• These are medicinally and commercially important.

• Soap like action shown by the aglycone part of these glycosides.

• They exhibit some physical properties like foaming action by shaking with water and yielding colloidal solutions.

• They cause haemolysis of erythrocytes because of this they are generally considered as haemotoxic.

• Due to this activity, some of them are used as fish poisons.

• Saponins have a bitter and acrid taste.

• They cause irritation of mucous membrane.

• They are mostly non-crystalline substances soluble in water and alcohol; but insoluble in non-polar organic solvent Chemically

• They contain aglycone called as sapogenin.

• Sapogenins are high molecular weight substances which by acetylation give crystalline forms.

• The harmful sapogenins are called as sapotoxins.

• Depending on the nature of aglycone, saponins are categorized into 2 groups viz.

  • • • (i) Steroidal saponins (Tetracyclic triterpenoid saponins)

      • (ii) Pentacyclic triterpenoid saponins Both types of aglycones are linked with different types of sugars and uronic acids .

• Steroidal saponins are used as raw material for the synthesis of various medicinally useful steroids

• Like vitamin D, cardiac glycosides, corticoids like betamethasone and cortisone acetate, sex hormones like progesterone, testosterone and oestradiol, oral contraceptives such as mestranol and norethisterone; and spironolactone which is a diuretic steroid, Steroidal sapogenins viz. diosgenin and hecogenin can be considered as a representative example of this group of saponins.

• Due to their pharmaceutical importance, many plants have been screened for the detection of steroidal saponins.

• Their distribution is limited to plant kingdom, In dicot plants, important sources are from Leguminosae, Solanaceae, Apocynaceae, etc.

• They are mainly obtained from monocot plants like Liliaceae, Dioscoreaceae and Amaryllidaceae.

• Besides the chemical structure, these types of saponins differ from steroidal saponins by way of their distribution.

• Pentacyclic triterpenoid saponins are available from various families of dicot plants like Polygalaceae, Caryophyllaceae, Berberidaceae, Umbelliferae, Rubiaceae, Compositae, Primulaceae, Rutaceae, Chenopodiaceae, etc.

• They are however scarcely found in monocot plants.

References:

1. Trease D. & Evans W.C.: Text Book of Pharmacognosy: W.B. Saunders.

2. Tyler V. E. Brady L. R. & Robbers J. E.: Pharmacognosy; Lea Feibger, USA.

3. Wallis T. E.; Text Book of Pharmacognosy; CBS Publishers, Delhi.

4. Kokate C. K., Purohit A. P. & Gokhale S. B.: Pharmacognosy; Nirali Publications, Pune.

5. Harbone J. B.: Phytochemical Methods: A guide to modern techniques Analysis: Chapman & Hall, London.

6. Bruneton J.: Pharmacognosy, Phytochemistry, Medicinal Plants: Intercept Limited.