Poisoning from plants is a common fear but an extremely rare event. It is true that a few plant species in certain localities can produce serious toxicity like dander (Nerium oleander), foxglove (Digitalis purpurea), jequirity pea (Abrus precatorius), castor bean (Ricinus communis), water hemlock (Cicuta maculata), Jerusalem cherry (Solanaum pseudocapsicum), free tobacco (Nicotina glauca), jimsonweed (Datura stramonium), autumn crocus (Colchicum autumnale) and hepatotoxic mushrooms (Amantia phalloides and A. virosa).
In most cases, exceptional circumstances are required to produce severe poisoning. Even then, each year, a few deaths from plant poisoning do occur all over the world.
Example # 1. Yew (Taxus canadensis):
This is a very common ornamental hedge. All parts of Taxus except the red fruit contain poisons i.e. taxine A and taxine B within 1 hour of consumption it causes severe gastroenteritis which may be followed by convulsions, shock, coma and death.
It has also been classified as cardiotoxic. It has been recognized as an abortifacient by many women.
Example # 2. Castor Bean (Ricinus communis):
This plant contains ricin, a potent cellular protein toxin. Its seeds containing the toxin can be swallowed whole without injury, if, however, the seeds are crushed and the toxin is released, then severe gastroenteritis results. It may lead to CNS depression, cardiac dysrhythimias, coma and death.
Example # 3. Rosary Pea (Abrus precatorius):
It produces a toxin called abrin which is similar to ricin. It inhibits protein synthesis. All parts of the plant are toxic with seeds containing the higher amount of toxin.
Example # 4. Lily of the Valley (Convallaria majalis):
Convallarin and convallotoxin are found in this common garden plant. Convallotoxin and other glycosides act by inhibiting the enzyme Na+/K+ ATPase, Convallaria causes bradycardia and uncoordinated heartbeat.
Example # 5. Toxglove (Digitalis purpurea):
It produces a toxin called as “digitoxin” Digitoxin has been very valuable in medicine, but while it has saved many lives, it has also produced significant toxicity. It damages kidney. Many murders have been committed with digitalis as vehicle of death.
Example # 6. Oleander (Nerium oleander):
Its poisoning is based on cardiac glycoside. It predominantly causes GI and cardiac symptoms. Even meat roasted on the twigs of this plant becomes poisonous. Bees sometime use oleander pollen for their honey. The honey too, prepared in this manner has been found to be poisonous.
Example # 7. Monkshood (Aconitum napellus):
This plant is also known as wolfsbane. It is used by some as an herbal medicine under the name of aconite. It contains two alkaloid toxins i.e. aconine and aconitine. Upon ingestion, cardiac and neurologic symptoms have been reported. Several French recruits died from eating monkshood while on a training exercise during World War – I.
Example # 8. Black Hellebore (Helleborus niger):
This plant is also known as henbane. The entire plant is poisonous and contains hellebrin, helleborin, and saponins. It is a GI irritant, but its major effect is death from cardiac arrest.
Example # 9. Death Camas (Zygadenus venenosus):
They are called as grayanotoxins and include veratrine and zygadenine. They cause bradycardia and hypotension as well as cholinergic symptoms namely salivation, lacrimation, rhinorrhea and emesis. They have been mistaken by campers for onion.
Example # 10. Azalea (Rhododendron):
These plants are omnipresent. They share many properties. They produce a specific poison called andromedotoxin. This toxin causes GI stress, respiratory difficulty and bradycardia. Some birds eat these bushes which renders their flash poisonous.
Example # 11. Mushrooms:
Five thousand mushroom species are known to occur in United States alone. Approximately 2% of these species are toxic. Poisonous mushrooms contain toxins that are as diverse as mushrooms, themselves.
The mushroom portion of the fungus is the reproductive structure that grows from underground mycelium as a densely packed cap and stipe of interwoven hyphal strands. This structure contains the spores that germinate and form new mycelia. Variation in size, shape, color, spore and other microscopic structures aids in the identification of mushroom species.
There are about eight groups of compounds secreted by different species of mushrooms:
i. Cyclopeptide group – Amantia phalloides., A verna, A. virosa, A. bisoporegera and Galerina sp.
ii. Monomethyl hydrazine group – Amantia muscaria and A. patherina
iii. Coprine group – Gyromitra sp.
iv. Muscarine group – Clitocybe and Inocybe sp.
v. Ibotenic acid and muscimol group – Coprimus sp.
vi. Hallucinogen group – Psilocybe, Panaeolus, Gymnopilus
vii. Gastrointestinal group – Chlorophyllum molybditis
viii. Renal failure group – Cortinarius sp.
The cyclopeptide amatoxins of Amantia and Galerina can cause severe hepatorenal dysfunction. A phalloides is the prominent European poisonous mushroom. Group II mushrooms cause gastritis, less often hemolysis, hepatorenal dysfunction, convulsions and death follows ingestion. Coprine mushrooms of group III cause hyperacefaldehydemia. Muscarine mushrooms are reported to secrete muscarine.
TI causes cholinergic excess syndrome within 30 minutes. Ibotenic acid species (A. muscaria) that contain psychoactive isoxazole derivatives, produce hallucinations. They cause muscle spasm, confusion, intoxication drowsiness and sleep.
The main toxin of hallucinogenic mushrooms is psilocybin. This has lysergic acid diethylamide like properties and produce alterations in autonomic function, motor reflexes, behavior and perception gastrointestinal weakness, nausea, vomiting and diarrhea.
Example # 12. Atropa Belladonna (Deadly nightshade):
All parts of Atropa are dangerous including roots, leaves and berries. Berries contain the highest content of toxic alkaloids. These are known as atropine, hyoscine and hyoseyamine and refers to the practice during Renaissance of placing an extract of Atropa inorder to achieve dilated pupils, regarded by many as the attractive feature.
Example # 13. Datura Stramonium (Jimsonweed):
Jimsonweed is also called as thornapple, stink weed and Devil’s trumpet. It contains all the three alkaloids as described above. Severe cases may lead to loss of sight, convulsions, coma and death. Many soldiers died after eating this plant when famine broke out in 1666 in the early American colony, Jamestown in Virginia.
Example # 14.Mandragora Officinarum (Mandrake):
This plant, in addition to atropine and hyoseyamine, contains momdragorin which is considered to promote fertility and had aphrodisiac properties. It was also associated with witchcraft and women, who possessed mandrake were executed in 17th century in Germany.
Example # 15. Neurotoxic Plants:
i. Hemlock (Conium maculatum):
The toxins found in this plant are piperidine alkaloids, coniine and gamma coniceine. Their primary lethal consequences are respiratory failure. They also produce nicotinic effects viz. salivation, mydriasis, tachycardia followed by bradycardia. Pluto, the great Greek philosopher has described the death of Socrates due to hemlock.
ii. Water Hemlock (Cicuta virosa):
Water hemlock is a weed commonly found along lakes and streams. Its toxin is known as cicutoxin that specifically works upon brain and spinal cord. It causes rapid onset of status epilepticus.
iii. Curare (Chondrodendron tomentosum):
The red Indians in Amazon and South America dip their arrows with this poison which paralyzes the skeletal muscles of their prey. Death results from respiratory failure.
Example # 16. Cyanogenic Plants:
All those plants that are able to form cyanide under certain conditions are called as cyanogenic plants. Most cyanogenic substances are glycosides-meaning thereby that a carbohydrate moiety is part of their structure. Fortunately the cyanogens are not found in fruits but present in leaves, stem and bark. Examples are apple, apricot, cherry, peach, and black berry.
i. Hydrangea Paniculata:
Hydrangea contains two cyanogenic glycosides known as hydrangin and amygdalin. Symptoms of poisoning are nausea and gastroenteritis.
ii. Apricot:
This fruit contains amygdalin. Interestingly amygdalin has become celebrated as an alleged cancer cure and is most commonly called as laetrile. Laetrile is more likely to cause harm rather than benefit.
iii. Cassava (Manihot esculenta):
This is a common dietary component in many parts of the world. It contains a cyanogenic glycoside known as linamarin. Tropical ataxic neuropathy has been observed in Nigeria and epidemic spastic paraperesis has been observed in certain parts of equatorial Africa.
Example # 17. Hepatotoxic Plants:
Akee when unripe, contains hypoglycin, a compound believed to be teratogenic and a cause of toxic hypoglycemic syndrome (also called Jamaican vomiting sickness). Akee is a staple food of Jamaica and British West Indies. Raw or spoiled fruit is to be avoided.
Example # 18. Solanaceous Plants:
About 1700 species of these plants are known till date. They all contain salanaceous alkaloids. Many solanaceous alkaloids contain the same basic aglycone but differ in the number and type of carbohydrate molecules. Solanine occurs in the common potato. Solanum tuberosum. Levels of solanine above 20 ppm are dangerous. Solanine is a cholinesterase inhibitor. It causes cholinergic symptoms such as salivation, trembling, progressive weakness and paralysis.