Pharmacognosy - medicinal plants (herbs)
Pharmacognosy - medicinal plants (herbs)

Theme X: Glycosides

Saponins

Saponins. Definition, characteristics and properties. Digitonin structure.

What are saponins?

Saponins are a group of oily glycosides, which are water soluble, they foaming when the solutions are agitated.

 

They are contained in variety of plants, including the thistle, the saponaria, horse chestnut and many others.

 

These active ingredients are related to plant sterols, its main feature is to contain many hydroxyl groups and linkages of ether and lactonic type.

 

They are plant secondary metabolites which are of pharmacological interest for its therapeutic actions.

Digitonin Saponin
Digitonin

The digitonin in the digitalis seeds is a typical saponin. With cholesterol (one 3β - hydroxysteroid) forms an addition compound with very low solubility which can be attributed their hemolytic inhibition action. The digitonin is a glycoside formed by a pentasaccharide and digitogenin steroid.

Characteristics and properties of saponins

Saponins are excellent emulsifying agents and some of them were used as detergent in place of soap, especially, as foaming, mainly in fire extinguishing liquids.

 

They have pungent flavor and the powder form may produce sneezing, are almost free of oral toxicity.

 

Some saponins are remarkably toxic. These are called sapotoxins and have a hemolytic action over red blood cells if are injected directly into a vein.

 

Most have to the general formula CnH2n-8O10.

 

Aglycones, usually prepared by acid catalyzed hydrolysis, have a sapogenin and usually a sugar is glucose.

 

Two general types are known: steroids such as digitonin and triterpenoid as aesculin (present in the seeds of chestnuts).

 

The research aimed to understand the precursors of cortisone resulted in the discovery of the presence of saponin in plants.

 

It seems clear that steroids derived in cortisone are: diosgenin and the botogenin from genus dioscorea; hecogenin, manogenin and gitonenin from the Agave species.

 

Saponins are widely scattered in the plant kingdom. Commercial saponin is prepared from the cassava plant (Yucca) or Quillaja or Quillay (Quillaja saponin). Some saponins are used in the synthesis of steroid hormones.

Plants that contain saponins should be used under medical supervision because of the risk of poisoning.

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Saponins. Definition, characteristics and properties. Digitonin structure.