Page 49 - Phytochemistry -1 (PG404) / Clinical Pharmacy 2nd level students ( 2019 )

Clinical pharmacy PharmD program Third level Phytochemistry-1 (PG-504)

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QUANTITATIVE DETERMINATION OF SOME
GROUPS OF GLYCOSIDES
Anthraquine glycosides
Assay of Sennosides e.g. Assay of Senna Tablets

(Senna lax.)
Principle of Assay:
The method depends on the fact that senna contains mainly combined

anthraquinones (Sennosides) with a small amount of free anthraquinones.
Since senna is assayed for its content of sennosides, removal of free
anthraquinones should be done first by extract with organic solvent. The

sennosides are then dissolved in 5% Na 2CO 3 solution. Oxidative cleavage
at the C 10-C 10 bond by heating with FeCL 3 at pH 7-8, give
dihydroxyanthraquinone-3-carboxylic acid-8-giucoside (rhein-8-

glucoside). After the addition of HCL, reflux to ensure hydrolysis of the
glycoside into free rhein which is extracted by the organic solvent (e.a:
ether). Addition of standard alkali e.g. 1N KOH to the residue after
evaporation of ether gives a rose red color, (Borntrager's test) which is

measured calorimetrically at 500 nrn, using a suitable, colorimeter. The
intensity of the color produced is proportional to the concentration of

sennosides. Using a standard curve of E 1%, the percentage of the total
combined anthraquinones in senna can be determined.

Procedure:

1- Triturate 2 tablets (e.g. senna lax) in a mortar with 20 ml of distilled
water, then transfer the mixture quantitatively (using 20 ml of dist.
water) into a conical flask.

2- Digest the mixture on a boiling water bath for 15 minutes and filter
while hot into a 250 ml separating funnel. Wash the flask with 20 ml
distilled water, add the washings to the separator.

3- Cool the mixture, add 2 drops HCL, and shake gently the mixture, add
2 drops HCL, and shake gently with two portions each of 15 ml
CHCL 3. Discard the CHCL 3 layer.

.
4- Filter the aqueous layer through a piece of cotton into a. 100 ml
volumetric flask. Complete with water to the mark.
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