Since ancient times, people have used herbal ingredients to relieve pain and get rid of diseases and ailments. However, the study of precisely the component composition, the isolation of those compounds that have such an effect, became possible only with the wide and massive development of chemistry as a science, that is, starting from the 17th century.

It was then that nitrogen-containing organic compounds were discovered in the bowels of plant organisms, and today even in some animals, which gave such a wide therapeutic effect. Since 1819, the general name for this group of substances is alkaloids. Proposed by V. Meisner, pharmacist and doctor.

What is an alkaloid?

At present, it is generally accepted that an alkaloid is a cyclic compound containing one or more nitrogen atoms in the ring or side chain and, by its chemical nature, exhibits the properties of a weak alkali, like ammonia. Previously, it was said about the definition of these substances as derivatives of the nitrogenous base of pyridine. However, a number of compounds of this group were later discovered, which showed that such an interpretation is not entirely correct and does not cover the entire variety of alkaloids.

For the first time this substance was obtained and studied in 1803 by the scientist Derson. It was morphine, derived from opium. Subsequently, independently of each other, many scientists discovered a number of complex ones from plant materials. So there was an idea that the alkaloid is a substance of predominantly natural origin. Formed only in plants.

Chemical composition of molecules

By their chemical nature, these substances are nitrogen-containing organic compounds that contain nitrogen atoms in complex heterocycles interconnected by different types of bonds and interactions.

They are isolated from plants as salts of certain acids:

• apple;
• wine;
• oxalic;
• acetic and others.

If a pure substance is separated from the salt, then the alkaloid can be obtained in the form of a solid crystalline powder, or it can be in the form of a liquid structure (nicotine). In both cases, it is an alkaline compound that exhibits the corresponding chemical properties.

That is, the chemistry of alkaloids is known and studied. For example, methods have been identified by which they can be isolated from plant materials. They are based on the solubility of alkaloid salts in water, since in their pure form these compounds are almost insoluble in water, but they do it perfectly in organic solvents.

A number of reactions by which the isolation and study of such compounds takes place are called alkaloid reactions.

1. Precipitation. Reactions based on the formation of an insoluble alkaloid salt that precipitates. This can be done if the following components are used: tannin, picric acid, phosphotungstic or molybdic acid.
2. Precipitation. Reactions based on the formation of complex complex salts with the participation of alkaloid compounds. Reagents: potassium iodide or bismuth.
3. Coloring. During these reactions, the form of the alkaloid changes and it becomes noticeable in the general composition. The principle of action is the effect on heterocycles, the appearance of color. Reagents: nitric acid, sulfuric acid, (II) freshly precipitated.

Often, staining reactions do not give accurate results, since the heterocyclic composition of alkaloids is similar to that of protein molecules. Therefore, they give the same effect.

Classification of alkaloids

What categories all known compounds of this group are divided into, determines the type of alkaloid, its chemical structure. Such a classification was created by Academician A.P. Orekhov and is based on the type and structure of the heterocycle with nitrogen atoms in them.

1. Pyrrolidine, pyrrolizidine and their derivatives. This group includes such alkaloids as platifillin, sarracin, senecifylline and others. The structure is based on complex five-membered heterocycles connected to each other, which include a nitrogen atom.
2. Piperidine and pyridine, their derivatives. Representatives: anabasin, lobelin. The basis is six-membered complex cycles with nitrogen.
3. Quinolizidine and its compounds. This group includes: pahikarpin, thermopsin and others. The chemical basis in complex six-membered heterocycles connected to each other and nitrogen.
4. Quinoline derivatives - quinine, echinopsin.
5. An important group of very common alkaloids are the isoquinoline compounds. Salsalin, morphine and papaverine are widely used in medicine. This also includes alkaloids in barberry plants, machka and celandine.
6. Tropane derivatives are chemically very complex in structure - hyoscyamine, atropine, scopolamine. The structure is represented by complexly condensed, intertwined pyrrolidine and piperidine rings.
7. Indole and its compounds - reserpine, strychnine, vinblastine and others. A complex combination of five- and six-membered rings with nitrogen atoms in the structure.
8. The main alkaloid in the food industry and medicine is caffeine from tea leaves and seeds of the cola plant. Refers to purine derivatives - complex compounds from different heterocycles and several nitrogen atoms in the composition.
9. Ephedrine and its compounds - spherophysin, colchicine and colchamine. The chemical name of ephedrine, reflecting its complex structure, phenylmethylaminopropanol is a complex organic aromatic alcohol.
10. Recently, it is customary to isolate some substances of the steroid group - corticosteroids and sex hormones - into alkaloids.

Physical properties

The main properties of this group include the ability to dissolve in various liquids and the state of aggregation under standard conditions.

At room temperature, a common alkaloid is a crystalline solid. Colors and smells, as a rule, do not have. The taste is mostly bitter, astringent, unpleasant. They exhibit optical activity in solutions.

Some of these substances under standard liquid conditions are oxygen-free alkaloids, about 200 species in total. For example, nicotine, pachycarpine, coniine.

If we talk about solubility in water, then only caffeine, ephedrine, ergometrine can do this completely. The remaining representatives of this class of compounds are soluble only in liquid organic substances (solvents).

Action on the human body

An alkaloid is a substance that has a strong effect on the human and animal body. What is this influence?

1. A huge impact is exerted on the nervous system, the endings of nerve cells, synapses, and neurotransmitter processes. Different groups of alkaloids act on these parts of the body as psychotropic, reflex, antitussive, stimulants, narcotic drugs, analgesics. When used correctly for medical purposes, strictly dosed and accurately, these effects are beneficial. However, the slightest overdose can lead to very serious and sad consequences.
2. Action on the cardiovascular system - antiarrhythmic, improves blood circulation, antispasmodic, hypotensive, choleretic.

If preparations based on alkaloids are used for other purposes or without compliance with the required dosage, the following consequences are possible:

• impaired vision, hearing;
• respiratory failure, heaviness in the chest;
• dizziness, nausea, vomiting;
• bleeding;
• dry mouth;
• a sharp increase or decrease in blood pressure;
• severe poisoning with a fatal outcome.

A significant part of the alkaloids in their physiological effects on humans are poisons, strong, causing convulsions and death (strychnine, morphine, belladonnin). The other part is narcotic compounds that cause addiction. Psychological, emotional and physical (nicotine, caffeine, cocaine). Therefore, with these compounds, you need to be extremely careful and use only on the advice and prescription of a doctor.

Use in medicine

In this area, plants containing alkaloids are the basis for many drugs with a wide spectrum of action, or, conversely, highly specialized ones. On the basis of such raw materials, candles, tinctures, tablets, ampoule solutions are obtained. The action is aimed at the treatment of cardiovascular diseases, respiratory organs, nervous system and endings, mental disorders. Also for the treatment of the digestive system, as contraceptives, for oncological ailments, to eliminate alcohol addiction and many other areas.

Under natural conditions, alkaloids contain medicinal herbs and plants. Today, about 10,000 names of these substances are known, and almost all of them are extracted from just such raw materials.

In parts of fungi, cells of bacteria, algae, echinoderm alkaloids were not found. Alkaloidal compounds have been extracted from the cells of some animals, but there are very few of them.

Thus, it turns out that the main supplier, an inexhaustible source of these substances for medical purposes, human life, and industry are plants containing alkaloids.

medicinal plants

What are these plants? There are, in fact, too many to mention them all. However, you can name the most common and frequently used by man.

Medicinal herbs and plants are a very important field of modern medicine. After all, most of the drugs are synthesized on the basis of natural raw materials. They have been used since antiquity and have not lost their relevance to humans today. On the contrary, over time, people are increasingly striving to discover and study the composition of such plants in order to find something important, something that will help solve the problem of many incurable diseases.

The most common alkaloid

This is considered to be an opium derivative - codeine. It can be isolated by special chemical reactions from morphine. Compared to the latter, it is safer to use, as it is soft in action. However, the effectiveness as an analgesic, sedative drug is not worse than that of morphine or opium itself.

Therefore, codeine-based drugs are very widespread in medicine and are used by people of all countries. The only limitation is the dosage. It should be used only on the recommendation and under the supervision of a physician.

Opium and its alkaloids

Opiates - so in medicine and chemistry it is customary to call all those opium alkaloids that can be isolated from it and synthesized on its basis. What are these connections? Unfortunately, today almost everyone hears about them and does not always have a good reputation and find a worthy, correct application. These are alkaloids such as:

• morphine;
• papaverine;
• heroin;
• codeine.

In medicine, these substances are used as antitussive, analgesic, sedatives. On the basis of codeine, a number of drugs have even been created for colds in children.

However, compounds such as opium and heroin are used not only for medical purposes, but also as heavy intoxicating drugs. They cause a terrible dependence of the human body and over time can cause serious harm to health, even people's lives.

To alkaloids belong to substances of plant origin contained in many plants. Currently, about 10,000 alkaloids are known.

Chemical properties of alkaloids

A common property for most alkaloids is the presence in their molecules of nitrogen contained in the cycles. Thus, alkaloids belong to heterocyclic compounds. Alkaloids are organic bases and form salts with acids. In most cases, alkaloids are found in plants in the form of salts of malic, tartaric, citric and other acids. In the form of salts, they are soluble in water. Free alkaloids can be obtained by treating salts with alkalis. In the free form, alkaloids are generally insoluble in water, but soluble in organic solvents. A property common to all alkaloids is also that they are physiologically extremely active substances that have a strong effect on the animal organism; many of them are poisons.

The effect of alkaloids on the human body

Most alkaloids act on the nervous system: in small doses they have an exciting effect, and in large doses they are depressing. For example, cocaine, widely used in medicine as a local anesthetic, acts on the sensitive endings of the peripheral nervous system. Curare - an alkaloid contained in the juice of some South American plants, acts on the motor endings of the nervous system and therefore causes paralysis; that is why it was used by the Indians for wetting arrows. The morphine contained in the milky juice of the poppy acts on the central nervous system, causing sleep; it is used medicinally as a general anesthetic. The nicotine contained in tobacco also acts on the central and peripheral nervous system. The berries of belladonna and dope contain atropine, which has a strong effect on the motor nerves of the eye, dilating the pupil.

The structure of alkaloids

The structure of alkaloids is very diverse. Depending on the chemical nature of the nitrogenous heterocycle included in their composition, they are divided into the following major groups: 1) pyridine derivatives; 2) pyrrolidine derivatives; 3) quinoline and isoquinoline derivatives; 4) indole derivatives; 5) purine derivatives, which include alkaloids - caffeine and theobromine; 6) alkaloids of terpenoid nature.

In some alkaloids, we are dealing with a combination of various nitrogenous heterocycles in a molecule. So, for example, in the nicotine molecule, pyridine and pyrrolidine are interconnected. Usually, however, nicotine is included in the group of pyridine alkaloids. Tobacco contains a number of alkaloids, of which the main ones are nicotine, ornicotine and anabazine.

Alkaloid nicotine

Nicotine when oxidized, it forms nicotinic acid, which is an anti-pellagric vitamin; in the form of amide is an integral part of some dehydrogenases. Free nicotine is a colorless, oily liquid. It is a highly toxic substance that acts on the central and peripheral nervous systems. With nicotine poisoning, death occurs from respiratory paralysis. Nicotine is obtained in large quantities from the waste products of the tobacco industry and is used to control insects that harm agriculture.

Nornicotine- an alkaloid obtained by removing the methyl group from nicotine. Anabazine was discovered by the largest Soviet researcher in the field of alkaloid chemistry, Academician A.P. Orekhov in the Central Asian plant Anabasis aphylla. Just like nicotine, anabazine is used to control insect pests in agriculture. Research by A.A. Shmuk, the greatest authority in the field of tobacco chemistry, showed that individual botanical types of tobacco can vary greatly in terms of the content of nicotine, nornicotine and anabasine. For example, cigarette tobacco (Nicotiana tabacum) and shag (Nicotiana rustica) contain nicotine. A number of species contain only traces of nicotine and predominantly nornicotine. Tobacco belonging to the species Nicotiana glauca contains only anabasine.

Quinine alkaloid

The most important representative of the group of alkaloids belonging to quinoline derivatives is quinine, found in cinchona bark. It is used in medicine as a very effective medicine in the treatment of malaria.

Alkaloid morphine

Morphine- a representative of the group of isoquinoline alkaloids, found in opium - condensed milky juice of the opium poppy. Opium contains a large number of different alkaloids and is widely used in medicine as a sedative, and in large doses as a drug. Morphine is widely used as a pain reliever.

Ergot alkaloids

The group of alkaloids - indole derivatives, includes a number of alkaloids contained in ergot horns. Ergot is a wintering form of the fungus. Claviceps purpurea developing in rye grain. Ergot is very poisonous, and getting ground horns into flour can lead to mass poisoning. Therefore, the cleaning of infected grain from ergot horns is the most important operation in the processing of such grain. Ergot horns are used in medicine. At present, the cultivation of ergot on synthetic media is widely used to obtain ergot alkaloids for their use in medicine. By changing the composition of the medium, the yield of alkaloids can be significantly increased. The structure of ergot alkaloids is based on lysergic acid or its isomer - isolizergic acid, which are indole derivatives synthesized in ergot mycelium from tryptophan and mevalonic acid. Combining with one or more amino acids, pyruvic acid or amino alcohols, lysergic acid forms one or another ergot alkaloid. 12 alkaloids have been isolated from ergot horns: ergotamine and ergotamine, ergosine and ergosinine, ergocristine and ergocristinine, ergocryptine and ergocryptinine, ergocornine and ergocorninine, ergobasine and ergobasinine. Ergot alkaloids are a good example of the fact that this plant usually contains a whole complex of alkaloids; related in their chemical nature. We observe the same picture in tobacco, opium poppy, cinchona.

ALKALOIDS(from Arabic alcali - alkali and Greek. eidos - kind, similar) - a large group of natural nitrogen-containing compounds of a basic nature. They often have strong pharmacological effects. At present, more than 5,000 alkaloids have been isolated from plants, sometimes twice the figure is indicated; for 3000 a building is established. The most widely distributed alkaloids among angiosperms. The seeds of poppy, solanaceous, legumes, kutra, madder, buttercup, loganiaceae, etc. are especially rich in them. In algae, mushrooms, mosses, ferns and gymnosperms, they are relatively rare. The name alkaloids was proposed by Meissner in 1819. In plants, alkaloids are found in the form of salts of organic and inorganic acids in actively growing tissues, epidermal and hypodermal cells, in the lining of vascular bundles and latex passages. They are dissolved in cell sap, accumulate in leaves, fruits, seeds, bark, underground organs. Various parts plants may contain different alkaloids. Usually the concentration of alkaloids in the plant is small and amounts to hundredths and tenths of a%. With a content of 1 - 3%, the plant is considered rich in alkaloids (highly alkaloid-bearing). Only a few plants, such as cultivated forms of cinchona, contain up to 15 - 20% alkaloids. The plant, as a rule, includes not one, but several alkaloids (kataranthus pink - more than 60 alkaloids).

The biological functions of alkaloids have not yet been finally elucidated, but recently more and more preference has been given to their active role in metabolism; they are considered a kind of stimulants and regulators of biochemical processes.

There is evidence of the participation of alkaloids in redox processes. The protective role of alkaloids is undoubted.

Most oxygen-containing alkaloids are odorless, bitter-tasting, colorless crystalline solids, only a few are colored (for example, sanguinarine is orange). Oxygen-free alkaloids are volatile liquids with an unpleasant odor (coniine, pachycarpine, nicotine). Alkaloids are optically active.

Alkaloids are bases, practically insoluble in water (with the exception of caffeine, ephedrine, ergometrine) and highly soluble in non-polar organic solvents. Some salts of alkaloids (for example, papaverine hydrochloride) are soluble in chloroform.

The wide variety of alkaloids makes it difficult to classify them. A.P. Orekhov divided them into groups, based on the structure of nitrogen-containing heterocycles. This classification has been refined and developed by other scientists and is widely used in chemistry and pharmacognosy. The following main groups of alkaloids are distinguished:

1) pyrrolidine group (I);

2) piperidine group (II);

3) pyridine (III) group;

4) pyrrolizidine group (IV);

5) quinolizidine group (V);

6) quinoline group (VI);

7) isoquinoline group (VII);

8) quinazoline group (VIII);

9) indole group (IX);

10) a group of dihydroindole or betalains;

11) imidazole group (X);

12) acridine group (XI);

13) purine group (XII);

14) a group of steroidal alkaloids;

15) a group of terpene alkaloids;

16) a group of alkaloids without heterocycles.

The classification of alkaloids according to the structure of the main heterocycle has a number of advantages, but does not reflect biogenetic relationships among alkaloids.

When working on the introduction of labeled precursors into alkaloids, it was found that most of these are amino acids. This gave rise to

R. Hegnauer to divide all alkaloids into three groups: true alkaloids, protoalkaloids And pseudoalkaloids. True alkaloids include N-heterocyclic compounds formed from biogenic amines, which in turn arose by decarboxylation of proteinogenic amino acids.

Protoalkaloids do not have N-heterocycles and, as a rule, are plant amines, for example, ephedrine, spherophysin, etc. Pseudoalkaloids include a skeleton, which is based not on amino acids, but on other compounds. These include steroidal and terpene alkaloids.

In connection with modern ideas about the ways of biosynthesis of alkaloids, a number of authors propose to classify true alkaloids based on the amino acids that are their precursors. In Russia, for the classification of medicinal plant materials containing alkaloids, the classification developed by A.P. Orekhov was used.

To detect alkaloids in plant materials, general alkaloid (sedimentary) reactions and chromatography are used. Reactions are carried out with 1 - 5% acid extracts from raw materials. For the quantitative determination of alkaloids, instrumental physicochemical, gravimetric and volumetric methods are used.

Currently, more than 80 alkaloids have been used in medical practice. They are used in their pure form, as part of galenic and novogalenic preparations obtained from alkaloid raw materials, are part of many others. complex preparations. The use of alkaloids is associated with the production of tonic drinks (tea, coffee, cocoa), as well as the tobacco industry. A number of alkaloids are used in agriculture as insecticides. On the basis of known alkaloids, new substances with the necessary pharmacological properties are synthesized.

Alkaloids have a number of negative properties. With the use of some alkaloids develops predilection, drug dependence (drug addiction). Many alkaloids are strong poisons that can cause fatal poisoning.

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Currently, about 10,000 alkaloids have been discovered, of which about 4,000 have a proven structure. Such a huge number and variety of alkaloids does not make it possible to develop a unified classification.

The classification of alkaloids can be based on different principles, therefore, several types of classifications of alkaloids are distinguished.

1. At the core pharmacological classification lies the nature of the pharmacological action of alkaloids on the body:

• narcotic alkaloids;
• local anesthetic alkaloids;
• antispasmodic alkaloids, etc.

2. At the core botanical classification lies the systematic belonging of the plants from which the alkaloids are isolated to a particular genus or family:

• tobacco alkaloids;
• poppy alkaloids;
• ergot alkaloids, etc.

3. At the core biogenetic classification, proposed by the English scientist Hegnauer, lies the structure of amino acids, which are the likely precursors of alkaloids in plants:

• tryptophan alkaloids;
• phenylalanine alkaloids, etc.

4. Most convenient and most often used in pharmacognosy chemical classification proposed by A.P. Orekhov, which is based on the features of the chemical structure of alkaloids, in particular, the structure of a nitrogen-containing heterocycle.

Classification according to the structure of the carbon-nitrogen cycle

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Depending on the structure of the carbon-nitrogen cycle A.P. Orekhov divided all alkaloids into 13 groups:

1. Alkaloids with nitrogen in the side chain or acyclic alkaloids (without heterocycles): ephedrine from ephedra species, capsaicin from capsicum fruits, colchicine and colchamine from corms of Colchicum species.2. Alkaloids, derivatives of pyrrolidine and pyrrolizidine: platyfillin from flat-leaved ragwort.

3. Alkaloids, derivatives of pyridine and piperidine, are divided into several groups.

a) simple derivatives of pyridine and piperidine: lobelin from swollen lobelia, coniine from the fruits of spotted hemlock;

b) bicyclic non-condensed systems: anabasine from leafless anabasis, nicotine from tobacco leaves;

c) bicyclic condensed systems of piperidine and pyrrolidine (tropane derivatives): hyoscyamine, scopolamine from belladonna, henbane, dope species

4. Alkaloids, derivatives of quinolizidine: pachycarpine, thermopsin, cytisine (Sophora thick-fruited, types of thermopsis).

5. Alkaloids, quinoline derivatives: quinine from cinchona bark, echinopsin from mordovnik fruits.

6. Alkaloids, derivatives of isoquinoline: morphine, codeine and papaverine from poppy pods, chelerythrin, sanguinarine from celandine and machlea grass, glaucine from yellow machka grass, berberine from barberry roots.

7. Alkaloids, indole derivatives: ergot alkaloids, periwinkle alkaloids, reserpine and aymaline from rauwolfia roots, strychnine from chilibukha seeds, vinblastine and vincristine from rose cataranthus leaves.

8. Purine alkaloids: caffeine from tea leaves, coffee seeds, theobromine from chocolate tree seeds.

9. Alkaloids, derivatives of quinazoline: peganine from the common harmala herb.

10. Alkaloids, derivatives of imidazole: pilocarpine from the leaves of pilocarpus species.

11. Steroid alkaloids: solasonine from the herb nightshade lobed, hellebore alkaloids.

12. Diterpene alkaloids: alkaloids of aconites and larkspurs.

13. Alkaloids of unknown structure.

Based on this classification, raw materials containing alkaloids are also systematized.