How many structures are there in cardiac glycosides? How to detect the difference

Structure and classification of cardiac glycosides.

1.Structure of the aglycone part: cardiac glycosides are formed by the condensation of cardiac aglycones and sugars. Naturally occurring cardiac glycosides are steroidal compounds with C17 side chains as unsaturated lactone rings. Its structural characteristics are as follows:

1) The fusing mode of the four rings of the steroidal parent nucleus a, b, c, and d is that there are two forms of a b ring, cis, and inverse, but most of them are cis; b c rings are trans; The C D ring is mostly cis.

2) The substituents of C10, Cl3 and Cl7 are all types. Cl0 is an oxygenated group such as a methyl group or aldehyde group, hydroxymethyl group, carboxyl group, C13 is a methyl group substitution, and Cl7 is an unsaturated lactone ring substitution. There are hydroxyl groups at C3 and Cl4 positions, and most of the C3 hydroxyl groups are configuration, and the sugars in cardiac glycosides are condensed with C3 hydroxyl groups to form glycosides.

The c14 hydroxyl group is the configuration.

3) According to the different cl7 unsaturated lactone rings, cardiac aglycones can be divided into two categories.

The CL7 side chain is a five-membered unsaturated lactone ring (lactones), which is called cardiac sterenes, that is, alpha-type cardiac glycosides. Among the known cardiac glycosides, most belong to this category.

The side chain of C17 is a six-membered unsaturated scorpion cholelide ring (lactones), which is called sium sterdienes or toad steryldienes, that is, beta-type cardiac glycosides. Only a few aglycones in nature belong to this category, such as the cardiac component toad poison ligand class in traditional Chinese medicine toad.

2.Structure of the sugar part: There are more than 20 types of sugars that make up cardiac glycosides.

According to the presence or absence of hydroxyl groups at the C2 position, they can be divided into two categories: -hydroxyl sugar (2-hydroxy sugar) and -deoxyl sugar (2-deoxy sugar). -Deoxytose is commonly found in cardiac glycosides and is an important feature that distinguishes it from other glycosides.

3.The way in which aglycones and sugars are attached.

Cardiac glycosides are mostly oligosaccharides, and a few are monoor or disaccharides. Generally, according to the type of sugar and the way it is connected to aglycone, it can be divided into the following three types:

Type: Aglycone-(2,6-deoxylux) x (D-glucose)Y, e.g. Digitalis A.

Type: Aglycone-(6-deoxylulose) x (d-glucose)y, e.g. xanthagoside A.

Type: Aglycone-(d-glucose)Y, such as green onionin.

Cardiac glycosides present in the plant kingdom are more and less type. A large number of studies have proved that the chemical structure of cardiac glycosides has a great influence on its physiological activity. The cardiotonic effect of cardiac glycosides depends on the aglycone part, mainly the three-dimensional structure of the steroidal parent nucleus, the type of unsaturated lactone ring and the types and configurations of some substituents.

The sugar fraction itself does not have a cardiotonic effect, but it can affect the cardiotonic effect of cardiac glycosides.

Mild acid hydrolysis and strong acid hydrolysis of cardiac glycosides and their respective characteristics:

Mild acid hydrolysis can hydrolyze cardiac glycosides into aglycones and sugars.

Strong acid hydrolysis and cardiac glycosides, because the sugar-hydroxyl group hinders the protonation of the glycosidic bond atoms, making hydrolysis more difficult, with mild acid hydrolysis can not make it hydrolyzed, must increase the concentration of acid, prolong the action time or at the same time pressurize.

Answer]: The color reaction of the unsaturated lactone ring at the CC17 position: In the alkaline alcohol solution, the double loss hail bond on the five-membered unsaturated lactone ring is shifted to produce C22 active methylene, which can react with the active methylene reagent and show the world's color.

In alkaline alcohol solution, beta-cardiac glycosides cannot produce active methylene groups, and there is no such reaction. Therefore, this type of reaction can be used to distinguish between type A and B cardiac glycosides. The kedde reaction belongs to this reaction and can be used to distinguish alpha-cardiac glycosides from beta-cardiac glycosides.

Hello, identification method: 1. For A-type cardiac glycoside and B-type cardiac glycoside, because A-type cardiac glycoside can be translocated in alkaline solution to form active methylene group, it is enough to add active methylene chromogenic reagent, and m-dinitrobenzene or picric acid can be used.

2. For rutin and quercetin, because rutin contains a glycoside structure, 10%-naphthol ethanol solution can be added and concentrated H2SO4 can be added along the wall for identification, and rutin can be positive in the Molich reaction

3. For triterpene saponins and steroidal saponins, acetic anhydride-sulfuric acid recognition reaction can be carried out, and triterpene saponins appear red at the end, and steroidal saponins appear green at the end