General Chemical tests for the presence of Glycosides in Crude Drugs


TEST-1
•First the drug is extracted.
•200mg of the drug is warmed in a test tube with 5ml of dil. Sulphuric acid(10%),othe water bath at 100°C for 2 min. & then filter it.
•The acid extractis neutralized by adding 5% solution of Sodium Hydroxide.
•Then add 0.1 ml of Fehling's solution A & then Fehling's solution B until alkaline (test with pH paper)& heat on the water bath for 2 min.
•Note the quantity of red precipitate formed.
TEST-2:-
•200mg of drug is treated with 5 ml of water instead of sulphuric acid.
•After boiling, add a volume of water equivalent to the volume of sodium hydroxide used in test 1.
•Add 0.1 ml of Fehling's solution A and then Fehling's solution B until alkaline and Heat on the water bath for 2 minutes.
•Note the quantity of red precipitate formed.
COMPARISON BETWEEN TEST-1 &TEST-2
Compare the quantity of red precipitate formed in test 2 with that formed in test 1.
•If the intensity of red precipitate is same in both the cases then glycoside is absent.
•If intensity is different, it is concluded that glycoside is present.For example if the precipitate in test 1 is greater than that in test 2, then the glycoside may present.
N.B.
Reduced sugar in free form react with glycosides.
•Test-1: Free reducing sugar +related acid hydrolysis products.
•Test-2: Only free reducing sugar present.
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