Template:Short description Template:Cs1 config Template:Distinguish Template:Use dmy dates Template:Chembox Solanine is a glycoalkaloid poison found in species of the nightshade family within the genus Solanum, such as the potato (Solanum tuberosum). It can occur naturally in any part of the plant, including the leaves, fruit, and tubers. Solanine has pesticidal properties, and it is one of the plant's natural defenses. Solanine was first isolated in 1820 from the berries of the European black nightshade (Solanum nigrum), after which it was named.<ref name=":1">Template:Cite journal</ref> It belongs to the chemical family of saponins.
Solanine poisoningEdit
SymptomsEdit
Solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. Symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, cardiac dysrhythmia, nightmares, headache, dizziness, itching, eczema, thyroid problems, and inflammation and pain in the joints. In more severe cases, hallucinations, loss of sensation, paralysis, fever, jaundice, dilated pupils, hypothermia, and death have been reported.<ref>Template:Cite news</ref><ref name="MP"/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Ingestion of solanine in moderate amounts can cause death. One study suggests that doses of 2 to 5 mg/kg of body weight can cause toxic symptoms, and doses of 3 to 6 mg/kg of body weight can be fatal.<ref>Executive Summary of Chaconine & Solanine Template:Webarchive</ref>
Symptoms usually occur 8 to 12 hours after ingestion, but may occur as rapidly as 10 minutes after eating high-solanine foods.Template:Citation needed
Correlation with birth defectsEdit
Some studies show a correlation between the consumption of potatoes suffering from late blight (which increases solanine and other glycoalkaloid levels) and the incidence of spina bifida in humans.Template:Citation needed However, other studies have shown no correlation between potato consumption and the incidence of birth defects.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Livestock poisoningEdit
Livestock can also be susceptible to glycoalkaloids. High concentrations of solanine are necessary to cause death to mammals. The gastrointestinal tract cannot efficiently absorb solanine, which helps decrease its strength to the mammal body.<ref name="ReferenceA">Template:Cite journal</ref> Livestock can hydrolyze solanine and excrete its contents to diminish its presence in the body.<ref name="ReferenceA"/>
Mechanism of actionEdit
There are several proposed mechanisms of how solanine causes toxicity in humans, but the true mechanism of action is not well understood. Solanum glycoalkaloids have been shown to inhibit cholinesterase, disrupt cell membranes, and cause birth defects.<ref>Template:Cite book</ref> One study suggests that the toxic mechanism of solanine is caused by the chemical's interaction with mitochondrial membranes. Experiments show that solanine exposure opens the potassium channels of mitochondria, increasing their membrane potential. This, in turn, leads to Ca2+ being transported from the mitochondria into the cytoplasm, and this increased concentration of Ca2+ in the cytoplasm triggers cell damage and apoptosis.<ref>Template:Cite journal</ref> Potato, tomato, and eggplant glycoalkaloids like solanine have also been shown to affect active transport of sodium across cell membranes.<ref name="mendel">Template:Cite journal</ref> This cell membrane disruption is likely the cause of many of the symptoms of solanine toxicity, including burning sensations in the mouth, nausea, vomiting, abdominal cramps, diarrhea, internal hemorrhaging, and stomach lesions.<ref name=autogenerated5>Template:Cite journal</ref>
BiosynthesisEdit
Solanine is a glycoalkaloid poison created by various plants in the genus Solanum, such as the potato plant. When the plant's stem, tubers, or leaves are exposed to sunlight, it stimulates the biosynthesis of solanine and other glycoalkaloids as a defense mechanism so it is not eaten.<ref name=autogenerated3>Template:Cite journal</ref> It is therefore considered to be a natural pesticide.Template:Citation needed
Though the structures of the intermediates in this biosynthetic pathway are shown, many of the specific enzymes involved in these chemical processes are not known. However, it is known that in the biosynthesis of solanine, cholesterol is first converted into the steroidal alkaloid solanidine. This is accomplished through a series of hydroxylation, transamination, oxidation, cyclization, dehydration, and reduction reactions.<ref>Template:Cite journal</ref> Specifically, solanidine formation involves sequential hydroxylation, transamination, and cyclization reactions<ref name=":1" />.The solanidine is then converted into solanine through a series of glycosylation reactions catalyzed by specific glycosyltransferases.<ref name=autogenerated3 />
Plants like the potato and tomato constantly synthesize low levels of glycoalkaloids like solanine. However, under stress, such as the presence of a pest or herbivore, they increase the synthesis of compounds like solanine as a natural chemical defense.<ref>Template:Cite journal</ref> This rapid increase in glycoalkaloid concentration gives the potatoes a bitter taste, and stressful stimuli like light also stimulate photosynthesis and the accumulation of chlorophyll. As a result, the potatoes turn green, and are thus unattractive to pests.<ref>Template:Cite journal</ref> Other stressors that can stimulate increased solanine biosynthesis include mechanical damage, improper storage conditions, improper food processing, and sprouting.<ref>Template:Cite journal</ref> The largest concentration of solanine in response to stress is on the surface in the peel, making it an even better defense mechanism against pests trying to consume it.<ref>Template:Cite journal</ref>
SafetyEdit
Suggested limits on consumption of solanineEdit
Toxicity typically occurs when people ingest potatoes containing high levels of solanine. The average consumption of potatoes in the U.S. is estimated to be about 167 g of potatoes per day per person.<ref name=autogenerated5 /> There is variation in glycoalkaloid levels in different types of potatoes, but potato farmers aim to keep solanine levels below 0.2 mg/g.<ref name=":0">Template:Cite book</ref> Signs of solanine poisoning have been linked to eating potatoes with solanine concentrations of between 0.1 and 0.4 mg per gram of potato.<ref name=":0" /> The average potato has 0.075 mg solanine/g potato, which is equal to about 0.18 mg/kg based on average daily potato consumption.<ref name=autogenerated1>Template:Cite journal</ref>
Calculations have shown that 2 to 5 mg/kg of body weight is the likely toxic dose of glycoalkaloids like solanine in humans, with 3 to 6 mg/kg constituting the fatal dose.<ref name=autogenerated2>Template:Cite journal</ref> Other studies have shown that symptoms of toxicity were observed with consumption of even 1 mg/kg.<ref name=autogenerated5 />
Storage of potatoesEdit
Various storage conditions can have an impact on the level of solanine in potatoes. Glycoalkaloid levels increase when potatoes are exposed to light because light increases synthesis of glycoalkaloids like solanine.<ref name=":0" /> Potatoes stored in a dark place avoid increased solanine synthesis. Potatoes that have turned green due to increased chlorophyll and photosynthesis are indicative of increased light exposure and are therefore associated with high levels of solanine.<ref name=autogenerated2 /> Synthesis of solanine is also stimulated by mechanical injury because glycoalkaloids are synthesized at cut surfaces of potatoes.<ref name=":0" /> Storage of potatoes for extended periods of time has also been associated with increased solanine content.<ref>Template:Cite journal</ref> A study found that the solanine levels in Kurfi Jyoti and Kurfi Giriraj potatoes increase solanine levels by 0.232 mg/g and 0.252 mg/g respectively after being poorly stored in a heap.<ref>Haseena, R., Ganapathy, S., Pandiarajan, T., & Amirtham, D. (2019). Effect of storage methods on solanine content of potato tubers. Journal of Pharmacognosy and Phytochemistry, 8(6), 1677–1679.</ref>
Effects of cooking on solanine levelsEdit
Most home processing methods like boiling, cooking, and frying potatoes have been shown to have minimal effects on solanine levels. For example, boiling potatoes reduces the α-chaconine and α-solanine levels by only 3.5% and 1.2% respectively, but microwaving potatoes reduces the alkaloid content by 15%.<ref>Template:Cite journal</ref> Deep frying at Template:Convert also does not result in any measurable change. Alkaloids like solanine have been shown to start decomposing and degrading at approximately Template:Convert, and deep-frying potatoes at Template:Convert for 10 minutes causes a loss of ~40% of the solanine.<ref name="mendel"/> Freeze-drying and dehydrating potatoes has a very minimal effect on solanine content.<ref>Template:Cite book</ref><ref name=autogenerated4>Template:Cite journal</ref>
The majority (30–80%) of the solanine in potatoes is found in the outer layer of the potato.<ref name=autogenerated4 /> Therefore, peeling potatoes before cooking them reduces the glycoalkaloid intake from potato consumption. Fried potato peels have been shown to have 1.4–1.5 mg solanine/g, which is seven times the recommended upper safety limit of 0.2 mg/g.<ref name=":0" /> Chewing a small piece of the raw potato peel before cooking can help determine the level of solanine contained in the potato; bitterness indicates high glycoalkaloid content.<ref name=":0" /> If the potato has more than 0.2 mg/g of solanine, an immediate burning sensation will develop in the mouth.<ref name=":0" />
Recorded human poisoningsEdit
Though fatalities from solanine poisoning are rare, there have been several notable cases of human solanine poisonings. Between 1865 and 1983, there were around 2000 documented human cases of solanine poisoning, with most recovering fully and 30 deaths.<ref>Template:Cite book</ref> Because the symptoms are similar to those of food poisoning, it is possible that there are many undiagnosed cases of solanine toxicity.<ref>Template:Cite journal</ref>
In 1899, 56 German soldiers fell ill due to solanine poisoning after consuming cooked potatoes containing 0.24 mg of solanine per gram of potato.<ref>Template:Cite book</ref> There were no fatalities, but a few soldiers were left partially paralyzed and jaundiced. In 1918, there were 41 cases of solanine poisoning in people who had eaten a bad crop of potatoes with 0.43 mg solanine/g potato with no recorded fatalities.<ref name=autogenerated4 />
In Scotland in 1918, there were 61 cases of solanine poisoning after consumption of potatoes containing 0.41 mg of solanine per gram of potato, resulting in the death of a five-year old.<ref>Template:Cite journal</ref>
A case report from 1925 reported that 7 family members who ate green potatoes fell ill from solanine poisoning two days later, resulting in the deaths of the 45-year-old mother and 16-year-old daughter. The other family members recovered fully.<ref name=autogenerated1 /> In another case report from 1959, four members of a British family exhibited symptoms of solanine poisoning after eating jacket potatoes (baked potatoes) containing 0.5 mg of solanine per gram of potato.Template:Citation needed
There was a mass solanine poisoning incident in 1979 in the U.K., when 78 adolescent boys at a boarding school exhibited symptoms after eating potatoes that had been stored improperly over the summer.<ref>Template:Cite journal</ref> Seventeen of them ended up hospitalized, but they all recovered. The potatoes were determined to have between 0.25 and 0.3 mg of solanine per gram of potato.Template:Citation needed
Another mass poisoning was reported in Canada in 1984, after 61 schoolchildren and teachers showed symptoms of solanine toxicity after consuming baked potatoes with 0.5 mg of solanine per gram of potato.<ref>Template:Cite journal</ref>
In potatoesEdit
.jpg){kind=link}
Potatoes naturally produce solanine and chaconine, a related glycoalkaloid, as a defense mechanism against insects, disease, and herbivores. Potato leaves, stems, and shoots are naturally high in glycoalkaloids.Template:Citation needed
When potato tubers are exposed to light, they turn green and increase glycoalkaloid production. This is a natural defense to help prevent the uncovered tuber from being eaten. The green colour is from chlorophyll, and is itself harmless. However, it is an indication that increased level of solanine and chaconine may be present. In potato tubers, 30–80% of the solanine develops in and close to the skin, and some potato varieties have high levels of solanine.Template:Citation needed
Some potato diseases, such as late blight, can dramatically increase the levels of glycoalkaloids present in potatoes. Tubers damaged in harvesting and/or transport also produce increased levels of glycoalkaloids; this is believed to be a natural reaction of the plant in response to disease and damage.Template:Citation needed
Also, the tuber glycoalkaloids (such as solanine) can be affected by some chemical fertilization. For example, different studies have reported that glycoalkaloids content increases by increasing the concentration of nitrogen fertilizer.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Green colouring under the skin strongly suggests solanine build-up in potatoes, although each process can occur without the other. A bitter taste in a potato is another – potentially more reliable – indicator of toxicity. Because of the bitter taste and appearance of such potatoes, solanine poisoning is rare outside conditions of food shortage. The symptoms are mainly vomiting and diarrhea, and the condition may be misdiagnosed as gastroenteritis. Most potato poisoning victims recover fully, although fatalities are known, especially when victims are undernourished or do not receive suitable treatment.<ref>Template:Cite journal</ref>
The United States National Institutes of Health's information on solanine strongly advises against eating potatoes that are green below the skin.<ref name="MP">Template:MedlinePlusEncyclopedia</ref>
In other plantsEdit
Fatalities are also known from solanine poisoning from other plants in the nightshade family, such as the berries of Solanum dulcamara (woody nightshade).<ref>Template:Cite journal</ref>
Template:VanchorEdit
Some, such as the California Poison Control Center, have claimed that unripe tomatoes and tomato leaves contain solanine. However, Mendel Friedman of the United States Department of Agriculture contradicts this claim, stating that tomatine, a relatively benign alkaloid, is the tomato alkaloid while solanine is found in potatoes. Food science writer Harold McGee has found scant evidence for tomato toxicity in the medical and veterinary literature.<ref>Template:Cite news</ref>
In popular cultureEdit
Dorothy L. Sayers's short story "The Leopard Lady", in the 1939 collection In the Teeth of the Evidence, features a child poisoned by potato berries injected with solanine to increase their toxicity.Template:Citation needed
See alsoEdit
ReferencesEdit
External linksEdit
- a-Chaconine and a-Solanine, Review of Toxicological Literature
- Template:MedlinePlusEncyclopedia – "Green tubers and sprouts"