5. Glycosides and cardiac glycosides

Question 1

What are glycosides?

Answer 1

Glycosides are compounds that yield one or more sugars among the products of hydrolysis.

Question 2

What are the most frequently occurring components of glycosides?

Answer 2

The most frequently occurring sugar is beta-D-glucose, although rhamnose, digitoxose, cymarose, and other sugars are components of glycosides

Question 3

What are the components of glycoside?

Answer 3

It consists of two components the sugar component which is known as glycone and a non-sugar component which is aglycone or genin.

Question 4

What is the biosynthesis of glycosides?

Answer 4

The principal pathway of glycoside formation involves the transfer of a uridylyl group from uridine triphosphate to a sugar 1-phosphate. Enzymes catalyzing this reaction are referred to as uridy lyl transferases (1) and have been isolated rom animal, plant, and microbial sources.. The subsequent reaction, mediated by glycosyltransferases (2), involves the transfer of the sugar from uridine diphosphate to a suitable acceptor (aglycone), thus forming the glycoside.

Question 5

Give the extraction of glycosides?

Answer 5

The method by which glycosides are isolated is known as stas-otto method. In this a finely powdered sample is taken and then it is extracted with alcohol or water. After extraction collect the extract and treat with lead acetate to precipitate tannins after that filter it and to the filtrate pass H2S gas to precipitate the lead acetate. Again filter the extract. The filtrate is subjected to various techniques which gives pure component.

Question 6

On which bases are glycosides classified?

Answer 6

They are classified on many basis but mostly on the basis of aglycone groups

Question 7

Which groups are glycosides classified into?

Answer 7

1. Cardiac Glycosides or sterols: eg:digitalis
2. Anthraquinone Glycosides:Eg:Senna
3. Saponin Glycosides Eg:Liquorice
4. Cyanophore Glycosides Eg:White cherry
5. Isothiocyanate Glycosides Eg:Black Mustard
6. Flavonoid Glycosides Eg: Citrus
7. Biofalvonoids
8. Aldehyde Glycosides Eg:Vanilla pods
9. Phenol Glycosides Eg: Uva ursi or bearberry
10. Lactone Glycosides Eg: Coumarin

Question 7

What are cardiac glycosides?

Answer 7

These are an important class of naturally ocuring compounds found in certain plants like foxglove with specific action on heart.

Question 8

Why are they called as cardiotonics?

Answer 8

They are also referred as cardiotonics i.e. they strengthens the muscles of heart by increasing the force of contraction of the heart, making the heart more effective in pumping blood.

Question 9

What is the use of cardiac glycosides in modern medicine?

Answer 9

They are used in modern medicine to treat various conditions like cardiac arrythmias and heart failure.

Question 10

What are the types of cardiac glycosides?

Answer 10

On the basis of steroidal aglycone part there are two types:
1. Cardenolides: they are C 23 steroids that have an unsaturated 5 membered lactone ring at carbon 17 position.(Digitoxigenin, Digoxigenin)
2. Bufdienolides: they are 24-carbon steroids with a double unsaturated six-membered lactone ring on carbon 17.(Scillarenin)

Question 11

What are some examples of cardiac glycosides?

Answer 11

Following are some examples of cardiac glycosides:
1.Digitalis
2.Strophanthus
3.White Squill

Question 12

What is digitalis?

Answer 12

Digitalis or foxglove is the dried leaf of Digitalis purpurea.

Question 13

What is the family of digitalis?

Answer 13

Scrophulariaceae

Question 14

What are the constituents of digitalis?

Answer 14

The drug contains a large number of glycosides of which the most important from a medicinal viewpoint are digitoxin, gitoxin, and gitaloxin. The total concentration of these 3 glycosides varies appreciably with the plant source and the conditions of growth.

Question 15

What is the dose for digitalis?

Answer 15

The usual dose of digitalis is 100 to 200 mg daily in the form of tablets or capsules .

Dose must be reduced by 25 to 30% for the elderly, for patients with lean body mass, and for patients with metabolic or electrolyte disorders.

Question 16

What are the uses of digitalis?

Answer 16

Digitalis is used in the form of tablets or capsules to treat congestive heart failure, paroxysmal atrial tachycardia, atrial flutter, ad atrial fibrillation.

Question 17

What is strophanthus?

Answer 17

Strophanthus is the dried, ripe seed of Strophanthus kombe, or of S. hispidus that is deprived of the awns.

Question 18

What is the family of strophanthus?

Answer 18

Apocynaceae

Question 19

What are the constituents of strophanthus?

Answer 19

K-strophanthoside also known as strophoside, is the principal primary glycoside in both S. kombe and S. hispidus. It is composed of the genin, strophanthidin coupled to a trisaccharide consisting of cymarose, beta-glucose, and alpha-glucose.

Question 20

What is Ouabain?

Answer 20

Ouabain is a glycoside obtained from the seeds of Strophanthus gratus. It is extremely poisonous. Ouabain is also known as G-strophanthin.

Question 21

What is white squill?

Answer 21

Squill or squill bulb consists of the cut and dried, fleshy, inner scales of the bulb of the white variety of Urginea maritima known in commerce as white or Mediterranean squill.

Question 22

What is the family of white squill?

Answer 22

Liliacea

Question 23

What are the constituents of white squill?

Answer 23

Squill contains about a dozen cardioactive glycosides. The principal one, scillaren A, comprises about two thirds of the total glycoside fraction. On hydrolysis. it yields the aglycone scillarenin, a bufadienolide, plus rhamnose and glucose. Other minor glycosides include glucoscillaren A (scillarenin + rhamnose - glucose + glucose) and proscillaridin A (scillarenin + rharnnose).

Question 24

What are the uses of white squill?

Answer 24

Squill is an expectorant, but it also possesses emetic, cardiotonic, and diuretic properties.