Poisonous Substances

Poisonous substances can be categorized by their chemical nature.  These poisonous principles are glycosides, alkaloids, oxalates, oils, minerals, nitrates, resins or resinoids, and other miscellaneous compounds.



These are complex chemical compounds that readily break down under certain conditions, yielding a sugar plus an aglycone which may be poisonous.  Glycosides are found in a variety of plants.  They are usually bitter and may be restricted to a particular plant part.  There are several types of glycosides, the most common of which are listed here.

Cyanogenetic, which yield hydrocyanic acid (prussic acid) upon break-down.  Death in these cases is usually very rapid and with few outward symptoms.  Examples: Hydrangea, Prunus, Photinia, Sorghum, and Triglochin.

Saponic, which yield saponins.  These are complex chemicals that generally cause gastric irriations.  Examples: Aesculus, Agrostemma, Daubentonia, Medicago, Phytolacca, Sesbania, and Glottidium.

Goitrogenic, which inhibits the formation of thyroid hormone.  These are found in mustards.

Irritant Oils, such as mustard oils and others, are pungent, sharp tasting compounds found mainly in the seeds.  Examples: Mustards, wild radish, Ranunculus, Actaea, and Caltha.

Coumarin, can be poisonous, but the degree of toxicity is questionable.  In some cases, coumarin forms dicoumarol, which is a hemorrhagic agent.  Examples: Aesculus and Melilotus.

Cardiac, are those which stimulate the heart.  Many different ones have been identified, most from members of the Scrophulariaceae (e.g., foxglove), Liliaceae, and Apocynaceae.



Alkaloids are complex, basic, water-insoluble compounds, some of which are very poisonous.  They are very bitter to the taste.  These mostly affect the heart and nervous system.  Examples: Aconitum, Amianthium, Argemone, Buxus, Conium, Corydalis, Crotolaria, Delphinium, Dicentra, Gelsemium, Lolium, Taxus, Veratrum, and Zigadenus.  Bulbs of Narcissus, Amaryllis, and Crocus also contain alkaloids.



Soluble and insoluble oxalates form calcium oxalate crystals, which can cause kidney damage.  Hypocalcemia is implicated.  In quantity, the oxalate produces dullness, depression, and finally death in a few hours.  Examples of plants containing oxalates include: Rheum and Rumex.  Oxalate crystals (raphides) in certain plants (Araceae, for example) may cause irritation to the mouth.



Several nonglycoside oils cause gastroenteritis, other irritant effects in the gut, and eventually death if consumed in a large enough quantity.  Examples: Chenopodium and Glechoma.



Selenium and molybdenum are two poisonous minerals taken up by plants from the soil.  They are of greatest importance in central and western United States, and are not a problem in North Carolina.  Copper, lead, cadmium, and fluorine may be deposited on foliage from air pollution or taken up by plants from contaminated soil.


Nitrate poisoning

This is fairly common and occurs most frequently when there is a sudden change in an animalís diet to plants with a high nitrate content.  It may occur from certain crop plants (oats, corn, sorghum), rye grass, vegetables (turnip tops, radish, carrot, lettuce), weeds (Amaranthus, Chenopodium, mustards, composites, nightshades), or silage or fodder with high nitrate content such as alfalfa.  Heavy fertilizing can increase nitrate contents and the potential danger.  Nitrate is reduced to nitrite, which oxidizes hemoglobin; this process causes vasodilation and sudden death.  Postmortem diagnosis of acute nitrate poisoning is by the brownish discoloration of mucous membranes and internal tissues.  The blood is chocolate colored in contrast to the bright red color indicative of cyanide poisoning.


Resins or Resinoids

These compounds are often extremely poisonous.  They are direct irritants of the nervous system.  Examples: Asclepias, Cicuta, Kalmia, Melia, and Rhododendron.


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