Cyanides, that is, hydrocyanic acid and its salts, are far from the most powerful poisons in nature. They are definitely the most famous, however, and perhaps the most used in books and movies.
The history of cyanides can be confidently traced almost from the first written sources that have come down to us. The ancient Egyptians, for example, used peach pits to obtain a deadly essence, which is simply called “peach” in the papyri on display at the Louvre.
Lethal Peach Fusion
Peach, like two and a half hundred other plants, including almonds, cherries, sweet cherries, plums, belongs to the plum genus. The seeds of the fruits of these plants contain the substance amygdalin - a glycoside, which perfectly illustrates the concept of "lethal synthesis". This term is not entirely correct, it would be more correct to call the phenomenon "lethal metabolism": in its course, a harmless (and sometimes even useful) compound is broken down by enzymes and other substances to a potent poison. In the stomach, amygdalin undergoes hydrolysis, and one glucose molecule is split off from its molecule - prunazine is formed (some of it is contained in the seeds of berries and fruits initially). Further, enzyme systems (prunazine-β-glucosidase) are included in the work, which "bite off" the last remaining glucose,after which the mandelonitrile compound remains from the original molecule. In fact, this is a meta-compound that sometimes sticks together into a single molecule, then again breaks down into its components - benzaldehyde (a weak poison with a half-lethal dose, that is, a dose that causes the death of half of the members of the test group, DL50 - 1.3 g / kg of rat body weight) and hydrocyanic acid (DL50 - 3.7 mg / kg rat body weight). It is these two substances in pair that provide the characteristic smell of bitter almonds. It is these two substances in pair that provide the characteristic smell of bitter almonds. It is these two substances in pair that provide the characteristic smell of bitter almonds.
There are no confirmed deaths in the medical literature after eating peach or apricot kernels, although cases of poisoning have been described that required hospitalization. And there is a fairly simple explanation for this: only raw bones are needed for the formation of poison, and you won't eat a lot of them. Why raw? For amygdalin to turn into hydrocyanic acid, enzymes are needed, and under the influence of high temperature (sunlight, boiling, frying) they are denatured. So compotes, preserves and "red-hot" bones are completely safe. Purely theoretically, poisoning with a tincture on fresh cherries or apricots is possible, since there are no denaturing factors in this case. But there another mechanism for neutralizing the resulting hydrocyanic acid, described at the end of the article, comes into play.
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Military background
The effectiveness of cyanide for the targeted elimination of the enemy at all times beckoned the military. But large-scale experiments became possible only at the beginning of the 20th century, when methods for the production of cyanide in industrial quantities were developed.
On July 1, 1916, the French used hydrogen cyanide against German troops for the first time in the battles near the Somme River. However, the attack failed: HCN vapors were lighter than air and quickly evaporated at high temperatures, so the "chlorine" trick with an ominous cloud spreading along the ground could not be repeated. Attempts to make hydrogen cyanide heavier with arsenic trichloride, tin chloride and chloroform were unsuccessful, so the use of cyanides had to be forgotten. More precisely, postpone - until the Second World War.
The German school of chemistry and the chemical industry at the beginning of the 20th century were unmatched. Outstanding scientists, including the 1918 Nobel laureate Fritz Haber, worked for the country's good. Under his leadership, a team of researchers at the newly created German Pest Control Society (Degesch) modified hydrocyanic acid, which has been used as a fumigant since the late 19th century. To reduce the volatility of the compound, German chemists used an adsorbent. Before use, the pellets had to be immersed in water to release the accumulated insecticide. The product was named "Cyclone". In 1922 Degesch was taken over by the Degussa Company as the sole owner. In 1926, a patent was registered for a group of developers for the second, very successful version of the insecticide - "Cyclone B", which was distinguished by a more powerful sorbent,the presence of a stabilizer, as well as an irritant that irritates the eyes - to avoid accidental poisoning.
Meanwhile, Haber has been actively promoting the idea of chemical weapons since the First World War, and many of his developments were of purely military significance. “If soldiers die in a war, then what's the difference - from what exactly,” he said. Haber's scientific and business career was confidently going uphill, and he naively believed that his services to Germany had long ago made him a full-fledged German. However, for the rising Nazis, he was primarily a Jew. Haber began to look for work in other countries, but, despite all his scientific achievements, many scientists did not forgive him for the development of chemical weapons. Nevertheless, in 1933 Haber and his family went to France, then to Spain, then to Switzerland, where he died in January 1934, fortunately for himself not having time to see for what purposes the Nazis used the Cyclone B.
Mode of operandi
Vapors of hydrocyanic acid are not very effective as a poison when inhaled, but when ingested DL50 salts are only 2.5 mg / kg body weight (for potassium cyanide). Cyanides block the last stage of the transfer of protons and electrons by the respiratory enzyme chain from oxidizable substrates to oxygen, that is, they stop cellular respiration. This process is not fast - minutes even with ultra-high doses. But the cinema, showing the rapid action of cyanides, is not lying: the first phase of poisoning - loss of consciousness - really comes after a few seconds. Agony lasts a few more minutes - convulsions, rise and fall of blood pressure, and only then comes the cessation of breathing and cardiac activity.
At lower doses, you can even track multiple periods of poisoning. First, a bitter taste and burning sensation in the mouth, salivation, nausea, headache, rapid breathing, impaired coordination of movements, increasing weakness. Later, excruciating shortness of breath joins, there is not enough oxygen to the tissues, so the brain gives the command to increase and deepen breathing (this is a very characteristic symptom). Gradually, breathing is suppressed, another characteristic symptom appears - a short inhalation and a very long exhalation. The pulse becomes more rare, the pressure drops, the pupils dilate, the skin and mucous membranes turn pink, and not turn blue or pale, as in other cases of hypoxia. If the dose is non-lethal, that's all; after a few hours, the symptoms disappear. Otherwise, there comes a turn of loss of consciousness and seizures, and then arrhythmia occurs, cardiac arrest is possible. Sometimes paralysis and prolonged (up to several days) coma develop.
Poisoned - poison
Cyanides have a very high affinity for ferric iron, which is why they rush into the cells to the respiratory enzymes. So the idea of a decoy for poison was in the air. It was first implemented in 1929 by Romanian researchers Mladoveanu and Gheorghiu, who first poisoned the dog with a lethal dose of cyanide and then rescued it with intravenous sodium nitrite. This food supplement E250 is being defrauded by all and sundry, but the animal, by the way, survived: sodium nitrite in conjunction with hemoglobin forms methemoglobin, which cyanides in the blood “peck at” better than respiratory enzymes, which still need to get inside cells.
Nitrites oxidize hemoglobin very quickly, so that one of the most effective antidotes (antidotes) - amyl nitrite, isoamyl ether of nitrous acid - just breathe in from a cotton swab, like ammonia. Later it was found that methemoglobin not only binds the cyanide ions circulating in the blood, but also unblocks the respiratory enzymes "closed" by them. The group of methemoglobin-formers, although already slower, also includes the dye methylene blue (known as "blue").
There is also a downside to the coin: when administered intravenously, nitrites themselves become poisons. So it is possible to saturate the blood with methemoglobin only with strict control of its content, no more than 25-30% of the total mass of hemoglobin. There is one more nuance: the binding reaction is reversible, that is, after a while, the formed complex will disintegrate and cyanide ions will rush into the cells to their traditional targets. So we need another line of defense, which is used, for example, cobalt compounds (cobalt salt of ethylenediaminetetraacetic acid, hydroxycobalamin is one of the B12 vitamins), as well as the anticoagulant heparin, beta-hydroxyethylmethyleneamine, hydroquinone, sodium thiosulfate.
Rasputin's casus
But the most interesting antidote is much simpler and more accessible. Back in the late 19th century, chemists noticed that cyanides are converted into non-toxic compounds when interacting with sugar (this happens especially effectively in solution). The mechanism of this phenomenon in 1915 was explained by the German scientists Rupp and Golze: cyanides, reacting with substances containing an aldehyde group, form cyanohydrins. Such groups are found in glucose, and the amygdalin mentioned at the beginning of the article is essentially cyanide neutralized by glucose.
If Prince Yusupov or one of the conspirators who joined him - Purishkevich or the Grand Duke Dmitry Pavlovich knew about this - they would not start filling cakes (where sucrose was already hydrolyzed to glucose) and wine (where glucose is also available) intended for treats to Grigory Rasputin, potassium cyanide. However, it is believed that he was not hounded at all, and the story of the poison appeared to confuse the investigation. No poison was found in the stomach of the "royal friend," but that doesn't mean anything - no one was looking for cyanohydrins there.
Glucose has its advantages: for example, it is able to restore hemoglobin. This turns out to be very useful for "picking up" the detached cyanide ions when using nitrites and other "poisonous antidotes". There is even a ready-made preparation, "chromosmon" - a 1% solution of methylene blue in a 25% glucose solution. But there are also annoying disadvantages. First, cyanohydrins are formed slowly, much more slowly than methemoglobin. Secondly, they are formed only in the blood and only before the poison enters the cells to the respiratory enzymes. In addition, eating cyanide potassium with a piece of sugar will not work: sucrose does not react with cyanides directly, it is necessary that it first breaks down into glucose with fructose. So if you are afraid of cyanide poisoning, it is better to carry an ampoule of amyl nitrite with you - crush it in a handkerchief and breathe for 10-15 seconds. And then you can call an ambulance and complain that you were poisoned with cyanide. Doctors will be surprised!
The author of the article is a toxicologist, scientific editor of the journal "Russian Pharmacies"
Alexey Vodovozov
