GLYCOSIDES

From Big Medical Encyclopedia

GLYCOSIDES (heterosites) eurysynusic in the nature, especially in flora, substances in which molecules the remains of sugars (the glikozilny remains) are connected through oxygen atom, sulfurs or nitrogen with a molecule of the substance which is not sugar and called aglikony. Respectively distinguish O-(I), S-(II) and N-(III) glycosides. The term «C-glycosides» designate connections in which the glikozilny rest is connected directly with atom of an aglikon (IV):

Many medicinal substances, including having selective effect on a cardiac muscle belong to G. The greatest value and distribution in the nature have About - and N-glycosides.

Are divided into pyranosides and furanozida depending on presence of six - or pentatomic ring in the rest of sugar (see. Monosaccharides ), and also on alpha glycosides and beta glycosides depending on alpha and beta configurations of the C-atom connected through oxygen with an aglikonovy part of a molecule.

O-glycosides

O-glycosides can be considered as derivatives of sugars in which hemiacetal hydroxyl hydrogen atom is replaced by the radical aliphatic, carbocyclic or heterocyclic compound. Though in many O-glycosides a glyconew part of a molecule are the remains of simple sugars, however the remains of oligosaccharides (di - three - etc. saccharites) can be it also. The O-glycosides which are found in the nature in most cases are beta glycosides. At last, depending on the nature sugar components distinguish pentozida (O-glycosides of pentoses), napr, ksilozida (O-glycosides of xylose), arabinozida (O-glycosides of pectine sugar), etc.; geksozida (O-glycosides of hexoses), napr, glucosides (derivative glucose), galactosides (derivative galactoses), fruktozida, and also biosides (O-glycosides bioz — disaccharides), napr, maltozida, laktozida etc. As glycosides are constructed oligosaccharides (see) and the highest polysaccharides (see).

On character of an aglikon O-glycosides divide into a number of groups, including into cerebrosides (see) — galactosides of sphingosine; steroid O-glycosides, napr, cardiac glycosides (see), saponins (see), etc.; nitrogen-containing O-glycosides, napr, dl-mandelonitrile gentiobioside, indican; glycoalkaloids, connections, in which sugar a component it is connected by an O-glycosidic linkage to the rest of alkaloid (solanine, demissin), etc.

O-glycosides can be received synthetic or allocated from natural sources. So, alkylglycosides receive at interaction of sugar a lot of alcohol in the presence of catalystically the operating dry hydrogen chloride or enzymes alpha and beta glucosidases. It is economic to allocate many natural O-glycosides of complex structure (flavonglikozida, steroid glycosides, etc.) from natural sources. Biosynthesis of O-glycosides in plants happens preferential by transfer of the glikozilny rest from a nukleoziddifosfatsakhar on phenol or alcohol, napr, an uridindifosfatglyukoza + hydrochinone —> uridinephosphate + hydrochinone - beta D - glucoside (ursin).

O-glycosides represent the solid crystal matters most often having various specific taste. The vast majority of O-glycosides is not hydrolyzed by alkalis; the exception is made only by some G. which aglikonam are the phenols, enols and alcohols containing negatively charged groups in β-situation (e.g., WITH; NO 2 ). O-glycosides usually have no reducing power, except for G. sensitive to alkalis, and also those G., aglikona which have the recovering properties.

Are hydrolyzed to-tami, and furanozida girolizutsya many times quicker than pyranosides. Character of an aglikon, and also a configuration of all asymmetric atoms of the rest of sugar exert impact on the speed of hydrolysis, alpha and beta glycosides are hydrolyzed by specific enzymes - alpha and beta glucosidases (see. Glucosidases ).

Many O-glycosides find application In medicine as valuable pharmaceuticals, (see below); some have toksikol. value (saponins, solanine) or are applied as vitamins (Rutinum — vitamin P).

S-glycosides

S-glycosides (thioglycosides) represent derivatives of the cyclic I-tiosakharidov forms, in mercaptogroup (— SH) which hydrogen atom is replaced by the radical.

S-glycosides can be received interaction of acetates of glikozilbromid with benzenethiols in the presence of alkali with the subsequent saponification of acetyl groups of the formed S-glikozidyaogo acetyl of derivative. S-glycosides are very resistant in relation to acid hydrolysis, but Strong caustics split them with formation of thiosugars.

The major natural S-glycoside is G. of black mustard — the sinigrin which is split enzyme thioglucosidase (mirozinazy, sinigrinazy; To F 3.2.3.1) with formation of allylic mustard oil; it is known the St. 40 natural S-glycosides close to sinigrin.

N-glycosides

N-glycosides (secondary or tertiary glikozilamina) are considered as derivatives of glycozymin (primary glikozilamin); they are formed as a result of substitution of one or two hydrogen atoms in an amino group by the remains of connections of an aliphatic or heterocyclic series.

As well as O-glycosides, N-glycosides can be constructed as pyranosides or furanozida and to have alpha (I) and a beta form (II). Unlike O-glycosides, N-glycosides in solutions can partially be in a type of the acyclic tautomeric forms (like Schiff bases) which are intermediate (III):

For the first time crystal N-glycosides were received by interaction of aniline and sugars, many N-glycosides receive direct interaction of sugar and amine in the cold or during the heating in a spirit, alcohol-water or aqueous medium, in absence or in the presence of catalysts — acetic or salt to - you, ammonium muriate etc.

Properties of N-glycosides depend substantially by nature aglikon. Alkyl - and aryl - N-glycosides (e.g., purine - and pyrimidines-N-glycosides) are steady against action to - t and alkalis.

Extremely important cleavage products in a metabolism nucleinic to - t and nucleoproteids (nucleotides and nucleosides), some the major belong to N-glycosides coenzymes (see), adenosine triphosphoric acid (see), uridinetriphosphate, nicotinamide adenine dinucleotide, nikotinimidadenindinukleotidfosfat (NAD and NADF), some antibiotics, etc.

N-glycosides of sulphonamide drugs are artificially synthesized: «glucostreptocide», N-glucoside of Sulfidinum, norsulfazolglyukozid, different from initial aglikon much bigger solubility, smaller toxicity and sometimes modified nature of action.

N-glycosides of aliphatic amines with a long chain (dodecyl - and octadecylamines) are applied in the textile industry.

N-glycosides of some arylamines are offered as antioxidants of rubber.

S-glycosides

C-glycosides meet in the nature (bergenin, psevdouritin) and can be received synthetic; differ from all other groups G. in inability to hydrolysis.

Medicinal glycosides

Medicinal glycosides are not uniform pharmakol, group: the range of their action is very wide that is caused by a structure of both an aglikon, and a glyconew part of their molecule. A glyconew part strengthens and accelerates action of an aglikon, increases its solubility, promotes its best penetration into cells of an organism, gives stability to a molecule G. and causes the corresponding feature of action.

From an extensive class of O-glycosides steroid G., and first of all the derivatives of cyclopentaperhydrophenanthrene relating to group have the greatest value cardiac glycosides (see). Other steroid G. apply to treatment of atherosclerosis (Diosponinum, etc.), diseases of veins (astsin, esflazid, etc.). Drugs G. antiinflammatory, hormonal, neurotropic, tonic and gonadotropic action are received (aralozida, AVS-saporal, panaksozida from a root of a ginseng, etc.). Among O-glycosides it should be noted also drugs of laxative and diuretic action, and also bioflavonoids (see).

G. of coumarins and chromones are applied to treatment of some diseases of vessels (esculin, kellozid).

Medicinal G.' number has an antimicrobic, anti-virus and cytopathic effect. Some antibiotics received from Strep tomyces belong to such G. (see. Streptomycin ) and other sources, dl-mandelonitrile gentiobioside, etc. There are data that the synthetic N-glycosides having as a glyconew part or in its structure a ribose and desoxyribose possess a wide range of medicinal action and are applied as stimulators of a metabolism, immunodepressants (see. Immunodepressive substances ), chemotherapeutic means, etc.

also S-glycosides contain in a number of plants (mustard, a spring adonis, a hawthorn, etc.). Many medicinal G. have bitter taste therefore plants, them containing (a centaury, a wormwood, etc.), use in quality [[ | is hotter than BITTERNESS ]] (see).

Medicinal G. in most cases belong to strong drugs and are applied in small doses.

Glycosides in the medicolegal relation

G.'s Identification is of great importance at accidental poisonings.

Most often the most toxic appear cordial G. Intoksikation can develop even at use of therapeutic doses. At court. - medical establishment of poisonings of G. features a wedge, pictures are of great importance: strong weakness, spasms, coma, bradycardia; disturbance of conductivity and emergence of initiation of cordial activity that can cause a tachyarrhythmia of ventricles of heart. Complete cessation of cordial activity can preferential come in a stage of a diastole. At G.'s poisonings dysfunctions of c can be observed. the N of page also went. - kish. path, and also oliguria. At a research of a corpse specific changes of bodies do not find, sometimes note a nek-swarm their plethora.

Data court are of great importance for the proof of fatal poisonings of G. - chemical researches of cadaveric material, and also the remains of the drugs which served presumably as a cause of death.

From a human body are allocated preferential with bile and partially with urine. For court. - chemical examinations special value has a research of bile and a gall bladder, and also the sites of a liver adjacent to a gall bladder and fabrics from the place of injections.

G.'s keeping in cadaveric material during 1 year is reached by conservation by ethanol, a cut shall be made directly after capture of objects of a research.

Scheme judicial chemical definitions of. includes several main stages: extraction of cadaveric material of 70% ethanol at pH 7,0; sedimentation in extract of proteins; cleaning with extraction with perchloromethane; extraction of Oleandrinum and lanatosidums hloroformnospirtovy mix 9:1 (t, to. strophanthin is strongly hydrophilic connection, in these conditions it is not taken); cleaning of the taken fraction of Oleandrinum and lanatosidums of the accompanying substances with alkali; qualitative and quantitative definition and so forth; extraction of strophanthin alcohol-chloroformic mix (8:2); sedimentation of strophanthin from an aqueous phase ammonium sulfate at full saturation, dissolution of a deposit, reprecipitation and extraction of strophanthin with its subsequent qualitative and quantitative definition.

High-quality detection of strophanthin is made by method of paper chromatography, Oleandrinum and lanatosidums — method thin layer chromatography (see). Spots of strophanthin are specifically shown 3,5-dinitrobenzoic to - that, meta-dinitrobenzene and 2,4-dinitrodifenilsulfony; Oleandrinum is shown except the specified reagents, the concentrated chamois to - that, containing traces of iron.

Quantitative definition of G. in eluates is made, generally by a fotokolorimetrirovaniye of the painted solutions after reaction with 2,4-dinitrodifenilsulfony in alkaline condition.

The described scheme of a research allows to open 30 — 50 mkg of G. on 100 g of wet weight of fabric.


Bibliography: Vlasenko L. M. To a question of systematic judicial and chemical definition of cardiac glycosides, in book: Vopr. court. medical, under the editorship of V. I. Prozorovsky, page 233, M., 1971; Votchalb. E. and With lutskiym. K. Cardiac glycosides, M., 1973; Kochetkov N. K., etc. Chemistry of carbohydrates, M., 1967; Savitsky H. N. Pharmakodinamika of cardiac glycosides. L., 1974, bibliogr.; Stepanenko B. N. Carbohydrates, Progress in studying of a structure and metabolism, M., 1968.

B. N. Stepanenko; Ya. I. Hadzhay (pharm.), A. F. Rubtsov (court.).

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