Glycosides – Chemical Tests and Isolation

Chemical Tests For Cardiac
Glycosides:

S.No

Test

Observation

Inferences

1

KellarKilliani
Test:

 

The glycosides dissolved in glacial acetic acid
containing a traces of FeCl3, add the same amount of FeCl3 dissolved in conc. H2SO4 along the side of
the test tube.

A reddish brown colour changing to

 

bluish green colour appear at the
junction of two reagents within 25 mins spreading slowly into the acetic acid layer.

For αdeoxy sugars

 

(Digitoxose)

2

Legal test:

 

Few mg of the glycosides (Scillaren)

 

Is dissolved in a
few drops of pyridine. To this add
a drop of sodium nitroprusside solution (2%) and a
drop of NaOH (20%)

Appearance of pink or deep red

 

colour

Cardiac Glycosides

 

present

3.

Baljet test:

 

The aglycone portion of the glycosides is mixed
with Baljet reagents.

[Baljet reagents: Aqu. Solution of picric acid (1%)
and NaOH (10%), both are mixed immediately before used]

Appearance of Yellow to orange

 

colour

Cardiac Glycosides

 

present

4

Kedde test:

 

A solution of glycosides is treated
with small
amount of Kedde reagents

[Kedde reagents: Mix
equal volume of a
2

solution of 35dinitrobenzoic acid in methanol

 

and 7.5% aqu. Solution of KOH]

Development of blue or violet

 

colour, which fades out in 12
hours.

Cardenolides

 

and

 

Bufadienolides

Isolation of glycosides

The dried plant material is rendered into a moderately coarse powder. 

The powder is  then extracted in a Soxhlet apparatus with aqueous ethanol. 

The non-glycosidal impurities which get extracted along with glycosides are removed by precipitating them with lead acetate solution. 

The excess of lead acetate is then removed by passing hydrogen sulphide gas through the extract. 

Lead gets precipitated as lead sulphide, which is filtered out.

The filtrate contains the glycosides. 

The glycoside can be obtained by removal of the solvent under reduced pressure or any other suitable procedure. 

Further purification of the isolated glycosides is done by column chromatography.

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