Siddhars knew about the toxic effects in plants and suggested various methods which is called “suththi seythal” or purification. This is done by boiling the seeds in milk and then drying them. The protein is denatured when subjected to high temperatures which removes its toxicity.
In March 2012 a recall was issued for bracelets made using Jequirity Beans sold by the Eden Project and other outlets in the UK.
This plant is also poisonous to horses.
Symptoms of poisoning include nausea, vomiting, convulsions, liver failure, and death, usually after several days. Ingesting a single seed can kill an adult human. The seeds have been used as beads in jewelry, which is dangerous; inhaled dust is toxic and pinpricks can be fatal. The seeds are unfortunately attractive to children.


The Suicide Tree:

Cerbera_odollamCerbera odollam, commonly known as the Suicide tree, Pong-pong, and Othalanga, is a species of tree native to India and other parts of Southern Asia. It grows preferentially in coastal salt swamps and in marshy areas. It grows wild along the coast in many parts of Kerala, India and has been grown as a hedge between home compounds. It yields a potent poison, often used for suicide or murder.

The kernels of C. odollam contain cerberin, a potent alkaloid toxin related to digoxin, a poison found in foxglove. The poison blocks the calcium ion channels in heart muscle, causing disruption of the heart beat. This is most often fatal. Cerberin is difficult to detect in autopsies and its taste can be masked with strong spices. Therefore it is often used in homicide and suicide in India. In 2004, a team led by Yvan Gaillard of the Laboratory of Analytical Toxicology in La Voulte-sur-Rhône, France documented more than 500 cases of fatal Cerbera poisoning between 1989 and 1999 in the south-west Indian state of Kerala alone.
The seeds also have a long history as a poison in Madagascar. The poison was responsible for the death of 2% of the population (3000 people per year, 50,000 per generation) of the central province of Madagascar. The belief in the genuineness and accuracy of trial by ordeal using this poison was so strongly held among all, that innocent people suspected of an offense did not hesitate to subject themselves to it; some even showed eagerness to subject themselves to the test. On one occasion over 6000 people died in a single ordeal.[citation needed] The use of ritual poison in Madagascar was abolished in 1861 by King Radama II. However, it is believed that this practice may still occur in remote areas of the island.



Cicuta_maculata1-1Cicuta, commonly known as water hemlock, is a small genus of four species of highly poisonous plants in the family Apiaceae. They are perennial herbaceous plants which grow up to 2.5 meters (8.2 ft) tall, having distinctive small green or white flowers arranged in an umbrella shape (umbel). Plants in this genus may also be referred to as cowbane or poison parsnip. Cicuta is native to temperate regions of the Northern Hemisphere, mainly North America and Europe, typically growing in wet meadows, along streambanks and other wet and marshy areas. These plants bear a close resemblance to other members in the family Apiaceae and may be confused with a number of other edible and poisonous plants. The common name hemlock may also be confused with poison hemlock (Conium maculatum).

The Cicuta genus is one of many genera in the Apiaceae family which is in the order Apiales. The Apiaceae family is also known as Umbelliferae and both of these family names are permitted to be used by the International Code of Botanical Nomenclature. In Europe, Cicuta was not distinguished from the similar genus Conium before the year 1500. The first mention of the genus in the United States was in the eighteenth century. Carl Linnaeus formally described three species in 1753. The type species is C. virosa.Phylogenetic analysis using the sequences of nuclear ribosomal DNA internal transcribed spacer (ITS) loci was not conclusive but seems to show that C. bulbifera and C. virosa are monophyletic, while C. douglasii may not be. It was also suggested a specimen from California may warrant recognition as a distinct species. Other common names for the genus in general include poison parsnip, beaver poison, wild carrot, wild parsnip, and false parsley.



coniumConium is a genus of one or two species of highly poisonous perennial herbaceous flowering plants in the family Apiaceae, native to Europe and the Mediterranean region as Conium maculatum (known popularly as Hemlock), and to southern Africa as Conium chaerophylloides.

Conium contains the pyridine alkaloids coniine, N-methylconiine, conhydrine, pseudoconhydrine and gamma-coniceine (or g-coniceïne), which is the precursor of the other hemlock alkaloids.
The most noted of these chemicals is coniine, which has a chemical structure and pharmacological properties similar to nicotine. Coniine disrupts the workings of the central nervous system through action on nicotinic acetylcholine receptors. In high enough concentrations Coniine can be dangerous to humans and livestock.[6] Due to high potency, the ingestion of seemingly small doses can easily result in respiratory collapse and death.[8] Coniine causes death by blocking the neuromuscular junction in a manner similar to curare; this results in an ascending muscular paralysis with eventual paralysis of the respiratory muscles which results in death due to lack of oxygen to the heart and brain. Death can be prevented by artificial ventilation until the effects have worn off 48–72 hours later. For an adult the ingestion of more than 100 mg (0.1 grams) of coniine (approximately 6 to 8 fresh leaves, or a smaller dose of the seeds or root) may be fatal.


Castor Oil Plant:

castorThe castor oil plant, Ricinus communis, is a species of flowering plant in the spurge family, Euphorbiaceae. It belongs to a monotypic genus, Ricinus, and subtribe, Ricininae. The evolution of castor and its relation to other species are currently being studied using modern genetic tools.

The toxicity of raw castor beans is due to the presence of ricin. Although the lethal dose in adults is considered to be four to eight seeds, reports of actual poisoning are relatively rare. According to the 2007 edition of Guinness World Records, this plant is the most poisonous in the world. Despite this, suicides involving ingestion of castor beans are unheard of in countries like India where castor grows abundantly on the roadsides, which may be attributed to the rather painful and unpleasant symptoms of overdosing on ricin, which can include nausea, diarrhea, tachycardia, hypotension and seizures persisting for up to a week. However, the poison can be extracted from castor by concentrating it with a fairly complicated process similar to that used for extracting cyanide from almonds.
If ricin is ingested, symptoms may be delayed by up to 36 hours but commonly begin within 2–4 hours. These include a burning sensation in mouth and throat, abdominal pain, purging and bloody diarrhoea. Within several days there is severe dehydration, a drop in blood pressure and a decrease in urine. Unless treated, death can be expected to occur within 3–5 days, however in most cases a full recovery can be made.
Poisoning occurs when animals, including humans, ingest broken seeds or break the seed by chewing: intact seeds may pass through the digestive tract without releasing the toxin. Toxicity varies among animal species: four seeds will kill a rabbit, five a sheep, six an ox or horse, seven a pig, and eleven a dog. Ducks have shown far more resistance to the seeds: it takes an average of 80 to kill them. The toxin provides the castor oil plant with some degree of natural protection from insect pests such as aphids. Ricin has been investigated for its potential use as an insecticide. The castor oil plant is also the source for undecylenic acid, a natural fungicide.
Commercially available cold-pressed castor oil is not toxic to humans in normal doses, either internal or externally.



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