Plant Toxins

definition

Last update: 22/05/2026

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Plant toxins are biosynthesized toxic compounds produced by plants for natural self-defense against herbivore animals, micro-organisms, insects and other plants. They naturally occur in food, feed, weeds and ornamental plants. The botanical and chemical diversities are very rich, including:

  • Alkaloids (e.g., Pyrrolizidine Alkaloids (PAs), Tropane Alkaloids (TAs), Quinolizidine Alkaloids (QAs), Glycoalkaloids, Opium Alkaloids), 
  • Glycosides (e.g., Cyanogenic Glycosides (CGs) and Hydrocyanic acid and cyanide from CGs), 
  • Terpenoids (e.g., Cannabinoids, Grayanotoxins (GTXs), triptolide, tutin),
  • Nitrophenanthrene derivatives (e.g, aristolochic acid) 
  • and alkenylbenzenes (e.g, trans-anethole, methyl eugenol, myristicin, safrole), which are more often considered phytochemicals and are generally regulated based on their use as flavorings or food supplement ingredients rather than as plant toxins.
ToxinsBiosynthetic origin
Pyrrolizidine AlkaloidsMainly found in Boraginaceae, Asteraceae, Orchidaceae and Fabaceae families. Most studied are Senecionine-, Lycopsamine-, Heliotrine- and Monocrotaline- types.
Tropane AlkaloidsNaturally occur predominantly in Brassicaceae, Solanaceae and Erythroxylaceae families. Most studied are Scopolamine and Atropine.
Quinolizidine AlkaloidsPresent in the legume family, especially in the genus Lupinus (lupins). Most studied are angustifoline, anagyrine, cytisine, lupanine, lupinine, isolupanine, sparteine, 13α-hydroxylupanine, multiforine and thermopsine.
GlycoalkaloidsOccur in nightshade crops such as potatoes (Solanum tuberosum), tomatoes (Solanum lycopersicum), and eggplants (Solanum melongena) with the highest levels in the non-edible parts of the plant.
Opium alkaloidsOccur in Papaver somniferum L. (Papaveraceae), mainly in latex of seed capsules; poppy seeds may be contaminated during harvest. Poppy seeds are  used in bakery products or teas.Most studied are morphine, codeine, thebaine and papaverine and noscapine.
Cyanogenic glycosides/ Hydrocyanic acid and cyanidesMore studied are Amygdalin, Linamarin, Linustatin, Lotaustralin, Neolinustatin, Prunasin.Amygdalin are found in bitter almonds, apricot kernels, peach, plum, cherry seeds, apple seeds and linamarin in cassava (Manihot esculenta), lima beans and flaxseed.
CannabinoidsA family of more than 100 molecules. The 2 most regulated cannabinoids are Δ9-Tetrahydrocannabinol (THC) the main psychoactive compound, and cannabidiol (CBD), which is non-psychoactive. THC is mainly formed when THCA is exposed to heat (decarboxylation).
Erucic acidErucic acid is a fatty acid that can be found in vegetable oils as rapeseed oil and mustard oil.
GrayanotoxinsMainly produced by Rhododendron species and other plants in the Ericaceae family.Honey containing grayanotoxins is also known as “Pontic honey”, “mad honey” or “bitter honey”.
Aristolochic acidsA family of compounds in the plant, collectively called aristolochic acids (AAs) in Aristolochia clematitis.The two most common and biologically significant forms are Aristolochic acid I (AAI) and Aristolochic acid II (AAII). 
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