Pyrrolizidine alkaloid

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Skeletal formula of retronecine, a pyrrolizidine alkaloid found in the Common groundsel (Senecio vulgaris) and comfrey (Symphytum spp.)

Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Pyrrolizidine alkaloids are produced by plants as a defense mechanism against insect herbivores. More than 660 PAs and PA N-oxides have been identified in over 6,000 plants, and about half of them exhibit hepatotoxicity.[1] They are found frequently in plants in the Boraginaceae, Asteraceae, Orchidaceae and Fabaceae families; less frequently in the Convolvulaceae and Poaceae, and in at least one species in the Lamiaceae. It has been estimated that 3% of the world’s flowering plants contain pyrrolizidine alkaloids.[2] Honey can contain pyrrolizidine alkaloids,[3][4] as can grains, milk, offal and eggs.[5] To date (2011), there is no international regulation of PAs in food, unlike those for herbs and medicines.[6][7]

Unsaturated pyrrolizidine alkaloids are hepatotoxic, that is, damaging to the liver.[8][9] PAs also cause hepatic veno-occlusive disease and liver cancer.[10] PAs are tumorigenic.[11] Disease associated with consumption of PAs is known as pyrrolizidine alkaloidosis.

Of concern is the health risk associated with the use of medicinal herbs that contain PAs, notably borage leaf, comfrey and coltsfoot in the West, and some Chinese medicinal herbs.[11]

Some ruminant animals, for example cattle, showed no change in liver enzyme activities or any clinical signs of poisoning when fed plants containing pyrrolizidine alkaloids.[12] Yet Australian studies have demonstrated toxicity[13] Sheep, goats and cattle are much more resistant and tolerate much higher PA dosages, thought to be due to thorough detoxification via PA-destroying rumen microbes.[14] Males react more sensitively than females and fetuses and children.[15]

PA is also used as a defense mechanism for some organisms such as Utetheisa ornatrix. Utetheisa ornatrix caterpillars obtain these toxins from their food plants and use them as a deterrent for predators. PAs protect them from most of their natural enemies. The toxins stay in these organisms even when they metamorphose into adult moths, continuing to protect them throughout their adult stage.[16]

Ecology[edit]

Many plants contain pyrrolizidine alkaloids, and in turn there are many insects which consume the plants and build up the alkaloids in their bodies.[17] For example, male queen butterflies utilize pyrrolizidine alkaloids to produce pheromones useful for mating.[18] The butterfly Danaus chrysippus is known to obtain pyrrolizidine alkaloids in their diet and store these chemicals, making them toxic and unpalatable to predators.[19] Greta oto, the glasswing butterfly, uses pyrrolizidine alkaloids for both toxicity in the adult moth and pheromone production in the male butterfly. The garden tiger moth also stores these compounds as a caterpillar, using them for larval (through the use of spines) and adult defense (in the form of a spray and bad taste).[20]

Plants species containing pyrrolizidine alkaloids[edit]

The effect of PAs in humans, that is PAILDs,[27] of epidemic proportions was recorded after a long field-level epidemiological investigation in the northern region of Ethiopia- Tigray.

Classification[edit]

One classification is based on the substitution pattern of the pyrrolizidine ring. This part of the structure is normally referred to as necine bases.

The three largest groups are based on the three necine bases platynecine, heliotridine and retronecine.


References[edit]

  1. ^ Radominska-Pandya, A (2010). "Invited Speakers". Drug Metabolism Reviews. 42 (S1): 1–2. doi:10.3109/03602532.2010.506057. PMID 20842800. 
  2. ^ Smith, L. W.; Culvenor, C. C. J. (1981). "Plant sources of hepatotoxic pyrrolizidine alkaloids". J. Nat. Prod. 44 (2): 129–15. doi:10.1021/np50014a001. PMID 7017073. 
  3. ^ Kempf, M; Reinhard, A; Beuerle, T (Jan 2010). "Pyrrolizidine alkaloids (PAs) in honey and pollen-legal regulation of PA levels in food and animal feed required". Mol Nutr Food Res. 54 (1): 158–68. doi:10.1002/mnfr.200900529. PMID 20013889. 
  4. ^ Edgar, John A.; Roeder, Erhard; Molyneux, Russell J. (2002). "Honey from Plants Containing Pyrrolizidine Alkaloids: A Potential Threat to Health". J. Agric. Food Chem. 50 (10): 2719–2730. doi:10.1021/jf0114482. 
  5. ^ "Pyrrolizidine alkaloids in Food" (PDF). Archived from the original (PDF) on 2009-10-14. 
  6. ^ Coulombe, Roger A. Jr (2003). "Pyrrolizidine alkaloids in foods". Advances in Food and Nutrition Research. 45: 61–99. PMID 12402679. 
  7. ^ German Commission E monographs
  8. ^ "Foodborne Pathogenic Microorganisms and Natural Toxins Handbook: Pyrrolizidine Alkaloids". Bad Bug Book. United States Food and Drug Administration. Retrieved 2009-07-11. 
  9. ^ Schoental, R.; Kelly, JS (April 1959). "Liver lesions in young rats suckled by mothers treated with the pyrrolizidine (Senecio) alkaloids, lasiocarpine and retrorsine". The Journal of Pathology and Bacteriology. 77 (2): 485–495. doi:10.1002/path.1700770220. PMID 13642195. 
  10. ^ Schoental, R (1968). "Toxicology and Carcinogenic Action of Pyrrolizidine Alkaloids" (PDF). Cancer Research. 28: 2237–2246. 
  11. ^ a b Fu, P.P.; Yang, Y.C.; Xia, Q.; Chou, M.C.; Cui, Y.Y.; Lin, G. (2002). "Pyrrolizidine alkaloids-tumorigenic components in Chinese herbal medicines and dietary supplements". Journal of Food and Drug Analysis. 10 (4): 198–211. 
  12. ^ Skaanild, M.T.; Friis, C.; Brimer, L. (2001). "Interplant alkaloid variation and Senecio vernalis toxicity in cattle". Veterinary and Human Toxicology. 43 (3): 147–151. 
  13. ^ Noble, J.W.; Crossley, J.; Hill, B.D.; Pierce, R.J.; McKenzie, R.A.; Debritz, M.; Morley, A.A. (1994). "Pyrrolizidine alkaloidosis of cattle associated with Senecio lautus". Australian Veterinary Journal. 71 (7): 196–200. doi:10.1111/j.1751-0813.1994.tb03400.x. PMID 7945096. 
  14. ^ Wiedenfeld, H.; Edgar, J. (2010). "Toxicity of pyrrolizidine alkaloids to humans and ruminants". Phytochemistry Reviews. 
  15. ^ Wiedenfeld, H.; Edgar, J. "Toxicity of pyrrolizidine alkaloids to humans and ruminants". Phytochemistry Reviews. 2010: 1–15. 
  16. ^ Conner, W.E. (2009). Tiger Moths and Woolly Bears—behaviour, ecology, and evolution of the Arctiidae. New York: Oxford University Press. p. 1-10.
  17. ^ Nishida, R; Schulz, S; Kim, C. S; Fukami, H; Kuwahara, Y; Honda, K; Hayashi, N (1996). "Male sex pheromone of a giant danaine butterfly,Idea leuconoe". Journal of Chemical Ecology. 22 (5): 949. doi:10.1007/BF02029947. PMID 24227617. 
  18. ^ Scott, James A. (1997). The Butterflies of North America. Stanford, California: Stanford University Press. pp. 228–232. 
  19. ^ Edgar, J. A.; Cockrum, P. A.; Frahn, J. L. (1976-12-01). "Pyrrolizidine alkaloids inDanaus plexippus L. andDanaus chrysippus L". Experientia. 32 (12): 1535–1537. doi:10.1007/bf01924437. ISSN 0014-4754. 
  20. ^ Macel, Mirka (2011-03-01). "Attract and deter: a dual role for pyrrolizidine alkaloids in plant–insect interactions". Phytochemistry Reviews. 10 (1): 75–82. doi:10.1007/s11101-010-9181-1. ISSN 1568-7767. 
  21. ^ Wiedenfeld, H; Andrade-Cetto, A (2001). "Pyrrolizidine alkaloids from Ageratum houstonianum Mill". Phytochemistry. 57 (8): 1269–71. doi:10.1016/S0031-9422(01)00192-3. PMID 11454357. 
  22. ^ Broch-Due, Å. I.; Aasen, A. J. (1980). "Alkaloids of Anchusa officinalis L. Identification of the Pyrrolizidine Alkaloid Lycopsamine". Acta Chem. Scand. B34: 75–77. 
  23. ^ a b c d e f g h The MERCK Veterinary Manual, Table 5 Archived 2010-11-17 at the Wayback Machine.
  24. ^ Wood, Matthew. "The Book of Herbal Wisdom: Using Plants As Medicines." Berkeley CA. North Atlantic Books. 1997.
  25. ^ Rizk A. M. Naturally Occurring Pyrrolizidine Alkaloids. CRC Press, Boca Raton, FL, USA. 1990.
  26. ^ Yeong M. L.; et al. (1990). "Hepatic veno-occlusive disease associated with comfrey ingestion". Journal of Gastroenterology and Hepatology. 5 (2): 211–214. doi:10.1111/j.1440-1746.1990.tb01827.x. PMID 2103401. 
  27. ^ "Pyrrolizidine Alkaloid Induced Liver Diseases", cited in Chiu, C; Buttke, D; Welde, G; Luce, R; Debela, A; Bitew, A; Bayleyegn, T; Vagi, S; Murphy, M; Woldemichael, D; Seboxa, T; Libanos, G. G; Beyene, Z; Hawaria, Y. G; Jimma, D; Tareke, I; Rentz, D; Martin, C (2013). "Evaluation of the Pyrrolizidine Alkaloid Induced Liver Disease (PAILD) Active Surveillance System in Tigray, Ethiopia". Online Journal of Public Health Informatics. 5 (1): e167. PMC 3692817Freely accessible. 

23. https://www.cdc.gov/nceh/stories/Ethiopia.html, Investigating Liver disease in Ethiopia

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