Plant toxins pyrrolizidine alkaloids

Insects have evolved mechanisms to tolerate plant toxins. Such mechanisms enable them to use a plant as a food source that is avoided by other herbivores, and provides the herbivore with its own ecological niche.9 For example, insects may prevent accumulation of detrimental alkaloids in the hemolymph by efficient excretion. Larvae of Spodoptera littoralis (Lepidoptera, Noctuidae) feed freely on plants containing pyrrolizidine alkaloids that are rapidly excreted and only transiently detectable in the hemolymph. Even pyrrolizidine alkaloids directly injected into the hemolymph are efficiently excreted.48 The same has been observed... 

In the West Indies especially, pyrrolizidine alkaloid toxicity is a continuing problem, as plants containing pyrrolizidine alkaloids such as Heliotropium, Senecio, and Crotolaria species are used in traditional medicine to make herbal teas. Chronic exposure to low doses of these alkaloids causes liver cirrhosis, and it is estimated that these alkaloids account for one-third of the cirrhosis cases detected at autopsy in Jamaica (see Chapter 6 for more details of these natural toxins). 

Because 1,4-dichlorobenzene is a liver toxin, it probably can interact with other chemicals that are liver toxicants. These toxicants are many, and include ethanol, halogenated hydrocarbons (chloroform, carbon tetrachloride, etc ), benzene, and other haloalkanes and haloalkenes. In addition, 1,4-dichlorobenzene toxicity may also be exacerbated by concurrent exposure with acetaminophen, heavy metals (copper, iron, arsenic), aflatoxins, pyrrolizidine alkaloids (from some types of plants), high levels of vitamin A, and hepatitis viruses. Such interactions could either be additive or S5mergistic effects. 

The pyrrolizidine alkaloids, found in the genus Senecio and a number of other plant genera, are plant toxins of environmental interest that have been implicated in a number... 

Chemical-induced liver injury is encountered in a variety of circumstances. Some natural toxins such as the peptides of Amanita phalloides, the pyrrolizidine alkaloids, the toxin of the cycad nut, and other plant toxins are hazards posed by the environment. Some mycotoxins are ingested unknowingly because of feed contamination due to climatic conditions favorable to fungal growth. Other circumstances of exposure to hepatotoxins include contamination of water supply with cyanobacterial toxins, which led to the tragic death of 60 patients in a hemodialysis clinic in Brazil in 1996 (Jochimsen et al, 1998). 

There is no evidence of pyrrolizidine alkaloids in Eupatorium rugosum (white snakeroot) but this plant also has poisonous properties, which are attributed to an unstable toxin called tremetol. Transfer from cow s milk to humans can produce a condition known as milk sickness, including trembles, weakness, nausea and vomiting, prostration, delirium, and even death. 

When a family of toxins is weUknown, like the pyrrolizidine alkaloids [1], it is highly interesting to screen suspected plants for their presence when poisoning is suspected in animals and there may be some residues in food, even in animals which did not present any disorder. 

Pyrrolizidine alkaloids (PAs) constitute a class of plant toxin associated with disease in humans and animals. They are found in a wide variety of plant species in the world and it is estimated that 3% of the world s flowering plants contain toxic pyrrolizidine alkaloids. 

Another important group of plant toxins are pyrrolizidine alkaloids (PAs) (71) of which even a single administration can be fatal (72). Poisonings by PAs are prevalent in Southern Africa (73), with a number of cases recorded for chil en (74). 

H. Hepatic failure. A variety of dmgs and toxins may cause hepatic injury (Table 1-29). Mechanisms of toxicity include direct hepatocellular damage (eg. Amanita phalloides mushrooms [see p 273]), metabolic creation of a hepato-toxic intermediate (eg, acetaminophen [p 66] or carbon tetrachloride [p 154]), or hepatic vein thrombosis (eg, pyrrolizidine alkaloids see Plants, p 309). 

Pyrrolizidine alkaloids are the leading plant toxins that have deleterious effects on the health of humans and animals. Over 360 different pyrrolizidine alkaloids are found in approximately 3% of the world s flowering plants. These noxious natural products are primarily restricted to the Boraginaceae (many genera), Asteraceae (tribes Senecionae and Eupatoriae), Fabaceae (mainly the genus Crotalaria), and... 

Pyrrolizidine alkaloids plants, metabolism and toxicity. J Nat Toxins 8 5-116... 

Pyrrolizidine alkaloids poison animals grazing on toxic wild plants and those fed contaminated feed, causing economic losses. They poison humans through deliberate consumption of certain foods and herbal medicines and through consumption of food contaminated by wild plants, such as via transport of the toxins by bees into honey. Analytical methods are required for different purposes - to detect the presence of pyrrolizidine alkaloids, to quantify the total level of the toxins, or to measure the quantity of individual compounds. The task is made more challenging by the variety of PAs, their widespread nature and their different forms. Analytical methods are based on color reactions, enzyme linked immunosorbent assays (ELlSAs), spectroscopy, and the full range of chromatographic techniques. A lack of reference standards and... 

Pyrrolizidine alkaloids (PAs) are toxins produced as secondary metabolites by a very large number of plants widespread across the plant kingdom. They are... 

Stegehneier BL, Edgar JA, Colegate SM, Gardner DR, Schoch TK, Coulombe RA, Molyneux RJ (1999) Pyrrolizidine alkaloid plants, metabolism and toxicity. J Nat Toxins 8 95-116... 

Pyrrolizidine alkaloids are poisonous to humans and cause losses in hvestock, especially grazing animals. Humans are exposed to pyrrolizidine alkaloids through consumption of plants containing these toxins, contaminated staple products, herbal teas or medicines, and dietary supplements (Fu et al. 2004). Poisoning by pyrrolizidine alkaloids is endemic in India, Jamaica and parts of Africa. Native American and Hispanic populations in western... 

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