Cardiac Glycosides

Thecardiac glycosides are basically steroids with an inherent ability to afford a very specific and powerful action mainly on the cardiac muscle when administered through injection into man or animal.

Small amount would exhibit a much needed stimulation on a diseased heart, whereas an excessive dose may cause even death.

Lactones ring is very important for therapeutic activity.

Removal of lactone ring or even a slight disturbance to the lactone ring means that the activity of the activity is lost.

Cardiac glycosides contain a special sugar called digitoxose; through they do carry other sugar like glucose and rhamnose.

Very often diuretic action is also associated with steroidal glycosides as they also promote improved circulation of blood through kidneys.

Classification of cardiac glycosides

Cardenolides:

They are C23 steroids that have a 17-β side chain and α, unsaturated β-membered lactone ring.

Example:

Digitalis, Quabain, Strophanthin, etc

Bufadienolide:

Thebufadienolides are C24 homologues of the cardenolides and carry a doubly unsaturated 6- membered lactone ring at the 17-position.

The bufadienolides derived their name from the genetic name for thetoad, Bufo (the prototype compound bufalin was isolated from the skin of toads).

Example:

Squill, etc

Chemical tests for cardiac glycosides:

1. Raymond’s test:

Tothe drug, add a few ml of 50% ethanoland 0.1 ml of 1 % solution of m- dinitrobenzene in ethanol.

To this solution, add 2-3 drops of 20% sodium hydroxide solution. Violet colors appears, this is due to presence of active methylene group.

2. Legal test:

Tothe drug, add few ml of pyridine and 2drops of nitroprusside and a drop of 20% sodium hydroxide solution. A deep red colour is produced.

3. Killer killiani test:

Glycoside is dissolved in a mixture of 1 % ferric sulphate solution in (5%) glacial acetic acid. Addone or two drop of concentrated sulphuric acid. A blue colour develops due to the presence of deoxy sugar.