Poisonous Plants, Fungi, and Algae

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Poisonous Plants, Fungi, and Algae

• IV - Poisonous Plants

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Poisonous Plants

• Early societies knew the dangers of poisonous
  plants and avoided eating them
• Knowledge of these plants passed on
• Poisonous plants also put to use
• Used by many societies to capture prey
• Possibly even to poison enemies
• Many South American tribes still use blowguns
  with poisonous darts

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Active Compounds

• As with medicinal and psychoactive plants, the
  active compounds include terpenes, phenolics,
  alkaloids, and glycosides
• Some plants have medicinal or psychoactive
  properties
• Several well known poisonous plants that have
  some historical and or medical importance
• digitalis
• strychnine
• poison hemlock

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Poisonous Plants Today

• In contemporary society the biggest danger is
  accidental poisonings by common house plants and
  yard plants
• About 5 of all poisoning cases are caused by
  yard plants (not including mushrooms)
• Young children are most likely to be poisoned by
  these plants

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A few Poisonous Plants
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Dumb cane
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Dumb cane

• The stem and leaves contain calcium oxalate
  crystals which can cause intense burning and
  irritating sensation to the mouth and tongue
• Oral toxicity is well known with severe swelling
  of the lips, mouth and tongue which can lead to
  difficulty of swallowing and breathing.
• Death can occur if base of the tongue swells
  enough to block the air passage
• Also a problem with pets especially cats

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Yew (Taxus spp)
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Taxus species

• In addition to anticancer compounds also contain
  toxic alkaloids - taxines
• Occur in all parts of the plant except the aril
• Causes sudden death often just a few hours after
  ingestion due to cardiac arrhythmia
• Taxine inhibits sodium and calcium currents,
  blocking myocardial conduction
• Animals found dead next to yew bushes
  

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Pokeweed
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Poke - Phytolacca americana

• Roots and seeds especially toxic
• Young stems and leaves often eaten as cooked
  greens - should be avoided?
• Toxic compound - phytolaccigenin - triterpene
  saponins
• Also contains toxic alkaloids and other glycosides

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Oleander
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Oleander - Nerium oleander

• All parts of the plant are toxic
• At least 50 toxic cmpds in the plant
• Cardiac glycosides - oleandroside and nerioside
  are similar in action to digitalis
• Toxins even found in smoke from burning leaves
• Toxins absorbed by hotdogs cooked on a oleander
  branch

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Castor bean - Riccinus communis
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Ricinus communis - Castor bean

• Seeds - primary source of toxin, but the rest of
  the plant considered slightly toxic as well
• Symptoms - Stomach irritation, diarrhea,
  abdominal pain, severe dehydration, increased
  heart rate, profuse sweating, collapse,
  convulsions, death
• Major toxin is ricin, a water soluble protein,
  which is concentrated in the seed

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Ricin

• One of the most potent natural toxins known
• One seed can kill a child
• Inhibit protein sythesis by specifically and
  irreversibly inactivating eukaryotic ribosomes
• A single ricin molecule that enters the cytosol
  can inactivate over 1,500 ribosomes per minute
  and kill the cell
• Lots of possible medical applications - could
  also be used in biological warfare - weapon of
  mass destruction
• http//www.emedicine.com/emerg/topic889.htm

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Cycads

• Cycads are gymnosperms with a palm-like
  appearance
• They are found in tropical and subtropical areas
  of the world
• Large female cones with large seeds

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Cycads

• Cycads are rich in starch, which is found in the
  roots, stems, and seeds, and they have a long
  history as food as well as a medicinal plant
• However they contain toxic compounds, which must
  be removed by processing the starch before the
  flour is used
• Crushed seeds soaked in water which slowly
  dissolves the toxins out of the plant material
  over several days to weeks.

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Cycad toxins

• Cycasin and BMAA (beta-methylamino-alanine)
• Cycasin is a carcinogenic and neurotoxic
  glycoside
• BMAA is an unusual amino acid which is also
  neurotoxic and believed to act by mimicing
  glutamate and blocking glutamate receptors in the
  brain

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Cycad toxins

• Toxins cause gastrointestinal and liver problems
• Toxins also occur in the leaves of many cycads,
  and have caused poisonings in cattle and sheep
  grazing on the leaves.
• Also implicated in a number of neurological
  conditions including Guam Disease

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Guam Disease

• Following World War II, physicians found that ALS
  (amyotrophic lateral sclerosis, also known as Lou
  Gehrig's disease), was about 100 times greater
  among the native population in Guam than the rest
  of the world
• Later studies found that the incidence of
  Parkinson's disease and Alzheimer's-like dementia
  were also much higher among this population.
• Although the causes of these conditions are
  unknown, many scientists believe the neurotoxins
  in cycads may be at least partly responsible.