Poisonous and Allergy Plants Notes

Poisonous and Allergy Plants

Introduction

  • Overview of poisonous plants, including their history and uses.
  • Discussion of why plants produce poisons.
  • Identification of poisonous plants in the wild and at home.
  • Explanation of allergy plants.

Plants and Humans

  • Humans learned about plant properties through trial and error, distinguishing edible, medicinal, and poisonous plants.
  • Poisonous plants were used for hunting, leading to the origin of the word "toxic" from arrow poison.
  • In Renaissance Europe, poisons were used to eliminate political enemies.

Poisonous Plants

  • Poisonous plants are widespread.
  • Plants produce poisons as defense mechanisms.
  • They are chemical factories that produce compounds to discourage herbivores.
  • Timing and placement of chemicals manipulate animal behavior. For example, tomatine in green tomatoes discourages herbivores while seeds are still immature.
  • Some animals develop toxicity from plants:
    • Monarch butterflies: Caterpillars feed on milkweed, making the butterflies toxic to birds.
  • Some plants are poisonous to other plants for territorial competition, known as allelopathy.
    • Allelopathy: Biochemical interactions between plants.

Types of Toxic Compounds

  • Poisonous plants contain various toxic compounds:
    • Alkaloids
    • Cardiac glycosides
    • Cyanide
    • Other compounds

Alkaloids

  • Bitter compounds containing nitrogen.
  • Examples:
    • American or Canadian Yew: Contains taxine, causing sudden death.
    • Buttercups: Contain ranunculin, causing diarrhea and vomiting.
    • Boxwood: Contains buxene, causing convulsions and death.
    • Poison hemlock: Contains coniine, causing paralysis of the diaphragm and death by asphyxiation.
      • Greek philosopher Socrates was forced to drink hemlock.
    • Strychnine: Found in strychnine tree seeds, native to India, causing convulsions and death.
      • Used as rat poison.
      • Cleopatra tested it on servants to decide on a suicide method.

Cardiac Glycosides

  • Oleander: A common ornamental shrub containing nerioside and oleandroside.
    • A single leaf can be lethal to an adult.
    • Lethal if used to grill hotdogs.
  • Lily of the Valley: Contains convallarin, causing irregular heartbeat, similar to Digitalis.
  • Rhododendron and Azaleas: Common ornamental plants with poisonous compounds, including nectar.
    • Contain grayanotoxins, stimulating and then blocking nervous regulation of the heart.

Cyanide

  • Found in the seeds of the rose family, such as apples, apricots, peach pits, and leaves.
  • Cyanide levels are very low in the fruit but high in leaves and seeds.
  • Cassava needs extensive soaking to remove cyanide.
  • Lima beans may contain cyanide, but American varieties are bred to have low, safe levels.

Ricin

  • Castor bean: Contains ricin, a very toxic protein.
    • A single seed can kill a child.
    • One of the most potent compounds.
    • Oil was used as a purgative, but it did not contain the protein, and the seed has a tough protective coat.
    • Ricin is a lectin or toxalbumin, which causes blood cells to aggregate.
    • Castor bean is a common houseplant.

Ricin News

  • 2014 Ricin Case at Georgetown University
    • A student created ricin from castor beans after getting the idea from the TV show "Breaking Bad."
    • The ricin produced was seven times as powerful as cobra venom.
  • Recent News: Arrest in case of ricin letters sent to White House, Texas
    • September 21, 2020: A woman was arrested for sending an envelope containing ricin to the White House and law enforcement agencies in Texas.

Other Poisonous Plants

  • Wisteria: Contains wistarine, causing death (2 seeds).
  • Mistletoe: Contains viscotoxin, which can be fatal if eaten in large amounts.
  • Pokeweed: Roots and berries cause respiratory depression.

Poisonous Plants at Home

  • Philodendron and Dumbcane: Contain calcium oxalate crystals that cause painful burning and swelling of the mouth and throat, making breathing difficult.

Milder Discouragement

  • Some plants are poisonous but generally not lethal.
    • Oxalic acid: Found in rhubarb leaves, paralyzes the vocal cords. Stalks are safe to eat.
    • Saponins: Such as tomatine in tomatoes and solanine in potatoes, cause nausea, vomiting, and diarrhea.
      • Solanine is present in most parts of the potato plant except the tubers.
      • Green potatoes (exposed to sunlight) can cause poisoning.
  • Tannins
    • Tannins in leaves, stems, and roots make plants unpalatable, bitter, or astringent.
    • Tannins are present in tea leaves, making them dark.

Allergens

  • Contact Dermatitis:Caused by allergens like poison ivy and poison oak.
    • They contain urushiol, an oil that triggers the body's defenses, causing reddening, warming, and bubbling of the skin.
    • "Leaves of three, let it be."

Allergens - Food and Pollen

  • Food allergies: Compounds in certain foods can produce an immune reaction in some people.
    • Symptoms include swelling, redness, rash, hives, pain, diarrhea, or even asthma.
    • Common allergens: peanuts, soybeans, wheat, nuts, strawberries, citrus, etc.
  • Hay fever: Allergies caused by plant pollen, such as ragweed, and is wind-pollinated.
    • More than 35 million Americans suffer from it.
    • Antihistamines are used to treat the symptoms.

Peanut Allergy

  • Peanut allergy occurs when your immune system mistakenly identifies peanut proteins as something harmful.
  • When you have direct or indirect contact with peanuts, your immune system releases symptom-causing chemicals into your bloodstream.

Human Uses of Plant Poisons

  • Natural crop protection.
  • Selective poisons of pests, safe insecticides (can kill insects or fish but are safe for mammals).
  • Medicines in smaller doses.
  • Poison arrows and darts in some societies for hunting.
    • Use of curare by Amazon tribes.

Important Lessons

  • Plants have effective chemical defense mechanisms for protection.
  • Many household plants are very poisonous.
  • Poisons are also present in some food plants.
  • 99% of carcinogens in food are present naturally, not sprayed on.
  • Location is important - toxicity depends on what part of the plant is eaten.
  • Timing - whether fruit is ripe or unripe is what makes it edible vs. poisonous.
  • Avoid a diet focused on one single food to reduce the level of any one toxin.