Plant Toxins in Toxicology

Plant Toxins

• Plant toxins are explored within the field of toxicology

Learning Goals

• Understanding the risks associated with plant usage is important
• Comprehending the chemical basis for plant interactions is essential
• Learning chemical groups/metabolites commonly involved in plant toxicity is part of toxicology studies
• Knowledge of plant toxins aids in predicting/detecting plant toxicity

Plant-Related Toxicity

• Paracelsus stated all things are poison, and it is the dosage that differentiates a poison from a remedy
• Theophrastus von Hohenheim is also known as Paracelsus, and Philippus Aureolus Theophrastus Bombastus von Hohenheim

Definition of Plant Toxins/Phytotoxins

• Plants detrimentally affect the health of humans or animals when consumed normally or under unique circumstances like restricted diets or severe hunger
• Phytotoxins are active agents that induce toxic effects
• Phytotoxins are secondary plant metabolites
• Plants synthesize secondary plant metabolites causing toxins

Phytotoxins vs. Phytopoisons

• Plant toxins are chemical metabolites, such as peptides or proteins
• Plant toxins can cause diseases by interacting with body tissues and enzymes
• Some plant toxins cause minor discomfort/pain, while others can be deadly
• Poisons are substances absorbed through the skin/gut, causing chemical reactions
• Poisons refer to harmful substances like corrosives, carcinogens, and pollutants

Phytotoxins/Phytopoisons Information

• Phytotoxins serve as defense agents agains pests or herbivores
• Agents are classified into two primary categories which are constitutive and induced
• In 399 BCE, Socrates was sentenced to death for corrupting the youth of Athens and disrespecting the city's gods
• Hemlock (Conium maculatum) was a standard form of capital punishment
• Coniine, a poisonous polyketide-derived alkaloid, can be found in Hemlock

Local Plant Toxins

• Trial by ordeal involved ingesting poisonous plants as a judiciary process
• Physostigma venenosum, also known as Calabar beans, and Tanghinia venenifera are poisonous plants
• Strophanthus hispidus and cardiac glycosides are arrow poisons
• Tephrosia vogelii, Adenia lobata, Balanites aegyptiaca, and saponins are fish poisons

General Groups of Plant Poisons

• Pyrrolizidine alkaloids include Crotalaria spp and Heliotropium spp
• Unsaturated nucleus pyrrolizidine alkaloids are toxic while saturated are non-toxic
• Pyrrolizidine alkaloids are associated with hepatotoxicity upon consumption
• Lectins are plant proteins, mitogenic & hemagglutinating agents, and Leguminosae

Saponins and Diterpenes

• Saponins causes severe gastrointestinal irritation
• Saponins cause intense abdominal cramping and haematemesis
• Systemic saponin exposure can lead to hypotension and tachycardia
• Wild yams contain saponins
• Diterpenes are known for their irritant properties
• Diterpene esters are highly irritant to mucosal surfaces

Cyanogenetic Glycosides

• Cyanogenetic glycosides are present in kernels of fruits
• Hydrolysis of these compounds results in the release of hydrogen cyanide (HCN)
• HCN is rapidly absorbed from the upper gastrointestinal tract
• HCN poisoning associates with respiratory failure

Furanocoumarins

• Furanocoumarins are predominantly in the families of Umbelliferae, Rutaceae, Moraceae, and Leguminosae
• Furanocoumarins are phototoxic
• Severe phototoxic reactions are reported after using bergamot oil in topical preparations

Abrus Precatorius

• Abrus means graceful and precatorius means to pray
• Seeds contain abrin (jequiritin) which is lectin or hemagglutin similar to ricin physiologically
• Abrin is the main toxic component

Blighia Sapida

• Fleshy arils of ripe fruits are eaten after parboiling and frying
• Consuming the fruit leads to vomiting known as hypoglycaemia sickness
• Hypoglycin A and B are two toxic principles

Dieffenbachia and Euphorbia

• Dieffenbachia sequine Schott and D. picta Schott are known as dumbcane
• Dumbcane is commonly grown as a houseplant
• When ingested, dumbcane can cause severe corrosive burns in the mouth, esophagus and stomach since it contains Calsium Oxalate
• Euphorbia spp produces a latex
• Latex is highly irritating and often produces vesication, emesis and purgation when in contact,
• The esters of tetracycline diterpenoids: Phorbol, are resposible

Jatropha curcas and J. Multifida

• Jatropha curcas and J. multifida are also refered to as physic nut
• Jatropha curcas and J. multifida are closely related to the castor oil plant
• Jatropha curcas and J. multifida contain purgative oils and a toxic lectin

Lantana Camara

• A plant with aromatic leaves, orange or bright red flowers, and dark blue or black fruits
• When ingested, can cause vomiting, diarrhoea and respiratory distress
• The components in Lantana Camara that cause this effect include lantadene A and B

Solanum Spp

• Solanum Spp includes S. nigrum and S. tuberosum
• They both contain toxic steroidal glycoalkaloids
• The toxicity varies based on the stage of development and genetic factors
• When Glycoalkaloids are consumed, they may cause stupefaction and dullness

Thevetia Peruviana

• Has a digitalis-like effect
• Contains cardiac glycosides

Argemone Mexicana

• Argemone oil poisoning include vomiting, diarrhea,nausea, swelling of limbs, erythema, pitting edema, breathlessness, etc
• They contain Benzophenanthridine alkaloids, sanguinarine and dihydrosanguinarine
• In extreme cases glaucoma and even death from a cardiac arrest can happen

Ricinus Communis

• Acute poisioning in humans are caused by oral ingestion of castor beans, five to twenty could prove fatal to an adult
• Physical symptoms can include nausea, diarrhea, tachycardia, hypotension and even seziures for a week
• Ricin, a lectin is responsible for the toxicity of Ricinus Communis