Notes phytochemist. Potatoes. Part Three Bulba Fugu or SOLANIN

... a potato is quite capable of coping with a person.
unknown folk source

The most common “potato threat” is considered to be solanine, which “forms in greened potatoes” and another phytomeat is dedicated to him, the consequences of his use, as well as the ways of salvation from it. Since the information on the Internet is very fragmented, and even it is simply not there - I tried to write in such a way that I got an exhaustive tutorial (it might even get to Wikipedia someday, although Habr would rather become Wikipedia) . Therefore, I advise anyone to go under the cut faster than anyone who cares for their health. At the same time, you will find out why the Islamic fundamentalists' manuals teach you to use potatoes as chemical weapons of mass destruction and why pregnant women need to be very careful when using “green potatoes” or even abandon this option in order to avoid the occurrence of neurological abnormalities in the fetus. UPD : and pro without the danger of sprouted potatoes.


Recently, along with such stable expressions as "antioxidants" or "anti-nutrients", the concept of phytoalexins is used in world phytochemistry. In this way, researchers are trying to reduce all herbal components that have antimicrobial and often antioxidant properties of substances synthesized de novo plants, which quickly accumulate in the areas of infection with pathogens and are the plant "immune response." As a rule, these substances are inhibitors of a wide spectrum of action with a very diverse chemical structure and specific features inherent in certain plant species. In general, phytoalexins are divided into several classes: terpenoids, glycosteroids, alkaloids. Many researchers are in favor of expanding the definition of "phytoalexin" and the inclusion in this concept of all phytochemical components that are used by plants for protection.

Solanine

In English, the Solanaceae family (the same family, which includes our beloved potatoes, tomatoes, eggplants, sweet peppers, but also tobacco, mandragora, belladonna, henbane and dope) is also called nightshades , literally "night shadows." The appearance of this name is sometimes attributed to the fact that even the ancient Romans actively used the plants of this family to prepare various poisons. This makes sense, since in my opinion, the most powerful weapon of plants is their alkaloids. In essence, alkaloids are common chemical nitrogenous compounds, most often in plants acting as a secondary metabolite. In plants of the Solanaceae family, the most bioactive are the so-called. tropane alkaloids (scopolamine, atropine, hyoscyamine, nicotine), and precisely because of their bioactivity, these compounds have been used most often since ancient times as poisons (belladonna poison or henbane poison, the psychoactive effect of dope, mandrake and tobacco).

To the note : it is scopolamine , an alkaloid contained in such plants as scopoly, belladonna, henbane, dope, at the beginning of the 20th century was proposed as a “truth serum”, a disinhibiting effect was caused by the introduction of so-called state of "twilight consciousness." This is certainly not quite the effect, but nevertheless ...

Solanine belongs to the class of alkaloids of plants of the Solanaceae family, and solanine is present mostly in potatoes.

Note : you can often find the statement that solanine is also found in tomatoes. This is not true. Tomatoes contain “something similar” - an alkaloid tomin (or lycopersicin ). It is tomato and its derivative, tomato, that play a major role in confronting a tomato in front of a fungal, microbial, insecticidal (because of the presence of tomato, the tomato “does not take” the Colorado potato beetle) by threat (well, from snails and goats of all kinds, too, by itself, not bad protection ). Therefore, most of the alkaloid is concentrated in the leaves and inflorescences, approximately 1/5 falls into the fruit (and when ripe it gradually decreases to a certain indicator depending on the variety). Why I decided to mention tomato. First, because it is almost always confused with solanine, although tomato is ten times less toxic than solanine (LD ₅₀ when administered orally about 500 mg / kg body weight). And secondly, it illustrates what every phytosterol aspires to "- when in contact with cholesterol in any product, it instantly binds it into an insoluble complex and removes it from the body without digestion. In general, if the hands reach the phyto-consideration of tomatoes, I will tell you more about this interesting alkaloid.

We return to the solanine. This glycoalkaloid was discovered as far back as 1820 in Black Nights ( Solanum nigrum ) berries, after which it was named. It belongs to the chemical family of saponins. I once wrote about saponins in one of my banana notes:

Saponins are substances that are glycosidic compounds with a steroid (C ₂₇ ) or triterpenoid (C ₃₀ ) (139) sapogenic core with one or more carbohydrate side chains. Due to their amphiphilic character and surface-active properties, saponins are excellent foaming agents, forming a very stable foam.

Where does solanine come from in potatoes

Under natural conditions in the potato, the cycle of alkaloids constantly occurs; during the growth of the plant, tens and hundreds of different compounds are biosynthesized. Naturally, there are many alkaloids among them, including the already mentioned solanine. Solanine together with its related compound, haconin, is synthesized in potatoes from acetyl-coenzyme A and cholesterol. The scheme by which all this happens can be seen below (the image is clickable).



The mentioned alkaloids are constantly synthesized as a kind of “depot protection” against insects, fungi, microorganisms and herbivores.

Minute lyrics. Here I look at these biosynthesis schemes and I understand that chemistry should strive for just such a type. Necessary compounds, peptides, etc. - are synthesized in plants, not in flasks. And the chemist's laboratory is some kind of experimental field, and not a laboratory room in which you can hang an ax. I don’t know how quickly my dreams will come true, but my favorite D. Cronenberg ’s weapon inside the living reactor was already growing in his Existence ( eXistenZ ) ...

OK, continue. The greatest accumulation of protective alkaloids is observed in those parts of the plant that are most at risk of being eaten (ie, in parts located above the ground) —in leaves, stems, shoots, and inflorescences. Under normal (= "greenhouse") conditions, only a small amount (relative to the amount in the remaining parts) of the alkaloids is synthesized in tubers.

But the situation changes dramatically when the tuber is pulled out of the ground, they begin to be transported and stored in anthropogenic conditions. At the beginning of the article I wrote about phytoalexins, as substances that start to generate plants when they get into unfavorable conditions (uncomfortable) environmental conditions or are exposed to damage (mechanical, fungal, bacterial, etc.). The plant's response to such factors is reflected in an increase in the production of glycoalkaloids (sometimes several times). Actually, the whole mechanism of biosynthesis works only for “war”.

The most common "folk" sign of the presence of elevated solanine content is the green color of the potato.


IMPORTANT : although the green color of the potato, which was exposed to light radiation, is only the color of chlorophyll (which, by the way, is actively used as a dye in food products, like cheese , and completely harmless). Solanin, which is synthesized in such tubers (after all, a bright light = “tuber on the surface” => include protection against eating = “synthesize killer doses of solanine and hakonin) in general does not have color and it is impossible to notice it with the naked eye. As in the case of a banana - this is just a color indication of a possible (but not mandatory) increase in the level of glycoalkaloids. Those. Each of the processes (accumulation of solanine and greening of potatoes) can quite do without the other.

By the way, Ukrainian researchers experienced this inconsistency before others and began to create a biosensor on for the rapid detection of glycoalkaloids, exploiting the anticholinesterase activity of glycoalkaloids. True, despite the fact that more than 10 years have passed, “things are still there”. So - we work in the old manner.

Continuing the theme of greening, we can safely say that “and my grandmother was right again,” when she advised me to cut the peel on green potatoes to white flesh. Indeed, in potato tubers from 30 to 80% of the solanine / hakonin fraction content falls on the peel and the layer of pulp under it is about 7-10 mm (i.e., on the skin, bark and vascular ring). To better understand what to trim - below is a graphic illustration.


In addition to sunlight, in the role of aggressive factors of external influence, leading to the "release of corned beef" include fungal diseases (all kinds of "rot", etc.), as well as damage to tubers during harvesting and transportation. By the way, a small life hack. Saponins are generally known for having a very bitter taste, which frightens herbivores even in small doses. This is completely true for solanine. Those. if a bitter taste is observed in a green potato, such a vegetable is only ejected (even it is absolutely impossible to feed the cattle). It is bitterness that is considered the most reliable criterion for the presence of solanine (although I would partially argue, since some short-chain peptides formed during incomplete enzymatic hydrolysis of potato proteins and which can be found in raw potatoes also give a bitter taste, but these are chemical particulars, in general - bitter potatoes will definitely be harmful to the body).

UPD : the Solairw user in his comment touched upon the fact that I initially missed from attention, about “potatoes with sprouts”, i.e. sprouted potatoes, "about the danger of which is also often said."


When storing potatoes, the process is so-called. aging, during which some biochemical processes take place slowly but surely in the tuber. If the external conditions (temperature, humidity, light) are within the physiological "potato" rate , then there is no noticeable deterioration in the quality of the tuber. Yes, there is a gradual decrease in the starch content and total sugar, yes, there is a proteolysis of patatin potato protein. But, for example, the content of antioxidant components practically does not change, and all protein compounds are inactivated by heat treatment (during cooking / frying). A completely different situation arises if, due to improper storage conditions, the tubers are exposed to cold / heat shock (stress) or excessive light exposure. In response to such factors unfavorable to the tuber, the defense mechanism is activated and the potato begins to grow green and germinate. As a rule, this is accompanied by enhanced biosynthesis of solanine / haconin glycoalkaloids, and they are localized mainly in those same shoots (read “shoots take a hit”). What does this mean for the average consumer? And all the same. In principle, everything said in the article is equally applicable for sprouted potatoes and for non-sprouted. It is just worth removing the sprouts together with the greened skin, thus minimizing the possible contact with poisonous alkaloids and then just boil / fry the potatoes as if nothing had happened. Of course, such potatoes have slightly deteriorated taste (less starch / sugars), but then the glycemic index will be lower. Most people consider sprouted potatoes as harmful and immediately throw them away, but I note that it is much less harmful than not sprouted, but damaged by various types of rot. The fact that the problem really exists, confirms the attention to such a respected organization as the US Department of Agriculture (the nutrients of which I constantly use when writing my articles). Every year, hundreds of tons of sprouted potatoes are thrown into the United States, which is still quite possible to be eaten without much harm by simply processing it correctly. In the form of confirmation under the spoiler a piece of the USDA methodical “potato” recommendations.


Due to the high prevalence of potatoes (and therefore the availability of skills to work with them among consumers), cases of solanine poisoning are quite rare under normal conditions (i.e., when there is enough food). The danger manifests itself in areas of humanitarian disasters, armed conflicts, etc. where food shortages. But even in such cases, the removal of 10–15 mm of peel from each tuber will relieve the “gourmet” from a large dose of glycoalkaloids (the rest will be removed by heat treatment, but more on that below).

Biological effects and symptoms of poisoning

About what solanin arises from and why he does it, I told. It would be logical to assume that the reason for its deadly harm should be explained. This will be true for both saponins and other surfactants (surfactants). In their action, glycoalkaloids put pressure on two diseased sites - they destroy cell membranes and inhibit the enzyme acetylcholinesterase (even in rats they induce destruction of the liver, but “this is not accurate”).

The mechanism of action on the cell membrane is shown in the picture (the image is clickable)


By their poisonous effect on the cell membrane, glycoalkaloids are required to form stable stoichiometric (1: 1) complexes with cholesterol, which in turn is one of the most important cellular substances (and not just “cholesterol plaques”, as someone might think). After entering the body, the alkaloid part (aglycone) of solanine is reversibly associated with sterols, which form a double lipid layer (read about this layer in the last banana note , and a reminder picture under the spoiler)


When the density of glycoalkaloids in the membrane reaches a certain level, the “sugar” carbohydrate heads of our “potato poisons” will begin to electrostatically attract each other and form already stable and absolutely irreversible glycoalkaloid-sterol complexes. In the place of sterols lost to the organism, sterols from the outer side of the double lipid layer that are destroyed by alkaloids will be pulled into sterols from the inner side (to “mend” the gap that has formed) ”. As a result, roughly foam bubbles form in the double lipid layer, its integrity and performance are impaired. The cell in which the membrane is destroyed - perishes. For example, when glycoalkaloids enter the intestine and disruption of the double lipid layer of the membrane of epithelial cells, macromolecules of everything else (including the alkaloids themselves) begin to flow into the blood. In fact, glycoalkaloids destroy one of the main cellular protective barriers of the body. In addition, the damaged membrane changes its potential and reduces the active transport of sodium ions, which affects, for example, cardiac activity. Solanine is able to "open" potassium channels of mitochondria, increasing their membrane potential. This, in turn, leads to the transport of Ca ²⁺ from the mitochondria to the cytoplasm, and such an increase in the concentration of calcium ions in the cytoplasm causes cell damage and apoptosis .

The second poisoning effect is the inhibitory effect on the enzyme acetylcholinesterase . Here is what Wikipedia says about this:

Acetylcholinesterase inhibitors (organophosphate insecticides, DFP, sarin, soman and V-gases, fasciculin and some other snake venom peptides) are powerful toxins whose effects on the human body usually lead to death from cramps in the respiratory muscles.

As some probably know from school biology (Soviet times) acetylcholine is an important neutrotransmitter in the human body, and it is he who is responsible for transmitting electrical signals from neurons to muscles. Acetylcholine is released by neurons and acts on the sheath of the muscle fiber, causing depolarization and contraction (or relaxation, to whom that is more pleasant). In order for the muscle to be reduced again, it is necessary that the released acetylcholine is already cleaved by the enzyme acetylcholinesterase. If there is no such enzyme (or it is "frozen" = inhibited), then acetylcholine gradually accumulates in synapses and muscles, completely disrupting the transmission of signals from nerves to muscles. In principle, the action is simple, and quickly fatal. There are truth studies that suggest that glycoalkaloids, in addition, reversibly inhibit another enzyme, butyrylcholinesterase , which may be responsible for cell growth. But what kind of cell growth can we talk about when the transmission of nerve signals is disturbed ...

A rather unpleasant effect is described in the article . The authors found an epidemiological correlation between the congenital malformations of the fetal nervous system (anencephaly and vertebral artery cleft) in pregnant women and the use of potatoes with an increased content of glycoalkaloids by women.

The main symptoms of simple solanine poisoning are mainly gastrointestinal manifestation, i.e. vomiting, diarrhea, abdominal pain (therefore, there are cases when poisoning with solanine was taken for gastroenteritis) + in acute poisoning, symptoms typical for poisoning with ARS with acetylcholinesterase inhibitors can also be added (as well as fever, rapid pulse, low blood pressure, rapid breathing, etc.). Estimates of LD ₅₀ toxicity vary, it is believed that a dose of 2–5 mg / kg body weight causes toxic manifestations, and 5–10 mg / kg may be fatal. There is even an unspoken guide, which recommends the concentration of glycoalkaloids = <200 mg / kg wet weight when developing new potato varieties.

There is a story that the mention of solanine was found in many textbooks for terrorists seized by the FBI in Afghanistan, and Islamic terrorists can use solanine as a weapon of mass destruction. In the seized benefits described available methods for obtaining poisons.

In principle, not so far from the truth, it remains only to learn how to “ask” potatoes to generate solanine for the order ...

Note: it will be wrong to show only the dark side of the force. Therefore, I note that some acetylcholinesterase inhibitors are even synthesized artificially for use in the treatment of Alzheimer's disease, dementia with Lewy calves, myasthenia, can be used as an antidote for anticholinergic poisoning (cyclodol, dimedrol, taren). Comparatively recently, studies have been conducted on cell cultures that have shown high efficacy (comparable to the anticancer drug adriamycin) solanin and hokanin in inhibiting the growth of cancer cells in colon and liver tumors in humans. The anti-cancer effect of glycoalkaloids was also noted when using cell cultures of cervical cancer, lymphoma, and stomach cancer. Moreover, the use of two or more glycoalkaloids allowed to achieve a stable synergistic effect. There is also a work where it has been shown that the use of haconin reduces the number of metastases in lung cancer and may in the long run create a new direction of chemotherapy.

So how to escape?

Whose fault, I hope, is clear. But what to do? And asking permission from the potato to eat it, as in the old days, people asked permission from the tree to cut it down to build a house. Moreover, it is better to tell the tuber how to spend the strength that you will get from the starch. Whether on a good deal the force will go. And having eaten potatoes, you feel, as you feel, the tuber, as it were understood by you, the test “learn your eloquence for plants”. Treat the potato with respect, and it will not poison you with solanine.

But seriously, it is very likely that the attentive reader has already partly understood from the text of the article how to protect themselves from being poisoned by solanin & hokanin. First, you need to choose potatoes with minimal mechanical damage (it’s not for nothing that people in shops intuitively buy clean, well-groomed potatoes from Israel, and don’t take a Belarusian one, which is not only expensive, but also scratched, potholed, rotten) signs of fungal and bacterial diseases. Secondly, if there are suspicions of the presence of harmful glycoalkaloids - just peel the skin to a depth of 1-1.5 cm (of course, nothing can remain in the end from small potatoes), this will remove up to 80% of the potato alkaloids.

Important! : The popular methods of heat treatment (cooking, frying, baking), on the contrary, have a weak and “with varying success” effect on the content of solanine and its comrades. For example, cooking potatoes reduces the level of α-haconin and α-solanine by only 3.5% and 1.2%, respectively (but at the same time, cooking in a microwave reduces the content by 15%). Deep roasting at 150 ° C does not lead to any tangible changes, significant destruction of glycoalkaloids begins only at ~ 170 ° C, and frying at 210 ° C for 10 minutes leads to a loss of 40% of harmful alkaloids (another thing is then there will be such potatoes). Freeze drying or other types of dehydration does not have a significant effect on the content of solanine in general.

Third, the toxicity of alkaloids in food can also be affected by the products in its (food) composition. After all, you can combine them so that solanine and his ilk adsorb or at least turn into an inactive compound. Glycoalkaloids are generally hard to digest in the body, the presence of fiber interferes with absorption (read dietary fiber). Folic acid, glucose-6-phosphate and Nicotinamide adenine dinucleotide ( NAD ) bind haconin into non-toxic complexes. The most active form of solanine & haconin is the β-form (see picture above), respectively, all that contribute to the hydrolysis of this type of glycoalkaloids reduces toxicity (and this may be low pH or exposure to mold fungi Aspergillus niger (!!)).

By the way, there is such an interesting direction in food business (to write an article about which Alexey Shukayev long ago asked me) as food pairing .

FoodPairing is a method for determining combinations of products that are best combined with each other in terms of taste (i.e., having a common flavor component). The approaches currently used combine products from the point of view of digestion. Метод использует ВЭЖХ, газовую хроматографию и другие лабораторные методы для анализа продуктов питания и поиска общих для них химических компонентов.

Obviously, a cook with such skills is not a “graduate of a culinary technical school,” but rather a chemist and even a nanotechnologist (as with the Fugu fish, when people have been learning how to cook it for years). Although I fully admit that there is a cook without the right background, but with God's spark, who, not knowing any chemistry and biology there, can, on a whim, prepare “ambrosia and nectar”, which grant health and cure for any ailments. Namely, this should, in my opinion, be any food (about functional food look in the banana article ).

And fourth. At the very extreme case I will say that in case of acute poisonings with the mentioned alkaloids, cholinesterase reactivators are introduced into the body.. They help restore cholinesterase activity, providing an antidote effect. In the first stage of poisoning, dipyroxime is used . In case of pronounced disorders of mental activity (lethargy, coma), a centrally acting drug, isonitrosin, is additionally administered . At the third stage of poisoning, the combined use of dipyroxime with isonitrosin is necessary.

On this all, take care of yourself and be careful! And to be fully prepared - read Habr (# phytochemist notes) :-)

PS I can not fail to mention the fact voiced in the comments ( one and two times ) by the user minamoto . Let's call it the phenomenon of " potato Lenope". A variety with this name was introduced to the US market in 1967 and already in 1970, these potatoes had to be massively withdrawn from crop rotation. The reason for this was mass poisoning caused by several times too high content of potato glycoalkaloids (16–35 mg / 100 g fresh). masses of potato varieties Lenope versus 3–18 mg / 100 g of fresh mass in potatoes of other varieties.) Interestingly, the variety was bred using traditional breeding methods (this fact is often used as counter-arguments in conversations with opponents of GMO fiction). some torye researchers, exceptionally high levels of glycoalkaloids were due to "impurities" gene wild Peruvian potato, accidentally caught in the plant due to cross-breeding. Genetic engineering makes it possible to avoid such a risk of accidental introduction of new genes,all used "components" are carefully selected and validated. Among certain advantages that have arisen due to the “Lenope phenomenon”, we can mention at least mandatory testing of all new varieties (both GMOs and traditional breeding) for the content of glycoalkaloids in them.

Sergey Besarab ( Siarhei V. Besarab )