Glycoalkaloid

Phytoalexins are low molecular weight compounds produced in plants as a defense mechanism against microorganisms. They do, however, exhibit toxicity to humans and other animals in addition to microbes (30). Coumarins, glycoalkaloids, isocoumarins, isoflavonoids, linear furanocoumarins, stilbenes, and terpenes aU. fall into the category of phytoalexins (31). Because phytoalexins are natural components of plants, and because their concentration may increase as a response to production and management stimuli, it is useful to recogni2e the possible effects of phytoalexins in the human diet. 

Assessment of whether a chemical has the potential to cause adverse effects in humans arises usually from direct observation of an effect in animals or humans, such as the acute poisoning episodes that have occurred when potatoes contain high levels of glycoalkaloids. Epidemiological studies have also been used to infer a possible relationship between intake of a particular type of food, or constituent of that food, and the potential to cause an adverse effect. Such observations led to the characterisation of the aflatoxins as human carcinogens. However, natural toxic substances that occur in plant foods have often been identified through observations in animals, particularly farm animals. It was observations of adverse effects in farm animals that led to the further characterisation of the phytoestrogens and the mycotoxins. In other instances, the concern arises from the chemical similarity to other known toxins. 

Wszelaki AL, Delwiche JF, Walker SD, Liggett RE, Scheerens JC and Kleinhenz MD (2005) Sensory quality and mineral and glycoalkaloid concentrations in organically and conventionally grown redskin potatoes (Solanum tuberosum). Journal of the Science of Food and Agriculture, 85, 720-726. 

Friedman M (2002), Tomato glycoalkaloids role in the plant and in the diet , J Agric Food Chem, 50, 5751-5778. 

Friedman M and McDonald G M (1997), Potato glycoalkaloids chemistry, analysis, safety and plant physiology , Crit Rev Plant Sci, 16, 55-132. 

Sanford L L, Deahl K L, Sinde S L and Ladd Jr T L (1992), Glycoalkaloid content in tubers from Solanum tuberosum populations selected for potato leafhopper resistance , Am Potato J, 69, 693-703. 

The fruit of a number of solanaceous plants, including tomato Lycopersicon esculentum), potato Solanum tuberosum) and eggplant Solarium melongena esculentum), have cholinesterase-inhibiting effects (Krasowski et al. 1997). They contain solanaceous glycoalkaloids o-solanine and o-chaconine, which are triglycosides of solanidine, a steroidal alkaloid derived from cholesterol. They are the only plant chemicals known to inhibit both acetlycholinesterase and butyrylcholinesterase, both in vitro and in vivo. 

Levels of solanaceous glycoalkaloids can be significant, occasionally causing toxicity in humans and livestock. Symptoms of potato poisoning include gastrointestinal disturbances, apathy, drowsiness, mental confusion, visual disturbances, dizziness, hallucinations, and trembling. Symptoms may perist 2-24 hours after consumption, and one recent outbreak showed reduced butyrylcholinesterase levels six days later, which then returned to normal in 4 to 5 weeks. 

Steroidal Alkaloids and Steroidal Glycoalkaloids Norditerpenoid Alkaloids Pyrrolizidine Alkaloids Indolizidine and Polyhydroxy Alkaloids Tropane Alkaloids Glycosides... 

Keukens EAJ et al (1995) Molecular basis of glycoalkaloid induced membrane disruption. Biochim Biophys Acta 1240 216... 

Stine KJ et al (2006) Interaction of the glycoalkaloid tomatine with DMPC and sterol mono-layers studied by surface pressure measurements and brewster angle microscopy. J Physical Chem B 110 22220... 

Glycosides of compounds with a triterpenoid origin include saponins, cardiac glycosides, and glycoalkaloids such as solanine (in potatoes). 

The Indians of the Peruvian Altiplano eat potatoes with a dip of clay and a mustard-like herb. They say the clay removes the bitter taste and prevents stomach pains or vomiting after eating large amounts of potatoes. The people who eat clay intend detoxication. This may explain how Indians started to utilize and domesticate wild potatoes. Indeed, experiments have shown that four different types of edible clay adsorb the glycoalkaloid tomatine under simulated... 

Clay eating probably was extremely important in human evolution it enabled hominids who did not use fire to eat plants with toxic antifeedants. However, the glycoalkaloids of the potato are heat stable and insoluble in water. Domestication of tomatoes and potatoes probably went hand in hand with clay eating. Johns (1986) suggested that geophagy is the most basic human detoxification technique with behavior antecedents that are prehominid. ... 

Cipollini, M. L. and Levey, D. J. (1997). Antifungal activity ofSolanum fruit glycoalkaloids implications for frugivory and seed dispersal. Ecology 78,799-809. 

Renwick, J. H., Glaring, W. B., Earthy, M. E., etal. (1984). Neural-tube defects produced in Syrian hamsters by potato glycoalkaloids. Teratology 30,371-381. 

Tomatoes, a major food source for humans, accumulate a variety of secondary metabolites including glycoalkaloids (1). These metabolites protect against the adverse effects of pathogens and predators, including fungi, bacteria, viruses, and insects. 

ID TOCSY was used extensively in the proton assignment and structural characterization of glycoalkaloids, such as saponins [29, 35, 37, 38], where the assignment of both the steroidal and the carbohydrate parts of the molecules can benefit from the sequential connectivity information provided by this technique. 

Fig. 1A-C. Examples of different classes of saponins A the triterpenoid saponin avenacin A-1 from roots of Avena spp B the steroidal saponin gracillin, from Costus speciosus C the steroidal glycoalkaloid a-tomatine from tomato (Lycopersicon spp.)...

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