Ethanol: properties and applications. Negative Effects of Ethanol Metabolism Ethyl Alcohol in Medicine

The components of cognac alcohol are divided into substances that are transferred during distillation from wine materials, and into substances formed during aging in oak barrels. The last classification system for these components considers substances that have passed during the distillation of wine materials along with volatile substances, and substances formed during aging - with non-volatile substances.

Volatiles.

The main component of cognac alcohol is ethyl alcohol and water. The rest of the substances should be considered as impurities to these two main components. High-quality cognac alcohol in its composition must have a certain minimum of volatile impurities (otherwise, such cognac alcohol is considered rectified). It should be noted that an excessively large amount of volatile impurities degrades the quality of cognac alcohol.

In cognac alcohols, in addition to ethyl alcohol, a number of other aliphatic alcohols have been found: methanol, propyl, butyl, isobutyl, amyl, isoamyl and other alcohols.

Methyl alcohol (CH4OH) is characterized by the following indicators: molecular weight 32.04; density ρ \u003d 0.7913; melting point 97.7 ° C, boiling point 64.7 ° C.

Methyl alcohol (methanol) is a colorless liquid, in its pure form its smell resembles ethanol, it is miscible with water in any ratio, and it dissolves well in many organic solvents. Methanol is a poisonous liquid, inhalation of its vapors is just as harmful as ingestion. In food products and drinks, no more than 0.1% vol.

In Georgian and Moldovan cognac alcohols, methanol contains from traces to 0.08%. In cognac spirits from red wine materials, the amount of methyl alcohol is noticeably higher (twice or more) than in white ones. Cognac alcohols obtained by the Kakhetian technology (aging on the ridges) contains methanol 296 ... 336 mg / dm3, which is two times higher than from wine materials obtained by European technology (136 ... 288 mg / dm3).

The methanol rectification coefficient is less than one, therefore, during the distillation of cognac wine materials, it passes into the tail fraction. In the process of oxidation with potassium permanganate, methyl alcohol transforms into formic aldehyde, which gives a persistent violet color with fuchsin sulfuric acid (preferably chromotropic acid). This reaction can be used for the qualitative determination of methanol in alcoholic beverages.

Ethyl alcohol (ethanol, C2H5OH) has a molecular weight of 46.07, a density of ρ \u003d 0.789, a boiling point of 78.35 ° C and a melting point of 114.5 ° C. It is the main product of alcoholic fermentation of sugars with a characteristic faint odor, colorless liquid. Mixes with water in any ratio. With a content of 95.57% wt. alcohol boils and is distilled at a constant temperature of 78.15 ° C.

Of the chemical properties of ethyl alcohol, the following reactions should be noted: it easily replaces hydrogen in the hydroxyl group with a metal, easily forms sodium alcoholate and aluminum alcoholate, forms esters with acids, and hemiacetals and acetals with aldehydes. The oxidation of ethanol to acetaldehyde occurs under the action of oxygen soluble in alcohol. Ethyl alcohol is easily oxidized by potassium dichromate, permanganate and other oxidizing agents used in the quantitative determination of alcohol. The solubility of oxygen in alcohol is several times higher than in water (due to the formation of an emulsion). Ethyl alcohol in a vaporous state forms combustible explosive mixtures with air. So when the concentration of alcohol vapors in the air is equal to 3.28%, the mixture explodes. In addition, alcohol vapors, if constantly inhaled, are harmful to the human body. The smell of ethyl alcohol at a concentration of 0.25 mg / dm3 is easily felt in the air.

Higher alcohols.

In winemaking and cognac production, higher alcohols are considered as the sum of aliphatic alcohols with a carbon content of more than three. These are propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl and other alcohols, and their isomers. In wines and cognacs, they are mainly determined in total. Using modern instruments and chromatography, they began to be divided into separate components.

Propyl alcohol (C3H6OH) has a molecular weight of 60.09, density ρ \u003d 0.8036, melting point 126.1 ° C, boiling point 97.2 ° C. It mixes easily with water, ethyl alcohol, benzene and ether.

Butyl alcohol (C4H9OH) has a molecular weight of 74.0, a density of ρ \u003d 0.80978, and a boiling point of 117.4 ° C. It dissolves in cold water up to 9% at 15 ° C.

Isobutyl alcohol (С4Н11ОН) has a molecular weight of 74.0, density ρ \u003d 0.802, boiling point 108.1 ° C. Isobutyl alcohol dissolves in water in an amount of about 10% at a temperature of 15 ° C, it dissolves well in alcohol, ether and benzene.

Amyl alcohol (C5H11OH) has a molecular weight of 88.15, density ρ \u003d 0.814, and a boiling point of 137.8 ° C.

Isoamyl alcohol (С5Н11ОН) - optically inactive, has a molecular weight of 88.15, density ρ \u003d 0.814, boiling point 132.1 оС. It is an oily liquid with a very characteristic unpleasant odor. Vapors of isoamyl alcohol irritate the mucous membrane and cause coughing. It dissolves poorly in water, but dissolves well in ether, alcohol and benzene.

Isoamyl alcohol (С5Н11ОН) - optically active, has a molecular weight of 88.15, a density of ρ \u003d 0.819, a boiling point of 129.4 ° C. It is also an oily liquid with a sharper odor than inactive isoamyl alcohol.

Both isoamyl alcohols make up the most significant part of fusel oils, with slightly less active alcohol.

All higher alcohols are the main irreplaceable components of the volatile impurities of cognac alcohols. Their content ranges from 1000 to 3000 mg / dm3.

The formation of higher alcohols during the fermentation of grape must depends on many factors: the race of yeast, fermentation conditions (aerobic or anaerobic), etc. The pH value has a noticeable effect on the formation of higher alcohols in the fermenting must. At pH 2.6, the minimum amount of higher alcohols was recorded. At pH 4.5, the content of higher alcohols doubles, and with a further increase in pH, the content of higher alcohols decreased slightly.

Significantly affects the formation of higher alcohols and the temperature of the medium (at a fermentation temperature of 15 to 35 ° C). The maximum formation of higher alcohols is established at a temperature of 20 ° C, and at a fermentation temperature of 35 ° C, the amount of higher alcohols decreases four times.

The influence of factors of intensification of yeast growth (biotin, thiamine, pantothenic acid, etc.) depends on the nature of nitrogen sources.

It has now been proven that fusel alcohols are formed not only from amino acids, but also from sugars during their fermentation. So, higher alcohols can be both secondary and by-products of alcoholic fermentation. In general, the formation of higher alcohols depends on the total activity of yeast metabolism.

Thus, in cognac spirit, the higher alcohols have a twofold origin. The first part of them is an integral component of grape essential oils, which first passed into wine materials, and then into cognac alcohol during their distillation. The other part is due to the vital activity of yeast, which forms higher alcohols from both sugar and amino acids as a result of deamination or transamination followed by deamination.

Higher alcohols are toxic substances. This toxicity increases with increasing molecular weight. If the toxicity of ethyl alcohol is taken as a unit, then the toxicity of isobutanol will be four, and that of isoamyl alcohol - 9.25.

With salicylic aldehyde, higher alcohols give a characteristic red color, which is used in their quantitative determination.

Organic acids.

In aged cognac alcohols, the basic acids are non-volatile acids formed during the extraction of oak components (amino acids, tannins, aromatic and polyuronic acids).

The main acids of freshly distilled cognac alcohol are fatty acids: formic, acetic, propionic, butyric, valerian, caproic, enanthic, caprylic, pelargonic, lauric, myristic and other organic acids.

The table below shows a brief description of fatty organic acids in cognac alcohols.

Table Basic acids of freshly distilled fatty cognac alcoholand

Acid name	Chemical formula	Molecular mass	Density, g / cm3, ρ	Melting temperature, oC	Boiling temp, oC	a brief description of
Formic						Colorless liquid with a pungent odor, miscible with water, alcohol, ether
Acetic						Colorless liquid with a characteristic odor, soluble in water, alcohol, ether, benzene
Propionic						Colorless liquid with a pungent odor, soluble in water, alcohol, ether
Oil						Colorless liquid, soluble in alcohol, ether, unpleasant odor
Valerianova						Liquid with a characteristic odor, soluble in alcohol, ether, worse in water
Nylon						Oily liquid with a characteristic odor, dissolves in alcohol and ether
Enanthic						Oily liquid with a characteristic odor
Caprylic						Oily liquid, soluble in alcohol and ether, benzene, chloroform, hot water
Pelargonovaya						Soluble in alcohol, ether, benzene
Capric
Lauric						Colorless needles, soluble in ether, benzene, alcohol. Distilled with water vapor
Myristic

In cognac alcohols, volatile acids contain from 80 to 1000 mg / dm3, and sometimes even more.

In addition to organic acids, there are also mineral acids in cognac spirits and cognacs. Mainly, it is sulphurous and sulfuric, formed during its oxidation. These acids are present in cognac spirits made from sulphitated wine materials. The amount of total sulfurous acid (in terms of SO2) in freshly distilled alcohol can reach 240 mg / dm3.

The pH value in cognac spirits and cognacs varies considerably depending on the technology, type and their age. With fractional distillation, the pH decreases. For example, if the main fraction had a pH of 6.2, then the middle fraction (up to a fortress of 42.5%) has a pH of 4.0, and the tail - 3.2. All this depends on both the acid content and the strength of the alcohol, which inhibits the dissociation of carboxylic acid groups. Therefore, in stronger aqueous-alcoholic solutions, the pH value of the same acidity is higher than in weak solutions.

The pH changes most dramatically in cognac spirits and cognacs in the first two years of aging. Starting from 10 years of aging, the pH practically does not change in the range of 4.1 ... 4.0.

Esters.

The main part of esters in cognac spirits and cognacs are ethyl esters of fatty acids, the content of which, in most cases, ranges from 300 to 1600 mg / dm3. These mainly include ethyl formate and ethyl acetate.

Ethyl formate (C3H6O) has a molecular weight of 74, a density of 0.91678 g / cm3, and a boiling point of 54.3 ° C. It dissolves easily in water at a temperature of 25 ° C.

Ethyl acetate (ethyl acetate) (C4H8O2) has a molecular weight of 88.10, a density of 0.9006 g / cm3, a melting point of 83.6 ° C, and a boiling point of 77.1 ° C. It is a colorless liquid with an ethereal-fruity odor. Mixes up in any ratio with many organic solvents (alcohol, ether, benzene, etc.).

In addition to these esters, the following ethyl esters of fatty acids were found in cognac alcohols and cognacs: ethyl propianate (C7H12O), ethyl butyrate (C7H12O2), ethyl valerianate (C7H14O2), ethyl capronate (C8H16O2), ethyleneanthate, C9H128O2) dr.

In addition to ethyl esters of fatty acids, esters of propyl, butyl, amyl, and hexyl alcohols and their isomers were found in cognac alcohols.

Both in cognac spirits and cognacs, the main component of esters is ethyl acetate and enanthic ether, which are formed mainly by yeast during fermentation. Depending on the yeast race or fermentation conditions, the amount of enanth ester may vary. In general, the content of esters in eaux-de-vie and cognacs depends on the concentration of acids and alcohols.

A very important property of esters is their ability to saponify under the action of alkalis, which is used for their quantitative determination.

It should be noted that in this case ethyl acetate is saponified much more easily than esters of more high-boiling acids, which is used to determine enanth esters in cognac alcohols. With hydroxylamine, esters form hydroxamates, which give a characteristic dark blue color in the presence of ferric iron.

Aldehydes and acetals.

The amount of volatile aldehydes (aliphatic) in cognac spirits is in the range of 50 ... 500 mg / dm3 of absolute alcohol. In general, such volatile aldehydes as acetic, propionic, isobutyric and isovaleric aldehydes are found in significant quantities in cognac alcohols.

Acetaldehyde (acetaldehyde, ethanal) (C2H4O) has a molecular weight of 44.05; density ρ \u003d 0.783 kg / dm3, melting point - 122.6 ° C, boiling point - 20.8 ° C. It is a colorless, easily mobile liquid with a pungent characteristic odor, easily mixed with water, alcohol and ether. Reacts with sodium bisulfite and sulfur dioxide.

Propionaldehyde (C3H6O) has a molecular weight of 58.08; density ρ \u003d 0.807 kg / dm3, melting point - 81 ° C, boiling point - 49.1 ° C. It is a liquid with a suffocating odor, mixes with alcohol and ether, slightly soluble in water.

Isobutyraldehyde (C4H8O) has a molecular weight of 72.0; density ρ \u003d 0.794 kg / dm3, boiling point - 64 ° C.

Isovaleric aldehyde (C5H10O) has a molecular weight of 86.13; density ρ \u003d 1.39 kg / dm3, melting point - minus 51 ° C, boiling point - 92.5 ° C.

All aldehydes in aqueous solutions add water, so they do not absorb light in the ultraviolet region of the spectrum. A very important property of aldehydes is their reaction with bisulfite and sulfurous acid. Aldehydes are very sensitive to the action of oxidizing agents, and they are also capable of self-oxidation with the formation of carboxylic acids.

A characteristic reaction for aldehydes and acids is their interaction in an acidic medium with 2,4-dinitrophenylhydrazine to form 2,4-dinitrophenylhydrazone, which gives a strong red color in an alkaline medium. This reaction can be used to quantify aldehydes.

In cognac alcohols, the total content of aliphatic aldehydes ranges from 30 to 300 mg / dm3. The main part of them is vinegar. In addition, crotonic, propionic, isobutyric and valerian aldehydes are found in cognac spirits.

With the aging of cognac spirits, only the content of acetaldehyde increases, the content of other aliphatic aldehydes decreases.

Aldehydes with cognac alcohols form acetals with the release of two water molecules. The stability of acetals in an alkaline medium is much higher than in an acidic medium, where they are quickly saponified to the initial aldehydes and alcohols.

In general, the formation of acetals and hemiacetals in cognac spirits softens the harsh tones in the cognac bouquet.

According to the law of action of the masses, in cognac spirits and cognacs, the main factor influencing the concentration of acetals is the alcohol content.

The most important volatile compounds affecting the quality indicators of cognac are butylene glycol, acetoin and diacetyl, the amount of which in cognac spirits is: butylene glycol - 6.1 mg / dm3; acetoin - 4.6 mg / dm3 and diacetyl - 1.6 mg / dm3. Cognac spirits also contain volatile amines, which are tail impurities in the distillation of wine materials.

Non-volatile substances (extractives) of cognac spirits are components extracted from oak barrels and products of their chemical transformations. The amount of non-volatile substances in cognac spirits depends on the temperature of the alcohols during storage, the holding time in barrels, the capacity of the barrels, the composition of different alcohols and a number of other factors.

French cognacs contain extractive substances from 4.5 to 12 g / dm3, Armenian - from 9.86 to 9.62 g / dm3, Italian - up to 21.5 g / dm3, Georgian (aged from 2 to 22 years) - from 1.5 to 6.0 g / dm3.

During the aging of cognacs, extractive substances undergo various chemical transformations, forming a number of volatile products, such as aldehydes, acids, etc.

When cognac spirits are aged in an oak barrel, the alcohol macerates the oak lignin and its decomposition products (aromatic aldehydes and acids), which subsequently undergo various decomposition and polymerization reactions. The products of further transformation of lignin into cognac spirit are very diverse. Depending on the solubility in water and ether, as well as volatility, the lignin complex of cognac spirits is divided into a number of fractions:

· Non-volatile, water - and ether-soluble;

· Non-volatile water-soluble, ether-insoluble;

· Volatile, water - and ether-soluble;

· Ether-soluble, water-insoluble;

Water insoluble, etc.

Water-insoluble lignin is that part of the products of maceration from oak stave that precipitates when diluted with alcohol (water-insoluble fraction). The elemental composition of such lignin is as follows: hydrogen - 5.67%; carbon - 59.09%; methoxyl groups - 11.38% (data from Egorov I.A. and Skurikhin I.M.)

The water-soluble fraction of the lignin complex of cognac alcohol is 85% of the total. This fraction includes various glucosides, hemicetals and ethers (aromatic components of lignin). Water-soluble substances of the lignin complex of cognac alcohol are easily oxidized by permanganate in the determination of tannins.

About 30% of the lignin complex of cognac alcohol is represented by substances that are soluble in ether. The composition of these substances includes a number aromatic aldehydes (vanillin, syringaldehyde, hydroxybenzaldehyde, conifryl aldehyde, sinapic aldehyde) and aromatic acids (vanillic acid, syringic acid, hydroxybenzoic acid). Let's briefly consider their characteristics.

Vanillin (С8Н8О3) has a molecular weight of 152, density ρ \u003d 1.056, melting point 81.2 ° C, poorly soluble in water, easily soluble in alcohol, chloroform, ether, carbon disulfide and alkali solutions. Has a dark blue fluorescence.

Lilac aldehyde (C9H10O4) has a molecular weight of 182, a melting point of 113 ° C, dissolves in ether, ethanol, chloroform, acetic acid, hot benzene, heavily in water and naphtha, does not dissolve in petroleum ether. The salts of lilac aldehyde, potassium and sodium are yellow, soluble in water and alcohol.

Oxybenzaldehyde (С7Н6О2) has a molecular weight of 122, a melting point of 116 ° C, easily crystallizes from water, dissolves in hot water, ethanol, ether, does not dissolve in cold water.

Conifryl aldehyde (C10H10O3) has a molecular weight of 178, a melting point of 82.5 ° C, crystallizes from benzene, dissolves in methanol, ethanol, ether, chloroform, and dissolves in naphtha. Gives green fluorescence.

Sinapaldehyde (С11Н12О4) has a molecular weight of 208, a melting point of 108 ° C, is easily soluble in alcohol and acetic acid, and practically insoluble in water, benzene and ether. It dissolves in concentrated mineral acids with the formation of a blue-red color. Gives green fluorescence.

In general, aromatic aldehydes are critical to the aroma of aged cognacs. They give a number of characteristic color reactions (the most famous reaction with phloroglucinol in hydrochloric acid).

Aromatic acids appear as a result of oxidation of aromatic aldehydes in cognac alcohols. This is vanillic acid with a molecular weight of 168 and a melting point of 207 ... 210 ° C, readily soluble in ethanol and ether; lilac acid with a molecular weight of 198 and a melting point of 204.5 ° C, readily soluble in ether, ethanol and chloroform; hydroxybenzoic acid with a molecular weight of 138, density ρ \u003d 1.443 kg / dm3, melting point 215 ° C.

All aromatic acids react strongly with Volin-Denis reagents. In three-year-old cognac alcohol, the amount of vanillic and lilac acids is 0.16 mg / dm3 each, in fifteen-year-old cognac alcohol it sharply increases and reaches 0.5 mg / dm3 each.

Tannins (tanidi). There are comparatively few of these substances in cognac spirit even after long aging in oak barrels (up to 0.25 g / dm3). But cognac spirits contain a large amount of substances similar in chemical composition to tannins. All of them are united by the presence of pyrogallic hydroxyl groups and have a common name: tannins of cognac alcohol.

Skurikhin I.M. in his experiments proved that tannins in cognac spirits can be not only in a free position, but also associated with lignin, and the tannins of cognac alcohols do not represent a homogeneous complex.

Depending on the ability to adsorb leather powder and on the solubility in aqueous solutions, tannins are divided into three fractions:

1. Water-insoluble, easily separated from solution after distillation of alcohol. Their number is 20 ... 36% of the amount of tannins dissolved in cognac alcohol.

2. Water-soluble, which remain in solution after distillation of alcohol and are adsorbed by leather powder. Their number is 36 ... 60% of the total amount of cognac alcohol tannides.

3. Water-soluble, not absorbed by leather powder. Their number is 20 ... 30% of the amount of tannins.

In cognac alcohols, as a result of hydrolysis of tannins, ellagic and gallic acids appear in noticeable quantities. The properties of these acids are characterized by the following data:

Elagic acid (C14H6O8) has a molecular weight of 302, a melting point of 360 ° C. The acid is hardly soluble in water and alcohol, insoluble in ether, with FeCl3 it gives a green color. The acid is formed during the hydrolysis of oak tannins.

Gallic acid (C7H6O5) has a molecular weight of 170, crystallizes from water with one water molecule, is insoluble in chloroform, benzene. Gallic acid has an antioxidant effect on terpenes and fatty oils, and is a permanent accompanying component of oak wood.

Carbohydrates and products of their transformations. Carbohydrates and products of their transformations in cognac alcohols are represented by the simplest monosaccharides - fructose, glucose, xylose, arabinose, rhamnose, mannose and a small amount of dextrins. In addition, when blending brandy, color (product of sucrose caramelization) and sucrose are added.

Fructose (C6H12O6) is a keto alcohol, has a molecular weight of 180, a melting point of 102 ... 104 ° C, and a density of ρ \u003d 1.669 kg / dm3. One of the forms of fructose, fructopyranose, can exist in two modifications: α and β-forms. The crystals always contain β-D-fructose. In aqueous solutions, D-fructose is presented in the form of fructopyranose and fructofuranose.

Glucose (C6H12O6) - has a molecular weight of 180, a melting point of 146 ° C, and a density of ρ \u003d 1.544 kg / dm3. It is a polyhydric aldehyde alcohol.

The aldehyde form of glucose has four asymmetric carbon atoms, while in the cyclic form a fifth asymmetric atom appears. Therefore, D-glucose can exist in two modifications: α and β-forms. α-D-glucose is less soluble in water, while β-D-glucose is more soluble in water.

Like all other monosugars, glucose is a powerful reducing agent. Heating glucose in solutions of mineral acids leads to the loss of three water molecules and the formation of oxymethylfurfural, an oily liquid with the smell of overripe apples, which has strong restorative properties. Further, this substance decomposes into levulinic and formic acids.

Xylose (C5H10O5) - has a molecular weight of 150.13, a melting point of 154 ° C, and a density of ρ \u003d 1.535 kg / dm3. It is a crystalline substance, half as sweet as sucrose. Xylose reduces Felling liquid to the same extent as glucose, and when boiled with dilute mineral acids, it gives furfural.

Arabinose (C5H10O5) is characterized as a reducing agent of Felling liquid with the formation of copper oxide. Molecular weight 150.13, melting point 160 ° C, density ρ \u003d 1.585 kg / dm3. Arabinose is a crystalline substance that tastes less sweet than glucose. Under the action of dilute mineral acids, it loses three water molecules and forms furfural.

Rhamnose (C6H12O5) crystallizes from one water molecule, has a molecular weight of 182.17; rhamnose hydrate melts at a temperature close to 93 ... 97 ° C, and anhydrous rhamnose - at 122 ... 126 ° C. Rhamnose dissolves poorly in ether, but well in water and alcohol. In air, anhydrous rhamnose absorbs water and turns into monohydrate. Rhamnose tastes sweet, but sucrose is three times as sweet and glucose is twice as sweet.

Sucrose (С12Н22О11) is an integral part of cognac blending. Molecular weight 342.3, melting point 184 ... 185оС, density ρ \u003d 1.583 kg / dm3. It is a disaccharide that is broken down by dilute mineral acids or the invertase enzyme into a mixture of equal amounts of D-glucose and D-fructose (invert sugar).

Sucrose is a colorless crystalline substance with a sweet taste. Molten sucrose, when cooled, solidifies into a glassy mass. Sucrose breaks down to a substance that does not crystallize (caramel) above its melting point.

In ether and chloroform, sucrose is insoluble, but it is readily soluble in water, in absolute alcohol it is slightly soluble, in water-alcohol solutions it is better.

Kohler is a product of sucrose caramelization at a temperature of 180 ... 200 ° C, ie, above the melting point of sucrose. During caramelization, sucrose is dehydrated with the formation of various polymer products: caramel, organic acids and other compounds. The color of the color scheme does not depend on the colorless sucrose anhydrides, but on the humic acids that are formed in this case. Kohler contains from 35 to 60% sugar. It dissolves well in cognac alcohol and water. When diluted 1 ml in 1 liter of water, its color should correspond to the color of 10 ml of 0.1 N iodine in 1 liter of water. The density of the color scheme is 1.3 ... 1.4 kg / dm3.

If sucrose is not found in cognac alcohols, then in cognacs (as a result of the addition of sugar syrup) its content is up to 25 g / dm3. Kohler is mainly added only to ordinary cognacs.

Furan aldehydes... Of these aldehydes, furfural, methylfurfural and oxymethylfurfural were found in cognac spirits.

Furfural (С5Н4О2) has a molecular weight of 96.08, a density ρ \u003d 1.1598 kg / dm3, a melting point of 38.7 ° C, and a boiling point of 161.7 ° C. It is a colorless liquid with a characteristic odor, readily soluble in alcohol and ether. During storage, furfural slowly decomposes with the formation of formic acid and brown humic substances. Furfural in an acidic medium gives a characteristic pink color with aniline. This color reaction is used for quantification.

Methylfurfural (C6H6O2) has a molecular weight of 110.0, a density of ρ \u003d 1.1072 kg / dm3, and a boiling point of 187 ° C. It dissolves easily in thirty parts of water.

Oxymethylfurfural (С6Н6О3) has a molecular weight of 126, a melting point of 35 ... 35.5 ° C, and a boiling point of 114 ... 116 ° C. It dissolves well in ethanol, water, ethyl acetate. Formed by hydration of glucose and fructose.

Mineral and other substances. On average, in cognac alcohols, the ash content ranges from 0.034 g / dm3 and higher, in young cognac spirits up to 0.118 g / dm3, in old ones (more than 20 years old) about 1% of the extract.

The composition of the ash elements of cognac spirits and cognacs in many cases depends on the composition of the oak tree. One can expect the presence of K, Ca, Na, Mg, Cl, P, Si, etc. During the distillation of wine materials, due to contact with copper and iron apparatus, a noticeable amount of iron and copper passes into cognac alcohol. Cognac spirits stored in uncoated aluminum tanks can contain up to 20 mg / dm3 of aluminum, which negatively affects the taste and aroma of alcohols.

With the aging of cognac alcohols, a natural increase in extractives and ash occurs, the ash content (% ash in the extract) decreases, which is due to the precipitation of a number of elements that make up the mineral substances. The amount of elements such as Cu, Fe, Mg decreases noticeably during aging of cognac alcohols, which is explained by their precipitation in the form of sparingly soluble salts of tannic and organic acids. The content of К і Na increases as a result of extraction from oak wood and concentration due to the evaporation of alcohol from barrels during aging.

According to the current technological instructions, the following amount of heavy metals is allowed in cognac spirits and cognacs: lead - not allowed, iron - no more than 1 mg / dm3, tin - no more than 5 mg / dm3 and copper - no more than 8 mg / dm3.

In addition to minerals, cognac spirits also contain nitrogenous substances, the amount of which is about 2% of the extractive substances of alcohols. Thus, in 24-year-old cognac alcohol, the total nitrogen content reaches 82 mg / dm3. Among the nitrogenous substances in cognac alcohols, such amino acids as glycocol, glutamic acid, proline, etc. prevail.

ACETALDEHYDE, acetaldehyde, ethanal, CH 3 · CHO, is found in raw wine alcohol (formed during the oxidation of ethyl alcohol), as well as in the first shoulder straps obtained during the rectification of wood alcohol. Previously, acetaldehyde was obtained by oxidizing ethyl alcohol with dichromate, but now they switched to the contact method: a mixture of ethyl alcohol vapor and air is passed through heated metals (catalysts). Acetaldehyde resulting from the distillation of wood alcohol contains about 4-5% of various impurities. The method of extracting acetaldehyde by decomposing lactic acid by heating it is of some technical importance. All these methods for producing acetaldehyde are gradually losing their importance in connection with the development of new, catalytic methods for producing acetaldehyde from acetylene. In countries with a developed chemical industry (Germany), they gained predominance and made it possible to use acetaldehyde as a starting material for the production of other organic compounds: acetic acid, aldol, etc. The basis of the catalytic method is the reaction discovered by Kucherov: acetylene in the presence of mercury oxide salts adds one particle of water and turns into acetaldehyde - CH: CH + H 2 O \u003d CH 3 · CHO. To obtain acetaldehyde under a German patent (chemical factory Griesheim-Electron in Frankfurt am Main), acetylene is passed into a solution of mercuric oxide in strong (45%) sulfuric acid, heated to no higher than 50 ° C, with strong stirring; the resulting acetaldehyde and paraldehyde are periodically siphoned off or distilled off in a vacuum. The best, however, is the method claimed by French patent 455370, in which the plant of the Electrical Industries Consortium in Nuremberg operates.

There, acetylene is passed into a hot, weak solution (not higher than 6%) of sulfuric acid containing mercury oxide; Acetaldehyde formed during this process is continuously distilled and condensed in certain receivers. According to the Grisheim-Electron method, some of the mercury formed as a result of the partial reduction of the oxide is lost, since it is in an emulsified state and cannot be regenerated. The Consortium's method in this respect is a great advantage, since here mercury is easily separated from the solution and then electrochemically converted into oxide. The yield is almost quantitative and the acetaldehyde obtained is very pure. Acetaldehyde is a volatile, colorless liquid, boiling point 21 °, specific gravity 0.7951. It mixes with water in any ratio; it is released from aqueous solutions after adding calcium chloride. Of the chemical properties of acetaldehyde, the following are of technical importance:

1) The addition of a drop of concentrated sulfuric acid causes polymerization with the formation of paraldehyde:

The reaction proceeds with a lot of heat. Paraldehyde is a liquid boiling at 124 ° C and does not exhibit typical aldehyde reactions. When heated with acids, depolymerization occurs, and acetaldehyde is obtained back. In addition to paraldehyde, there is also a crystalline polymer of acetaldehyde - the so-called metaldehyde, which is probably a stereoisomer of paraldehyde.

2) In the presence of some catalysts (hydrochloric acid, zinc chloride and especially weak alkalis) acetaldehyde is converted into aldol. Under the action of strong caustic alkalis, the formation of an aldehyde resin occurs.

3) Under the action of aluminum alcoholate, acetaldehyde is converted into ethyl acetate (Tishchenko reaction): 2CH 3 · CHO \u003d CH 3 · COO · C 2 H 5. This process is used to produce ethyl acetate from acetylene.

4) Addition reactions are of particular importance: a) acetaldehyde attaches an oxygen atom, while converting into acetic acid: 2CH 3 · CHO + O 2 \u003d 2CH 3 · COOH; oxidation is accelerated if a certain amount of acetic acid (Grisheim-Electron) is added to acetaldehyde in advance; the most important are catalytic oxidation methods; the catalysts are: iron oxide-oxide, vanadium pentoxide, uranium oxide, and especially manganese compounds; b) adding two hydrogen atoms, acetaldehyde is converted into ethyl alcohol: CH 3 · CHO + H 2 \u003d CH 3 · CH 2 OH; the reaction is carried out in a vapor state in the presence of a catalyst (nickel); under some conditions, synthetic ethyl alcohol competes successfully with alcohol produced by fermentation; c) hydrocyanic acid joins acetaldehyde, forming lactic acid nitrile: CH 3 CHO + HCN \u003d CH 3 CH (OH) CN, from which lactic acid is obtained by saponification.

These diverse transformations make acetaldehyde one of the most important products of the chemical industry. Its cheap production from acetylene has recently made it possible to carry out a number of new synthetic productions, of which the method of producing acetic acid is a strong competitor to the old method of obtaining it by dry distillation of wood. In addition, acetaldehyde is used as a reducing agent in the production of mirrors and is used to prepare quinaldine, a substance used to obtain paints: quinoline yellow and red, etc .; in addition, it serves for the preparation of paraldehyde, which is used in medicine as a hypnotic.

Publication in print media: Topical issues of forensic medicine and law, Kazan 2010 Vol. 1 GKUZ "Republican Bureau of Forensic Medical Examination of the Ministry of Health of the Republic of Tatarstan"

Forensic medical diagnosis of the cause of death in cases of alcohol intoxication often causes serious difficulties. This, first of all, applies to those cases when there are no sufficiently pronounced changes in the internal organs, and the concentration of ethanol in the blood is either insignificant, or it is not detected at all. In such situations, the detection of ethanol oxidation products, in particular acetaldehyde, can serve as objective evidence of alcohol intoxication, since it serves as one of the causes of a hangover, remaining in the body for a long time.

Acetaldehyde (AC) - acetaldehyde, an organic compound, an easily volatile colorless liquid with an asphyxiant odor, miscible in all respects with water, alcohol, ether. AC has all the typical properties of aldehydes. In the presence of mineral acids, it polymerizes into liquid trimeric paraldehyde and tetrameric metaldehyde. Vapors are heavier than air and oxidize in air to form peroxides. Acquires a fruity odor when diluted with water. They are used on a huge scale in the production of acetic acid, acetic anhydride, various pharmaceuticals, etc. ...

In the human body, endogenous ethanol is constantly present, which is formed in biochemical processes. The source of endogenous ethanol is endogenous acetaldehyde, which is a product of carbohydrate metabolism, which is formed mainly as a result of decarboxylation of pyruvate with the participation of the corresponding enzyme of the pyruvate dehydrogenase complex. According to the literature, the concentration of endogenous ethanol in the blood of healthy people averages 0.0004 g / l; the maximum values \u200b\u200bdo not exceed hundredths of a g / l, the concentration of endogenous acetaldehyde is 100-1000 times lower. AC is the main intermediate metabolite of ethanol. The main route is with the participation of alcohol dehydrogenase according to the scheme:

C 2 H 5 OH + NAD + ↔ CH 3 CHO + NADH + H +.

The formed AC is oxidized by aldehyde dehydrogenase (ADH) to acetate. Within 1 hour, 7-10 g of alcohol can be metabolized in the human body, which corresponds to a decrease in its concentration by an average of 0.1-0.16 ‰. Oxidative processes can be activated and reach 0.27 ‰ / h. The duration of toxicodynamics is determined, first of all, by the amount of alcohol consumed. When taking large amounts of AC, it can persist in the body for 1 day or longer. Within 1-2 hours after taking blood from living persons, enzymatic oxidation of alcohol stops, as well as after death occurs in the blood of corpses. The main place of formation of AC from ethanol and its subsequent oxidation is the liver. Therefore, the greatest amount of acetaldehyde in the experiments was determined in the liver, then in the blood, the smallest - in the cerebrospinal fluid.

AC identification in biological objects was carried out on a Kristalluks-4000M gas chromatograph equipped with a NetchromWin computer program and a flame ionization detector on capillary columns. Three capillary columns were used:

column # 1 30m / 0.53mm / 1.0µ, ZB - WAX (Polyethylen Glycol);
column # 2 30m / 0.32 mm / 0.5µ, ZB - 5 (5% Penyl methyl polysiloxane);
column # 3 50 m / 0.32 mm / 0.5µ, HP - FFAP.

Column temperature 50 ° C, detector temperature 200 ° C, evaporator temperature 200 ° C. The flow rate of the carrier gas (nitrogen) 30 ml / min, air 500 ml / min, hydrogen 60 ml / min.

Good separation of the mixture was noted (Fig. 1): acetaldehyde + diethyl ether + acetone + ethyl acetate + ethanol + acetonitrile.

Figure: 1. Distribution of substances.

Acetone, methanol, ethanol and other aliphatic alcohols, ethyl acetate, organochlorine compounds, aromatic hydrocarbons, diethyl ether do not interfere with the detection and determination of acetaldehyde (Table 1).

Table 1. Comparative results of identification of acetaldehyde in a mixture with other substances

Column # 3 HP - FFAP was not used for quantitative analysis, as such analysis is time-consuming and economical.

Construction of a calibration graph for acetaldehyde. To plot the calibration graph, we used aqueous solutions of acetaldehyde (chemically pure for chromatography) with a concentration of 1.5; fifteen; thirty; 60; 150 mg / l. The internal standard is an aqueous solution of acetonitrile with a concentration of 78 mg / L.

Research method: in a glass vial containing 0.5 ml of a 50% solution of phosphoric-tungstic acid, 0.5 ml of an internal standard - a solution of acetonitrile with a concentration of 78 mg / L and 0.5 ml of a solution of acetaldehyde with a known concentration - were placed. To reduce the partial pressure of water vapor, 2 g of anhydrous sodium sulfate were added to the mixture. The vial was closed with a rubber stopper, fixed with a metal clip, heated in a boiling water bath for 5 minutes, and 0.5 ml of a warm vapor-gas phase was introduced into the chromatograph evaporator. The sensitivity factor was calculated (Table 2) for 2 columns:

Table 2. Calculation of the sensitivity factor

A ac, mg / l	Column No. 1		Column No. 2
A ac, mg / l	Sх, in mv / min	Sst, in mv / min	Sх, in mv / min	Sst, in mv / min
150	69	10	15	2
60	39	11	4.5	1.7
30	24	14	3	2
15	10	12	1.2	1.5
1,5	1.2	15	0.18	2

Abbreviations: And ac - concentration of acetaldehyde; Sх - peak area of \u200b\u200bacetaldehyde; Sst is the peak area of \u200b\u200bacetonitrile.

Figure: 2. Graph of the dependence of the ratio of areas on the concentration of acetaldehyde for the 1st column.

According to the above-described technique, studies were carried out from biological objects (blood, urine, brain matter, liver, kidney, etc.).

Investigated 40 cases with suspected poisoning "alcohol substitutes". The results of the study of these cases are summarized in Table 3.

Table 3. Distribution of ethanol

Case from practice: the corpse of a 40-year-old man from the intensive care unit was delivered. The patient was in the hospital for 4 hours, in the anamnesis for treatment "Esperal" was used. In the process of forensic chemical research of biological objects, disulfiram and other medicinal substances were not found. Ethyl alcohol was not found in the blood. Found AC with a concentration of 0.5 mg / L in the blood, 28 mg / L in the stomach, 2 mg / L in the liver, 1 mg / L in the kidney, 29 mg / L in the intestine.

With the simultaneous use of ethyl alcohol and disulfiram (teturam), AC is formed. The mechanism is that disulfiram inhibits the enzyme alcohol dehydrogenase, delaying the oxidation of ethanol at the AC level, which leads to intoxication of the human body. Some drugs can have teturam-like activity, causing alcohol intolerance. These are, first of all, chlorpropamide and other antidiabetic sulfa drugs, metronidazole, etc., derivatives of nitro-5-imidazole, butadione, antibiotics.

findings

A modern highly sensitive gas chromatograph "Kristalluks-4000M" with a DIP detector and a computer program "NetchromWin", which allows determining low concentrations of AC close to endogenous, was used.
New selective, highly sensitive capillary columns with ZB-WAX, ZB-5 phases have been proposed, which make it possible to detect up to 100 μg (0.001% o) acetaldehyde in the samples under study.
Optimal conditions have been selected that allow gas chromatographic screening of acetaldehyde and the following organic solvents: aliphatic alcohols, organochlorine solvents, aromatic hydrocarbons, ethyl acetate, acetone, and diethyl ether for 15 minutes.
It is recommended to carry out a quantitative determination of both ethanol and acetaldehyde in the diagnosis of "alcohol intoxication".

List of references

Albert A. // Selective toxicity. - M., 1989. - T.1 - S. 213.
R. Morrison, R. Boyd // Organic Chemistry, trans. from English-1974-78
Savich V.I., Valladares H. Agusakov., Yu.A., Skachkov Z.M. // Judgment-honey. expert. - 1990. - No. 4. - S. 24-27.
Uspensky A.E., Listvina V.P. // Farmakol. and toxicol. - 1984. - No. 1. - S. 119-122.
Shitov L.N. Research methods and toxicology of ethyl alcohol (chemical-toxicological laboratory of YaOKNB). - 2007.

UDC 577.1: 616.89

ENDOGENOUS ETHANOL AND ACETALDEHYDE,

THEIR BIOMEDICAL VALUE (Literature review)

Yu. A. Tarasov, Ph.D. n., s.n.s.; V.V. Lelevich, Doctor of Medical Sciences, Professor

EE "Grodno State Medical University"

The review presents literature data on the metabolism of endogenous ethanol and acetaldehyde in the body, as well as their biological significance.

Key words: endogenous ethanol, acetaldehyde, alcohol dehydrogenase, aldehyde dehydrogenase, pyruvate dehydrogenase.

The review presents the literature data on the metabolism of endogenous ethanol and acetaldehyde in the organism, as well as their biological value.

Key words: endogenous ethanol, acetaldehyde, alcohol dehydrogenase, acetaldehyde dehydrogenase, pyruvate dehydrogenase.

While characterizing the biological activity of ethanol and its metabolite, acetaldehyde, two aspects of the problem should be emphasized. First, when it comes to these compounds, as natural metabolites, constantly (endogenously) present in the body in physiological concentrations. Secondly, when a situation arises with the exogenous intake of alcohol into the body, that is, the formation of states of acute or chronic alcohol intoxication.

Ethanol and its metabolites are natural components of metabolism and are irreplaceable participants in homeostatic mechanisms. To assess the metabolic significance of endogenous ethanol, its level in blood and tissues should be compared with the content of known substrates - participants in metabolism in humans and animals (see table). This makes it possible to make sure that, given the relatively low molecular weight of ethanol, it can easily be placed on a par with the intermediate products of carbohydrate and protein metabolism. From the data presented in the table, it follows that the concentration of the neurotransmitter is several orders of magnitude lower than endogenous ethanol. But the content of acetaldehyde, which is constantly present in the body in equilibrium (1: 100) with ethanol, is quite comparable with it. This suggests that the role of the ethanol / acetaldehyde pair in maintaining homeostatic metabolic functions is similar to that of the glucose / glucose-6-phosphate and lactate / pyruvate ratios in the body in controlling glycolysis reactions and stabilizing the levels of glycolysis intermediates.

The amount of pyruvate in the tissues is 2-3 orders of magnitude lower than lactate, but pyruvate itself, like acetaldehyde, is highly reactive. With changing metabolic situations, the level of pyruvate shifts significantly

Compound Blood (mol / L) Liver (mol / kg)

Glucose 5 - 10 - 3

Glucose-6-phosphate 2 ■ 10- 4

Fructose-6-phosphate 2 ■ 10-4

Phosphodioxyacetone 10-5 - 10-4 10-4

Amino acids 10-4 - 10-3

Ethanol 10- 4 10- 4

Adrenaline 10-9

less than the level of lactate, which undoubtedly reflects the greater importance in the metabolism of the first rather than the second compound. Therefore, lactate is regarded as a buffer metabolic dead end, leveling fluctuations in pyruvate. From the same standpoint, the ethanol / acetaldehyde system is a similar control point for bicarbon compounds and acetaldehyde itself. Such an assessment of the ethanol / acetaldehyde relationship quite satisfactorily explains the lability of the endogenous ethanol level under a variety of influences. Thus, endogenous ethanol acts as a buffer in equilibrium dynamic relations with its very active precursor, acetaldehyde. The considered para-ethanol / acetaldehyde (see figure) performs similar functions of a buffer pool in relation to a very active, especially in relation to neurohormones, metabolite-acetaldehyde. Ethanol works in this system as a buffer reserve for acetaldehyde, leveling fluctuations that inevitably arise due to the sinusoidal nature of the course of multi-link chain reactions in metabolism.

Carbohydrates, lipids, amino acids

Lactate □ pyruvate □ acetyl-CoA

Ethanol □ acetaldehyde □ acetate

Other sources

Figure - Lactate and ethanol as metabolic "dead ends" in the exchange of pyruvate and acetaldehyde

The heterogeneity of the functions of endogenous ethanol, which can be very different, is a source of energy, a precursor of acetaldehyde, which is involved in the synthesis of endogenous morphine-like compounds, and is the strongest modifier of amine and sulfhydryl groups in proteins. Acetaldehyde, as a powerful modifier of proteins, changes not only their reactivity, but also spatial characteristics, that is, the parameters that are most important for the effective binding of neurotransmitters by receptor proteins. The diphilic nature of ethanol and acetaldehyde plays a significant role in maintaining a certain hydrophobicity of proteins and the required functional fluidity of the latter.

Both compounds are considered as bicarbon radicals capable of competitively interacting with many other bicarbon molecules at the level of active centers of enzymes, transport proteins, and specific receptors. The membranotropy of ethanol is functionally important in the pathogenesis of manifestations of alcoholic illness, since various diols, moreover, which do not form acetaldehyde, are able to relieve the manifestations of ethanol withdrawal. The ethanol / acetaldehyde vapor may be of particular importance in its relationship with hydroxyl or carbonyl groups containing neurotransmitters, hormones, their precursors and metabolites, since the concentration of these bioregulators is much lower than the concentration of endogenous ethanol and acetaldehyde.

The amount of endogenously formed and metabolized acetaldehyde and ethanol, therefore, should be considered as a factor controlling a significant part of the homeostatic mechanisms that ultimately form the state to which any organism always strives - “metabolic comfort”.

Repeated many times in different seasonal periods of the year, the selection of animals in relation to their consumption of ethanol solutions always made it possible to isolate rats that prefer water (PV) or ethanol (PE) from the general population. PEs accounted for approximately 5-10% of all animals tested. A distinctive feature of PE of individuals was that the content of endogenous ethanol in the blood, and, especially, in the liver, was always 2-3 times lower in them than in PV. In turn, the discovered inverse correlations between the level of endogenous ethanol and voluntary alcohol consumption, in essence, repeat the pathogenetic situation: the value of endogenous ethanol and acetaldehyde is such that, with their deficiency in the body, additional alcohol intake becomes the simplest way of self-correction. In turn, the extrapolation of these relationships to the mechanisms of the pathogenesis of alcoholism makes it possible to believe that prolonged excessive consumption of alcohol, forced in an experiment on animals and voluntary or socially motivated in humans, eventually replacing the production of endogenous ethanol and acetaldehyde, leads first to inhibition, and then to the degradation of the systems of endogenous synthesis of these compounds. That is, to a situation where the external intake of alcohol into the body becomes necessary. To a large extent, naturally, in a simplified way, without taking into account the drug addiction factor in pathogenesis, such relationships can explain the phenomenon of physical dependence, as well as an understanding of why, in delirious conditions, the best and simplest way to stop them is to administer alcohol to the patient.

The relationship between alcohol motivation and the level of endogenous ethanol can be traced in other experimental situations. Thus, various factors influencing the consumption of alcohol by animals or the drugs used for treatment, according to their effect on the level of endogenous ethanol in the blood and liver, were divided into two diametrically opposite groups. All effects that enhance alcoholic motivation, such as: stress, starvation, oxythiamine, iproniazide, tetra-hydroisoquinolines - reduce, and weakening alcoholic motivation (thiamine, thiamine diphosphate, riboflavin, diethyldithiocarbamate, glutamine, lithium chloride) -

increase the level of endogenous ethanol. These data are supplemented by studies of other authors in relation to tranquilizers, castration and experiments in which rats, differently sensitive to the narcotic effect of ethanol, also differed in the level of endogenous ethanol. Determination of the level of endogenous ethanol is used in drug treatment clinics in Poland for dynamic control of the applied therapeutic treatment of patients with alcoholic disease. In the clinic for alcohol addiction therapy at the St. Petersburg Psychoneurological Institute VM Bekhterev successfully used a method of treating alcoholism, based on restoring the homeostasis of endogenous ethanol in the patient's body.

It should be noted that the listed variants of the manifestation of the activity of ethanol and acetaldehyde are important not only in acute and chronic alcohol intoxication, but, which is paramount, in natural conditions, in the endogenous functioning of compounds. At the same time, in assessing the biological activity of ethanol, two options are distinguished: metabolic and toxicological. In the first case, endogenous ethanol is at the head - as a natural metabolite of metabolism. In the second, ethanol entering the body in excess acts as a powerful toxicological agent and a factor in metabolic disintegration of metabolism. Both in one and in the other case, practically the same systems work, metabolizing alcohol and aldehyde, and all the main systems of the body are involved in the metabolic processes of these compounds. Alcohol entering the body is oxidized by 75-95% in the liver. Other organs are significantly less able to metabolize ethanol. In addition, small amounts of it are excreted from the body with urine and exhaled air.

The main alcohol metabolizing systems:

Alcohol dehydrogenase (ADH, K.F.1.1.1.1) is an enzyme widely distributed in animal tissues and plants. ADH catalyzes the reversible conversion of alcohols to the corresponding aldehydes and ketones with NAD as a cofactor:

Alcohol + NAD □ aldehyde + NADH + H +

It should be emphasized that at physiological pH, the reduction of aldehydes or ketones proceeds tens of times faster than the oxidation of alcohol. Only with a multiple (100-1000 times) increase in the concentration of ethanol, as it happens when the body is loaded with alcohol, the enzyme functions in the opposite direction. Substrates for ADH are primary and secondary aliphatic alcohols and aldehydes, retinol, other polyene alcohols, diols, pantothenyl alcohol, steroids, □ -oxyfatty acids, 5-hydroxyethylthiazole and others. Moreover, it should be noted that ethanol and acetaldehyde are not the best substrates for ADH. The study of the intracellular distribution of ADH in the liver showed that the enzyme is localized in the cytosol of hepatocytes, but not in Kupffer's cells. The great functional value of ADH is confirmed by changes in the activity of the enzyme in organs and tissues under various pathological conditions. The natural function of ADH, which is present in large quantities in the liver of humans and animals, is that the enzyme forms, and does not consume, endogenous ethanol and, thus, actively regulates its level and provides homeostasis of endogenous acetaldehyde.

Microsomal ethanol-oxidizing system (MEOS). Ethanol oxidation by microsomes proceeds according to the following equation:

С2Н5ОН + NAPH + Н + + О 2 □ СН 3СНО + NADP + + 2Н О The optimum pH of this reaction lies in the physiological range, Km for ethanol is 7-10 Mm, which is much higher than for ADH. MEOS differs from ADH and catalase in sensitivity to inhibitors, as well as in a number of other properties. It is insensitive to the action of pyrazole and sodium azide. MEOS is activated by propylthiouracyl and thyroid hormones. It is believed that MEOS is identical with nonspecific oxidases that detoxify drugs in the liver, and that it is through MEOS that the ADH-independent pathway of ethanol oxidation in mammals passes through MEOS. MEOS, apparently, functions independently of ADH and catalase, and its contribution to the oxidation of ethanol is normally about 10%, but significantly increases with alcohol intoxication.

Catalase (K.F.1.11.1.6) in the presence of hydrogen peroxide is capable of oxidizing ethanol to acetaldehyde according to the equation:

С Ц ОН + Ц О2 □ СН3СНО + 2Н2О The enzyme functions in a wide range of animal tissues, and it has both species and individual fluctuations in its activity. Sources of hydrogen peroxide are reactions catalyzed by glucose oxidase, xanthine oxidase, and NADPH oxidase. The maximum activity of catalase appears at physiological pH. The rate of the catalase reaction depends on the concentration of ethanol and the rate of formation of hydrogen peroxide. The body has a significant number of systems that generate hydrogen peroxide and are localized in peroxisomes, endoplasmic reticulum, mitochondria, cytosol and create a concentration of hydrogen peroxide in the range of 10-8-10-6M. Like MEOS, the catalase pathway of ethanol oxidation is referred to as minor, acquiring a certain value only at high concentrations of ethanol in the body or under conditions of ADH inhibition.

The possibility of ethanol oxidation by converting its molecule into the □ -hydroxyethyl radical was shown, which can occur during the transfer of electrons by nitric oxide synthase, which is capable of forming a superoxide radical, as well as hydrogen peroxide. Researchers are of the opinion that nitric oxide synthase in terms of ethanol oxidation is no less significant than cytochrome P-450, provided that L-arginine is present as the main substrate.

One of the sources of endogenous ethanol in the animal body is the intestinal microflora. In experiments on angiostomized animals, by simultaneous sampling of blood from the portal vein and the peripheral venous bed, it was shown that the blood flowing from the intestine contains more ethanol than the blood flowing from the liver.

When assessing the balance relations in the metabolism of ethanol, therefore, one should reckon with two of its sources and the main, decisive role of hepatic alcohol-gold dehydrogenase in the regulation of the level of alcoholemia.

Oxidation of aldehydes in mammals occurs predominantly by nonspecific aldehyddehydrogenase (AldH, K.F.1.2.1.3). The enzyme catalyzed reaction is irreversible:

CH3CHO + NAD + + H2O □ CH 3COOH + NADH + 2H +

Liver aldehyde dehydrogenases are represented by two enzymes: with low (high Km) and high (low Km) affinity for acetaldehyde, preferably using aliphatic substrates and NAD as a coenzyme or aromatic aldehydes and NADP as a coenzyme. AldH exists in multiple molecular forms, differing in structure, catalytic characteristics, and subcellular localization. In mammals, AldH isoenzymes are classified into five different classes. Each class has a specific cellular localization that is predominant in different species, suggesting very early divergence in the evolution of AldH. In addition to dehydrogenase, AldH of the liver has esterase activity. AldH activity is found in mitochondria, microsomes, and cytosol.

Known, but less studied, and other enzymes involved in the transformation of acetaldehyde, such as aldehyde reductase, aldehyde oxidase and xanthinoxidase. But, as noted above, the reduction of acetaldehyde in the body is carried out mainly by AldH, and until now the only known precursor of endogenous ethanol is acetaldehyde.

For animal tissues, the following enzymes are known that take part in the production of acetaldehyde:

Pyruvate dehydrogenase (KF.1.2.4.1), usually catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA. In this case, the decarboxylating component of this polyenzyme complex is capable of releasing free acetaldehyde during the reaction. The latter is either oxidized by AldH in mitochondria to acetate, or in the cytoplasm, ADH is reduced to ethanol.

O-phosphorylethanolamine phospholyase (K.F.4.2.99.7)

An enzyme that breaks down phosphoethanolamine to acetaldehyde, ammonia and inorganic phosphate.

Threoninaldolase (K.F.4.1.2.5) - catalyzes the cleavage reaction of threonine to glycine and acetaldehyde.

Aldolase (K.F.4.1.2.7) of animal tissues has specificity only in the binding of dioxyacetone phosphate and uses any aldehydes as a second substrate. In turn, in the reverse reaction, acetaldehyde is formed in this way.

Recently, it has been shown that a decrease in the concentration of acetaldehyde in animal tissues under conditions of selective inhibition of the activity of pyruvate dehydrogenase can be counteracted by the inverse nature of changes in the activity of phosphoethanolamine lyase and threoninaldolase.

It is also known that during the decomposition of □ -alanine, a degradation product of pyrimidine nitrogenous bases, malonic aldehyde is formed first, and then acetaldehyde.

Concluding the analysis of literature data, it should be noted that endogenous ethanol is constantly present in the body of humans and animals in concentrations comparable to the levels of other natural inter-

diatoms of metabolism. The level of endogenous ethanol in blood and tissues is modulated by various compounds (hormones, vitamins, antimetabolites, amino acids and their derivatives, lithium salts, disulfiram, cyanamide) and changes under various functional states of the body (stress, starvation, aging), the mechanism of action of which is clearly not uniform. The very equilibrium in the endogenous ethanol / acetaldehyde system, provided by ADH and other enzymes that produce and consume acetaldehyde, obviously controls both the exchange of bicarbon and the synthesis of morphine-like compounds, and regulates the activity of some neurotransmitters, peptides, and proteins. In turn, changes in the activity of the alcohol- and aldehyde-metabolizing systems, both under their physiological and under conditions modified by alcoholic stress, are, in essence, adaptive, providing the appropriate functional and metabolic homeostasis.

The review is dedicated to the blessed memory of the teacher, Academician Yuri Mikhailovich Ostrovsky, who made a significant contribution to understanding the mechanisms of regulation of the metabolism of endogenous ethanol and acetaldehyde, their biomedical significance and the biochemistry of the development of alcoholic disease.

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