LAB REPORT
Alkafeel University/Pharmacy Department
Name: Mohannad Fadhal
Lab Name: Pharmacognosy
Date: 11/11/2018
Group: B1
Title Anthraquinone Glycosides’ Chemical Test
Abstract
In this experiment, we will evaluate the compound that we extracted from
the previous experiment, and make sure that what we extracted is indeed
what we want through the usage of the general and specific tests that are in
experiment. Then after taking the result from the general and specific test,
we will now analyze the compound using TLC, and compare the Rf value
between the standard sample and our compound to get what the TLC is
generally capable of doing, which is identification and impurities checking.
Introduction
The anthraquinone glycosides are the ones whose aglycone component is a
polyhydroxyanthraquinone derivative. The drugs having these glycosides possess cathartic
activity. The polyhydroxyanthraquinone derivatives present in these drugs are chrysophanic
acid (1, 8- dihydroxy- 3- methylanthraquinone), aloe emodin (1, 8- dihydroxy-3- methyl
anthraquinone), Frangula emodin and rhein (1, 8- dihydroxy anthraquinone -3-carboxylic
acid).
Glycosides of anthranol and anthrones, reduced derivatives of anthraquinones, also occurs
in the plant materials, and they make significant contributions to the therapeutic action of
these natural products. The free anthraquinone aglycones exhibit little therapeutic activity.
The sugar residue facilitates absorption and translocation of the aglycone to the site of
action. The anthraquinone and related glycosides are stimulant cathartics and exert their
action by increasing the tone of the smooth muscle in wall of the large intestine.
Glycosides of anthranol and anthrones elicit a more drastic action than the corresponding
anthraquinone glycosides and a preponderance of the former constituents in the glycosidic
mixture can cause discomforting griping action.
LAB REPORT
Alkafeel University/Pharmacy Department
Procedure
General test reactions procedures:
1- Schonteten’s Reaction (Borax test):
To 2ml of the Senna extract, add 0.1gm of Borax and heat until dissolved.
Pour a few drops of the liquid into test tube nearly full of water.
2- Bromine Test:
Take 2ml of the Senna extract, add an equal volume or an excess of freshly
prepared solution of bromine. Record the color.
Specific test reaction procedure:
 Borntrager's test:
Take 1 ml the fraction B (free aglycone) and shake it with 2 ml dilute
ammonia (10%). Check the intensity of the color.
Chromatography test procedure:
1) Prepare 100ml of mobile phase, and place it in the glass tank.
2) Cover the tank with glass lid and allow standing for 45 minutes before use.
3) Apply the sample spots (fraction A, fraction B& fraction C), and the standard
spot on the silica gel plates, on the base line.
4) Put the silica gel plate in the glass tank and allow the mobile phase to rise
to about two-third of the plate.
5) Remove the plate from the tank, and allow drying at room temperature,
spray first with 25%nitric acid solution and heat for 10 minutes at 110 0C.
6) Allow to cool, and then spray with 5% w/v alcoholic KOH solution. Detect
the spot formed and calculate the Rf values.
Results
1.
2.
3.
4.
Shonteten’s reaction  light green color
Bromine test  clear but turbid solution
Borntrager’s test  light pink color
TLC  Rf are nearly matching together with tailing, which proves the
existence of impurities
LAB REPORT
Alkafeel University/Pharmacy Department
Discussion
In this lab, we will be doing three tests; the first is general, and it is used to
prove the existence of glycoside only without specifying the type. The
second is specific, and it will help us identify what kind of glycosides we
have. The third is TLC, and it will help with both identification and
impurities checking.
The first test, Shonteten’s test, will be use, and it includes the addition of 1
ml of senna 0.1 g of borax. The benefit of borax here is its usage to make a
complex with sugar, which can be benefited from to identify the existence
of the glycone part of a glycoside, and if the test gives a positive result the
color will change to light green. In the first test, we will be using water bath
because the reaction with borax is slow, which will increase borax solubility
and hastens the formation of the complex. This general test may give a false
positive result because borax react with sugar in general despite it is part of
a glycoside or free sugar. So, if we don’t have a previous idea about what
type of compound we are testing for; anything with sugar, even pure sugar
will be suspected. After the reaction finishes, we will need to add few drops
of the complex to a water-containing test tube. We use the water here to
dilute the complex because the senna glycoside’s brown color is shadowing
the light green color of the complex. So, by diluting the color of the complex
will appear proving the existence of a glycone part.
The second test will use bromine as an oxidizing agent that helps in also
identifying the existence of a glycone part in our glycoside through reacting
with it. The reaction positive result will appear as a clear solution that
contains turbidity. When we use bromine, we must take our precautions by
wearing the labs gadgets (gloves & facemask) because bromine is a
dangerous material that even one drop of it could cause a burn.
The third test will be done after the first and second tests, and that is after
proving the existence of the glycone part of the glycoside. This test,
Borntarger’s test, will allow us to prove what kind of glycoside we have in
our hands. It includes the addition of ammonia to the aqueous layer
portion of the sample which contains the aglycone dianthrone. The color
that we will get will be light pink color while if we had monoanthrone, we
would get dark pink color. The reason as to why we have dianthrone in the
aqueous portion of the previous experiment sample when we should have
LAB REPORT
Alkafeel University/Pharmacy Department
monoanthrones is because dianthrones bounds from the previous
experiment didn’t break to form monoanthrones. This happened because
we didn't finish the experiment until the end by heating it to about 20 min
in order to break the bounds by generating enough activation energy. The
compound that will be formed by the color change is a gel-like salt that will
precipitate and take the lower layer of the test tube.
After we have finished with all the tests; now, we will start running the
TLC test. In this test, we will compare between the Rf value of a standard
senna glycoside, which is a pill, and the sample glycoside that is supposed to
be senna. This TLC test will help us prove that the compound we have is a
senna glycoside because even if we proved in the first test that the
compound contains glycone part, and the second that it contains aglycone
(dianothrone), but that doesn’t prove it is senna anthraquinone glycoside,
which is our sample because they are a lot of other compounds, which are
anthraquinone glycosides. So, this identification test will help us prove that
what we have is senna glycoside by comparing the Rf value of a standard
sample and our sample. The result showed that our sample is indeed a
senna anthraquinone glycoside with a companying tailing in our sample,
which indicates that our sample contains impurities.
Conclusion
The process partaken in the experiment proves that for us to identify the
presence of a glycoside so far in our compounds we need to do three
procedures; the first will be general, and it is used to identify if this
compound is within the generic group we want. The second will give
specificity on which category of the generic group the compound belong
too. The third will allow us to specify the exact compound from the
category that the compound belongs too.
References
http://www.yourarticlelibrary.com
LAB REPORT
Alkafeel University/Pharmacy Department