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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. 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.〔Smith, L. W.; Culvenor, C. C. J. Plant sources of hepatotoxic pyrrolizidine alkaloids. J. Nat. Prod. 1981, 44, 129-15〕 Honey can contain pyrrolizidine alkaloids,〔Kempf M, Reinhard A, Beuerle T.,Pyrrolizidine alkaloids (PAs) in honey and pollen-legal regulation of PA levels in food and animal feed required. Mol Nutr Food Res. 2010 Jan;54(1):158-68.〕〔Edgar, John A., Erhard Roeder, and Russell J. Molyneux, J. Agric. Food Chem., Vol. 50, No. 10, 2002, "Honey from Plants Containing Pyrrolizidine Alkaloids: A Potential Threat to Health"〕 as can grains, milk, offal and eggs.〔PYRROLIZIDINE ALKALOIDS IN FOOD http://www.foodstandards.gov.au/_srcfiles/tr2.pdf〕 To date (2011), there is no international regulation of PAs in food, unlike those for herbs and medicines.〔Coulombe, Roger A., Jr., "Pyrrolizidine alkaloids in foods" ''Advances in Food and Nutrition Research'' Volume 45, 2003, Pages 61-99〕〔German Commission E monographs〕 Unsaturated pyrrolizidine alkaloids are hepatotoxic, that is, damaging to the liver. PAs also cause hepatic veno-occlusive disease and liver cancer.〔Schoental, R., "Toxicology and Carcinogenic Action of Pyrrolizidine Alkaloids", ''Cancer Research'' No.28, pp.2237-2246, November 1968 ()〕 PAs are tumorigenic.〔Fu, P.P., Yang, Y.C., Xia, Q., Chou, M.C., Cui, Y.Y., Lin G., "Pyrrolizidine alkaloids-tumorigenic components in Chinese herbal medicines and dietary supplements", ''Journal of Food and Drug Analysis'', Vol. 10, No. 4, 2002, pp. 198-211 ()〕 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.〔 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. Yet Australian studies have demonstrated toxicity 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.〔Wiedenfeld H., Edgar J., "Toxicity of pyrrolizidine alkaloids to humans and ruminants" Phytochemistry Reviews (1-15) 2010〕 Males react more sensitively than females and fetuses and children.〔Wiedenfeld H., Edgar J. "Toxicity of pyrrolizidine alkaloids to humans and ruminants" Phytochemistry Reviews 2010 (1-15)〕 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.〔Conner, W.E. (2009). Tiger Moths and Woolly Bears—behaviour, ecology, and evolution of the Arctiidae. New York: Oxford University Press. p. 1-10.〕 ==Ecology== (詳細はMale sex pheromone of a giant danaine butterfly,Idea leuconoe )〕 For example, male Queens utilize pyrrolizidine alkaloids to produce pheromones useful for mating. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pyrrolizidine alkaloid」の詳細全文を読む スポンサード リンク
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