Page 163 - phytochemistry I - PharmD Clinical

- Legal’s test: Cardenolide in pyridine + Na nitroprusside + NaOH→deep
red color.

- Color reactions due to the 2-deoxy sugar moiety:
1. Keller-Killiani’s test: Add glacial acetic acid and a few drops of 5%
ferric chloride solution to the drug extract. Further add concentrated
sulfuric acid. The result is the formation of blue color in acetic acid
layer.

Saponins

Saponins are glucosides with foaming characteristics and widely
distributed in the higher plants. Saponins consist of a polycyclic aglycones
attached to one or more sugar side chains.

The aglycone part, which is also called sapogenin, is either steroid (C27)
or a triterpene (C30).

They are readily soluble in water, and have the ability to form lasting foam
when shaken in aqueous solutions, i.e., they modify surface tension. The
surface-activity of saponins is caused by the combination of a
hydrophobic (fat-soluble) sapogenin and a hydrophilic (water-soluble)
sugar part.

Physical properties:

1. Pure saponins are usually colorless or white and optically active.
2. They form colloidal solutions with water, soluble in alcohol and

dilute alcohols.
3. Saponins have a bitter taste.
4. The stability and strength of forage saponin foams are affected by

pH.
5. Saponins are remarkably stable to heat processing, and their

biological activity is not reduced by normal cooking.
6. Saponins have haemolytic properties, as they precipitate the

cholesterol and/or the lecithin that exist in the membranes of the

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