The effect of tannins on the human body. Tannin in tea and wine

Foaming agents (surfactants) - surfactants Used as cleaning and disinfecting agents. Necessary to ensure even distribution of the paste in hard-to-reach places of the oral cavity, as well as for additional removal of plaque

Aromatic substances Used to improve the palatability of toothpaste, determine a pleasant aroma. The most common flavors are mint, cinnamon, eucalyptus, which have a refreshing effect. All toothpastes on our market are divided into:

Tannins This group of plant polyphenols has an astringent taste and the ability to "tan" raw hides into leather. In air, they oxidize, forming flobafen - brown-colored substances, and lose their tannic properties. Tanning

Nutrients Before we talk about the food that a child can eat, it is necessary to discuss the most important chemicals that make it up and how they are used by the body. A child's body can be compared to a building under construction. Required

Tannins (tanides) are plant high-molecular phenolic compounds that can precipitate proteins and have an astringent taste.

The term "tannins" has developed historically, thanks to the ability of these compounds to turn raw animal skin into durable skin, resistant to moisture and microorganisms. The use of this term was officially proposed in 1796 by Seguin to designate substances in the extracts of certain plants that can carry out the tanning process.

Tanning is a complex chemical interaction of tannins with collagen molecules, the main protein of connective tissue. Tanning properties are possessed by polynuclear phenols containing more than one hydroxyl in the molecule. With a flat arrangement of tanide on a protein molecule, stable hydrogen bonds arise between them:

Fragment of a protein molecule Fragment of a tanide molecule

The strength of the interaction of tanide with protein depends on the number of hydrogen bonds and is limited by the size of the molecule of the polyphenolic compound. The molecular weight of tannins can be up to 20,000. At the same time, there are 1-2 phenolic hydroxy groups per 100 molecular weight units in tannins. Therefore, the number of hydrogen bonds formed is numerous and the tanning process is irreversible. Hydrophobic radicals oriented to the external environment make the skin inaccessible to moisture and microorganisms.

Not all tannins are capable of true tanning. This property distinguishes compounds having a molecular weight of 1,000 or more. Polyphenolic compounds with a mass of less than 1,000 are not capable of tanning leather and have only an astringent effect.

Tannins are very widely used in industry. Suffice it to say that the world production of tannins exceeds 1,500,000 tons per year, and the share of vegetable tannins is up to 50-60% of the total.

Distribution in the plant world and the role of tannins in plants. Tannins are widely found in representatives of angiosperms and gymnosperms, algae, fungi, lichens, in club mosses and ferns. They are found in many higher plants, especially dicots. Their greatest number was found in a number of representatives of the families Fabaceae, Myrtaceae, Rosaceae, Anacardiaceae, Fagaceae, Polygonaceae.

Tannins in the plant are located in cell vacuoles and are adsorbed on cell walls during cell aging. They accumulate in large quantities in underground organs, bark, but can be found in leaves and fruits.

Tannins perform mainly protective functions in plants. With mechanical damage to tissues, an increased formation of tannins begins, accompanied by their oxidative condensation in the surface layers, thereby protecting the plant from further damage and the negative influence of pathogens. Due to the large amount of phenolic hydroxyls, tannins have pronounced bacteriostatic and fungicidal properties, thereby protecting plant organisms from various diseases.

Classification of tannins. In 1894, G. Procter, studying the end products of the pyrolysis of tannins, discovered 2 groups of compounds - pyrogallic (pyrogallol is formed) and pyrocatechin (pyrocatechin is formed during decomposition):

K. Freudenberg in 1933 specified the classification of G. Procter. He, like Procter, classified tannins according to the end products of their decomposition, but not under pyrolysis conditions, but under acid hydrolysis. Depending on the ability to hydrolyze, K. Freudenberg proposed to distinguish two groups of tannins: hydrolysable and condensed. Currently, the classification of K. Freudenberg is more often used.

To the group hydrolysable tannins include compounds built according to the type of esters and decomposing during acid hydrolysis into constituent components. The central link is most often glucose, less often other sugars or alicyclic compounds (for example, quinic acid). The alcohol hydroxyls of the central residue can be ether bonded to gallic acid, forming a group gallotannins, or ellagic acid, forming a group ellagitannins.

Gallotannins- esters of gallic acid, the most common in the group of hydrolysable tannins. There are mono-, di-, tri-, tetra-, penta- and polygalloy ethers. The representative of monogalloyl ethers is b-D-glucogallin:

An example of polygalloyl ethers is Chinese tannin, the structure of which was first established in 1963 by Haworth:

ellagitannins are esters of sugar and ellagic acid or its derivatives. Ellagic acid is formed by the oxidation of two molecules of gallic acid to hexaoxydiphenic acid, which immediately forms a lactone - ellagic acid:

As in the previous case, the sugar component of ellagitannins is most often glucose.

Non-sugar esters of gallic acids are esters of gallic acid and a non-sugar component, such as quinic acid, hydroxycinnamic, etc. An example of this group of substances is 3,4,5-trigalloylquinic acid.

condensed tannins differ from hydrolysable ones in that during acid hydrolysis they are not split into constituent components, but on the contrary, under the action of mineral acids, dense red-brown polymerization products, flobaphenes, are formed.

Condensed tannins are formed mainly by catechins and leucocyanidins, and, much less frequently, by other reduced forms of flavonoids. Condensed tannins do not belong to the "Glycosides" group: there is no sugar component in condensed tannins.

The formation of condensed tannins can occur in two ways. K. Freudenberg (30s of the XX century) established that the formation of condensed tannins is a non-enzymatic process of autocondensation of catechins or leukocyanidins (or their cross-condensation) as a result of exposure to atmospheric oxygen, heat and acidic environment. Autocondensation is accompanied by rupture of the pyran ring of catechins and the C-2 carbon atom of one molecule is connected by a carbon-carbon bond to the C-6 or C-8 carbon atom of another molecule. In this case, a sufficiently extended chain can be formed:

According to another scientist, D. Hatway, condensed tannins can be formed as a result of enzymatic oxidative condensation of molecules according to the “head to tail” type (ring A to ring B) or “tail to tail” (ring B to ring B):

In plants containing condensed tannins, there are necessarily their precursors - free catechins or leukocyanidins. Often there are mixed condensed polymers consisting of catechins and leucocyanidins.

As a rule, tannins of both condensed and hydrolysable groups are simultaneously present in plants.

Physical and chemical properties of tannins. Tannins are characterized by high molecular weight - up to 20,000. Natural tannins, with a few exceptions, are known to date only in an amorphous state. The reason for this is that these substances are mixtures of compounds that are similar in chemical structure but differ in molecular weight.

Tannins are yellow or brown compounds that form colloidal solutions in water. Soluble in ethanol, acetone, butanol and insoluble in solvents with pronounced hydrophobicity - chloroform, benzene, etc.

Gallotannins are poorly soluble in cold water and relatively well in hot water.

Tannins have optical activity and are easily oxidized in air.

Due to the presence of phenolic hydroxyls, they are precipitated by salts of heavy metals and form colored compounds with Fe +3.

Isolation of tannins from vegetable raw materials. Since tannins are a mixture of various polyphenols, their isolation and analysis presents a certain difficulty.

Often, to obtain the amount of tannins, raw materials are extracted with hot water (tannins are poorly soluble in cold water) and the cooled extract is treated with an organic solvent (chloroform, benzene, etc.) to remove lipophilic substances. Then the tannins are precipitated with salts of heavy metals, followed by the destruction of the complex with sulfuric acid or sulfides.

To obtain a fraction of tannins similar in chemical structure, it is possible to use the extraction of raw materials with diethyl ether, methyl or ethyl alcohol with preliminary removal of lipophilic components using solvents with pronounced hydrophobicity - petroleum ether, benzene, chloroform.

The isolation of some components of tannins by precipitation from aqueous or water-alcohol solutions with lead salts is widespread. The resulting precipitates are then treated with dilute sulfuric acid.

When isolating the individual components of tannins, chromatographic methods are used: adsorption chromatography on cellulose, polyamide; ion exchange on various cation exchangers; distribution on silica gel; gel filtration on molecular sieves.

Identification of individual components of tannins is carried out using chromatography on paper or in a thin layer of sorbent, using spectral analysis, qualitative reactions and the study of cleavage products.

Qualitative analysis of tannins. Qualitative reactions to tannins can be divided into two groups: precipitation reactions and color reactions. To carry out qualitative reactions, raw materials are most often extracted with hot water.

Precipitation reactions. 1. When tannins interact with a 1% gelatin solution prepared in a 10% sodium chloride solution, a precipitate forms or the solution becomes cloudy. When excess gelatin is added, the turbidity disappears.

2. Tanides give abundant precipitation with alkaloids (caffeine, pachycarpine), as well as some nitrogenous bases (urotropine, novocaine, dibazol).

3. When interacting with a 10% solution of lead acetate, tannins of the hydrolysable group form a flocculent precipitate.

4. Tannins of the condensed group form a flocculent precipitate in reaction with bromine water.

color reactions. The tannins of the hydrolyzable group with a solution of iron ammonium alum form black-blue colored compounds, and the condensed group - black-green.

If the plant simultaneously contains tannins and hydrolysable and condensed groups, then first hydrolysable tannins are precipitated with a 10% solution of lead acetate, the precipitate is filtered off, and then the filtrate is reacted with a solution of iron ammonium alum. The appearance of a dark green color indicates the presence of substances of the condensed group.

Quantitative determination of tannins. While there are about 100 different methods for the quantitative determination of tannins, an accurate quantitative analysis of this group of biologically active substances is difficult.

Among the widely used methods for the quantitative determination of tannins, the following can be distinguished.

1. Gravimetric - based on the quantitative precipitation of tannins by gelatin, salts of heavy metals, etc.

2. Titrimetric - based on oxidative reactions, primarily with potassium permanganate.

3. Photoelectrocolorimetric - based on the ability of tannins to form stable colored reaction products with iron oxide salts, phosphotungstic acid, etc.

The State Pharmacopoeia of X and XI editions recommends a titrimetric method for the quantitative determination of tannins.

Tannins are, of course, not derived from the mighty oak tree. They owe their name to high-molecular phenolic natural compounds, which are endowed with astringent and tanning properties, and are quite widespread in the plant world. They are found in wood, bark, leaves, roots and fruits of plants. Phenolic compounds, from the point of view of biology, are plant secretions - urea. Over time, accumulating in certain areas, they form growths.

What are the properties of tannins? You can say big. Phenolic compounds affect the organic environment and eliminate the influence of microorganisms. Tannins of plants are characterized by a special astringent taste and are divided into organic and mineral. Organic are of plant and animal origin.

When did humanity come to understand the importance of tannins?

It can be safely asserted, even at the dawn of the birth of this very humanity. The cold at all times was “not an aunt” and it was a vital necessity to dress the freezing tribes in the skins of dead animals. This saved from the cold, and was the first clothing of a person, not counting, of course, Adam's fig leaf. But the tribesmen faced one important problem - the skins of those very killed animals exuded a terrible smell and, moreover, became unsuitable for wearing because of their rigidity.

As time went on, people gained little experience in cutting leather, began to scrape everything unnecessary from the surface and dry them. But, anyway, brittleness after drying was present, and then people began to rub the skins with fat, and to give them elasticity - to crush. But these attempts were not crowned with success.

Through creative experiments, that is, by trial and error, it was possible to find out that some parts of plants are endowed with amazing properties, they make the processed skin soft, strong and durable. These same substances that can turn the skin into a material for further use, and began to actually be called tannins. But, it is quite possible that oak served as the basis for their name, since oak cara was most often used for these purposes, as a source of tannin.

Properties of vegetable tannins

As a rule, tannins isolated from plants are amorphous and do not have a pronounced crystalline structure. Characterized by a distinct acidic nature and the ability to tan the skin. This was the most useful quality of tannins.

Subsequent experiments revealed the special properties of tannins. They have bactericidal, astringent, anti-inflammatory and hemostatic properties. Their widespread use was not long in coming, they began to be used both externally and internally. A very interesting fact came to light, tannins, it turns out, are also found in vegetables, fruits, berries, and many herbs.

The benefits of tannins

In the form of a rinse, tannins are used in the treatment of stomatitis, tonsillitis, pharyngitis, in the form of compresses - for cuts, abrasions, etc.

Food products with these substances have a beneficial effect in preventing the deposition of salts of heavy metals, with diarrhea, and radioactive damage.

They show themselves wonderfully as an antidote.

Tonic tea is used for diseases of the nose, throat, eye diseases, as drops.

Cognac also contains tannins, which improves the perception of vitamin C.

Tannins (tannins) are part of natural coffee and determine its bitter taste. By the way, tannin finds its application in the production of ink, medicine, dyeing, to obtain pyrogallol and gallic acid. Tannins give elasticity to blood vessels.

I would like to note the bay leaf, which most housewives find use in cooking. It also contains tannins. Bay leaf infusion is favorable for problems of the gastrointestinal tract, bleeding, menstrual cycles and menopause. Recommend infusion and physicians as a method of eliminating kidney stones.

Quince lovers do not even realize that it contains substances such as epicatechin and catechin, which cleanse the intestines of putrefactive deposits and toxins, bind carcinogenic compounds in the body, and counteract the development of metastases and diverticulitis.

Separately, I would like to say about medicinal herbs, in which there are a lot of tannins.

Harm of tannins

1. Excessive use of tannins provokes, do not forget about it.
2. It is best to consume foods that are rich in tannins - on an empty stomach or in the intervals between meals. Otherwise, they interact with food proteins, completely without reaching the mucous membrane of the stomach and intestines.

Animals), or else constitute (pathological tannins) a more or less significant part of the painful outgrowths that form on the leaves and other organs of some species of oak and sumac due to a prick produced by insects (see tannins).

Properties

Tannins are basically amorphous, have a more or less pronounced acidic character and have the property (mainly physiological tannins) to tan the skin (skins), that is, to take away their ability to rot and harden when dried.

Being easily oxidized substances, they turn brown in the presence of alkalis, absorbing atmospheric oxygen, and in many cases act reductively, for example, on salts of noble metals, and some on Fehling's liquid.

History of study

Despite the fact that tannins have been known for a long time (tannin was first obtained by Nicolas Deyet and independently by Seguin in 1797 and was already in the hands of Berzelius in 1815 in a fairly pure state) and studied a lot, by the beginning of the 20th century they were insufficiently studied, and not only the chemical nature and structure of almost all of them remained unclear, but even the empirical composition of very many of them was made differently by different researchers. This is easily explained, on the one hand, by the fact that, being mostly substances that are not capable of crystallization, they are difficult to obtain in pure form, and on the other hand, by their low stability and easy changeability. G. Glazivets (1867), like many others, considered all tannins to be glycosides or bodies similar to them; however, later studies have shown that tannin, although, apparently, is found in combination with glucose in algarobillas and myrobolans (Zöllfel, 1891), but in itself is not a glycoside (H. Schiff 1873), also tannic acids of oak bark ( Etti 1880, 83, 89, Löwe 1881), as well as many other tannins, have nothing to do with glycosides, and the preparation of sugary substances from some of them was due solely to the impurity of the studied preparations. At present, it is possible to judge with sufficient certainty only about the structure of tannin, which is anhydride of gallic acid (see and below); as for others, it is only, apparently, possible to assume in them, judging by the decomposition reactions and some others, partly anhydride compounds of polyhydric phenolic acids and phenols, formed either as simple or as esters, partly aromatic ketone acids, which are condensation products of derivatives of gallic acid; but part of the tannins must still be considered glucosides. In view of the unknown structure, the impossibility of a natural grouping of tannins is self-evident - in fact, tannins are distinguished into a special group of organic compounds that have a certain set of common features, only thanks to the unknownness of their structure. It is very possible that, after the latter is clarified, they will be distributed over time among various classes of organic compounds, and then there will no longer be a need for a special common name for them, and the current name "tannin", according to the recent proposal of F. Reinitzer (English) Russian, will probably have to be kept only for those of them that are actually capable of tanning skins. Their division according to the coloration produced with iron oxide salts into iron-blue (Eisenblauende) and iron-green (Eisengrünende) is now abandoned, because the same tannin can sometimes give a blue, and sometimes a green color, depending on which iron salt is taken. , and moreover, the coloring can change from an increase, for example, a small amount of alkali. The division of tannins into physiological(see above), tanning the skin and at the same time giving catechol when dry distilled and not giving gallic acid when boiled with weak sulfuric acid, and pathological, less suitable for tanning (although precipitating with a solution of glue), when dry distilled, they give pyrogallol, and when boiled with weak sulfuric acid - gallic acid, also does not fully correspond to the facts, because, as is now known, even pathological tannins can, although not so successful, serve for tanning, and in addition, tannin, for example, being predominantly a pathological tannin, apparently also occurs as a normal product (sumac, algarobilla, myrobolans). As acids, tannins form metal derivatives - salts, of which lead, which are water-insoluble amorphous precipitates, are often used to extract tannin from aqueous extracts of tannins, as well as in analysis.

How to get

To obtain tannin in a pure state, natural tannins are extracted with water or other solvents: strong or weak alcohol, pure ether or mixed with alcohol, acetic ether, etc.; the extracts are evaporated, and the tannins obtained in the residue are purified by treating them with one or another of the indicated solvents. More often, having prepared an aqueous or aqueous-alcoholic extract, the tannin is extracted from it by shaking with acetic or ether or with a mixture of them, or it is precipitated (preferably fractionated) with acetic lead and, after filtering, the precipitates of lead compounds are decomposed with hydrogen sulfide. Apparently, the latter method, practiced very often by former researchers, does not always give satisfactory results in terms of the purity of the products obtained (Etti). They sometimes use quinine acetate, copper acetate, emetic stone, common salt, hydrochloric acid, etc. to precipitate tannins from aqueous extracts. Dialysis is sometimes used for purification, which gives good results with tannin (Löwe, Biedel).

Description of individual tannins

When describing tannins, it is necessary to dwell in detail on only a few most important for practice and better studied.

Tannin

Tannin, gallotannic acid or simply tannic acid (Galläpfelgerbsäure, Gallusgerbsäure, acide gallotannique), is found in various varieties of ink nuts, pathological knoppers, sumac, algarobilla, myrobolans; has the composition C 14 H 10 O 9 ; represents astringent taste amorphous powder, soluble in water, alcohol and acetic ether, insoluble in ether, benzene, etc.; optically inactive; gives a black-blue precipitate with ferric chloride in an aqueous solution, which is used as a qualitative reaction to iron oxide salts; easily oxidized, absorbing oxygen from the air in the presence of alkalis and reducing copper oxide from salts of its oxide and silver salt; precipitated from aqueous solutions (unlike gallic acid) by glue, raw skin, alkaloids, albuminates, weak hydrochloric and sulfuric acids, and many salts (eg, common salt). According to K. Bottinger (1888), the combination of tannin with glue contains about 34% tannin. Tannin decomposes carbonic salts, revealing clearly acidic properties. Its salts are amorphous, mostly insoluble, and their composition indicates the presence of only one carboxyl in its particle (H. Schiff). When heated to 210 °, tannin gives pyrogallol; when boiled with weak sulfuric acid or caustic potash, it turns completely into gallic acid. Different grades of commercial tannin also yield variable amounts of glucose, which led Strecker et al. to consider tannin as a gallic acid glucoside. However, completely pure tannin, obtained, for example, by extraction with acetic ether, does not form traces of glucose (Löwe). It is possible that glucoside, but not gallic acid, but tannin (H. Schiff) is present in commercial varieties as an admixture. acid gives the amide of this acid and its ammonium salt; when boiled with acetic anhydride, it forms pentaacetyl ester C 14 H 5 (C 2 H 3 O) 5O 9 . These reactions determine the structure of tannin as digallic acid, which is gallic anhydride

C 6 H 2 (OH) 3 CO-O-C 6H 2 (OH) 2 SONO.

In confirmation of this structure of tannin, G. Schiff (1873) obtained from gallic acid by heating it with phosphorus oxychloride, as well as by evaporating its aqueous solution with arsenic acid, digallic acid according to the equation

2C 6 H 2 (OH) 3COHO - H 2 O \u003d C 6H 2 (OH) 3 CO-O-C 6H 2 (OH) 2 SONO

in its properties, reactions and derivatives, it is identical with tannin.

tannin is widely used in medicine, in the production of ink, dyeing, for the production of gallic acid and pyrogallol, but is not used for tanning leather). In addition to digallic acid, Schiff artificially obtained anhydrides and other polyhydric phenolic acids, as well as sulfophenolic acids, with the properties of tannins and close to tannin. These include: dinitrogallo- and diphloroglucincarboxylic acids obtained (1888) by the action of phosphorus oxychloride on the corresponding isomers of gallic acid and having the composition C 14 H 10 O 9 .

Catechudonic acids

They are found together with catechins of a similar composition in various varieties of catechus and in gambir (see also Tanning materials). They are catechin anhydrides, from which they can also be obtained artificially by simply heating up to 130-170 °, boiling with soda or heating with water at 110 °. The composition of catechins dried at a temperature of about 100° (they contain up to 5 shares of water of crystallization, which they lose at this temperature), is expressed by the formulas C 21 H 20 O 9 (\displaystyle C_(21)H_(20)O_(9))(Liebermann u Teuchert 1880), C 19 H 18 O 8 (\displaystyle C_(19)H_(18)O_(8)), (Etti, Hlasiwetz) and others. Catechins crystallize in the form of very small needles of a light yellow color, give a green color, but do not precipitate with glue, when melted with KNO, they decompose into phloroglucinol and protocatechuic acid, and upon dry distillation they form pyrocatechol. For catechin C 21 H 21 O 9 (\displaystyle C_(21)H_(21)O_(9)) diacetyl and dibenzoyl ethers were obtained (Lieb. u. Teuch.). catechin C 18 H 18 O 8 (\displaystyle C_(18)H_(18)O_(8)) at 140° with diluted sulfuric acid, it decomposes into phloroglucinol and pyrocatechol. WITH F e C l 3 (\displaystyle FeCl_(3)) it reacts like pyrocatechol, and with pine wood - like phloroglucinol, representing, as it were, a molecular compound of these two phenols 2 C 6 H 3 (O H) 3 − C 6 H 4 (O H) 2 (\displaystyle 2C6H_(3)(OH)_(3)-C_(6)H_(4)(OH)_(2))(Etty). Katehu-D. acids, according to Etty (1877-81), have the composition C 38 H 34 O 15 (\displaystyle C_(38)H_(34)O_(15)), C 38 H 32 O 14 (\displaystyle C_(38)H_(32)O_(14)) And C 36 H 34 O 15 (\displaystyle C_(36)H_(34)O_(15)) and represent reddish-brown amorphous powders with the characteristic properties of tannins. By heating catechins to a higher temperature or with mineral acids, anhydrides are obtained, formed with an even greater loss of water (Etti).

Maclurin

Maclurin, or morinotannic acid, C 13 H 10 O 6 + H 2 O (\displaystyle C_(13)H_(10)O_(6)+H_(2)O)(Hiasiwetz 1863, Benedict 1877) and morin C 15 H 10 O 7 + 2 H 2 O (\displaystyle C_(15)H_(10)O_(7)+2H_(2)O)(Löwe 1875, Benedict u. Hazura 1884) are found in the yellow tree (Morus tinctoria or Maclura aurantiaca, used in dyeing), from which they are extracted by boiling with water and separated, taking advantage of the lower solubility of morine in water. Maclurin, a light yellow crystalline powder, from the properties that characterize tannins, has only the ability to give a black-green precipitate with iron (a mixture of nitrous oxide and oxide) and precipitate with glue, alkaloids and albuminates, but is not applicable for tanning. Like many tannins, it breaks down into phloroglucinol and protocatechuic acid according to the equation:

C 13 H 10 O 6 + H 2 O = C 6 H 3 (O H) 3 + C 7 H 3 (O H) 2 C O H O (\displaystyle C_(13)H_(10)O_(6)+H_(2)O =C_(6)H_(3)(OH)_(3)+C_(7)H_(3)\left(OH\right)_(2)COHO).

Such a decomposition occurs quantitatively when it is boiled with a strong solution of caustic potash or at 120 ° C with weak sulfuric acid and indicates the ethereal nature of this substance. Morine, which is the coloring principle of the yellow tree and crystallizes from an aqueous solution in the form of long shiny needles, with the exception of green staining with ferric chloride, does not represent typical properties of tannins. When melted with caustic potash as the main decomposition products, it gives resorcinol and phloroglucinol, when reduced with sodium amalgam, it forms phloroglucinol, and first it turns into isomorin (purple-red prisms), which easily turns back into morin. Both morine and maclurine form partly crystalline, partly amorphous salts with metals, the composition of which, by and large, cannot be considered established.

Tannins are high molecular weight compounds derived from polyhydric phenols. The components have the ability to precipitate proteins and alkaloids, and are endowed with an astringent effect.

Tannins are called so because of their properties. They are able to "tan" the skin, making it waterproof. Previously, the process was used for this, in connection with this, it began to be called "tanning", and the substances themselves - tannins. The components are low toxic.

It should be noted that tannin (tannic acid) was first obtained in 1797. In its pure form, it was produced in 1815.

Tannins are widely used as astringents, bactericidal agents for diseases of the digestive system. In addition, components are used for inflammatory diseases (as rinses), ulcers and other lesions.

Anti-inflammatory activity of tannins with their ability to interact with proteins. As a result, a protective film is formed on the mucous membranes, preventing the further spread of inflammation. Tannins are effective when applied topically as hemostatic agents.

Tannins are present in large quantities in tea. Some components, as mentioned above, have hemostatic, bactericidal and anti-inflammatory properties. (Sleeping tea leaves, for example, are often used for eye diseases). Separate polyphenols (catechins) have the properties of P-vitamin. They help to improve digestion, strengthen the walls of blood vessels of various sizes, reducing their permeability. It is worth noting that black has a complete set of catechins, while these polyphenols are much less.

Tannins actively interact with the acidic environment and iron. So, for example, when brewing tea in an iron container, a brown and cloudy brew is obtained. The acidic environment brightens the tea (this effect can be seen by adding lemon to it). The more tannins in the tea, the more tart and astringent it will taste. You can soften its taste by adding milk.

Best of all, tannins dissolve in hot water (which is why tea is brewed in boiling water). Cooled tea leaves often become cloudy - this is one of the properties of polyphenols. If this does not happen, then this indicates an insufficient amount of tannins in the raw material. Turbid tea leaves can be heated - then it will become transparent again.

In medicine, the properties of tannins are actively used. Tea polyphenols, for example, are known to be powerful antioxidants. In this regard, they are often used for poisoning. This is due to their properties to form safe compounds with various harmful proteins, acids, alkaloids, metals and then remove them from the body.

In nature, many plants contain tannins. Most of these compounds are found in dicots. Algae, mushrooms, ferns, mosses are rich in tannins. There are tannins in pine, willow, beech.

Tannic sumac, a member of the sumac family, also contains polyphenolic compounds. It should be noted that young shoots and leaves collected before the formation of green fruits are of the greatest value. A decoction of raw materials is prescribed for vomiting, nausea, hemoptysis. Infusions are widely used for inflammation in the oral cavity, larynx, pharynx, nose. In addition, sumac tannin is used for wounds as an astringent, antiseptic, and the effectiveness of decoctions and tinctures in the initial phase of diabetes has been established.

At the same time, powdered dry fruits of sumac are used in the Caucasus as a spicy seasoning for meat and meat dishes.