Hi! I am Yvonne and I am doing my final year project in university about the qualitative phytochemical content of my sample. one of the test that I have done was the qualitative test for the steroidal presence.
I did the test using Salkowski's Test, and the result that I should be getting if I used the same reagent, same amount and same method for this test is the red precipitate forming on the bottom layer. but somehow, I also got different color such as greenish blue and golden yellow.
p/s: the extraction method was done using 3 different solvents with different polarities.
can anybody explain the formation of different colour? does using different solvent for extractions affect my result? or is it possible that the formation of different color indicates different steroid/phytochemical?
thank you.
In Salkowski reaction red color is due to formation of bi-sulphonic acid of bi-cholestadiene.In this reaction concentrate sulphuric acid removes two molecules of water from two molecules of cholesterol and bicholestadien is formed. Sulphuric acid sulphonates this so due to formation of bi- sulphonic acid of bi-cholestadiene red color is produced,if cholesterol is present.
The sulphuric acid sulphonates the molecule of bi-cholestadiene at 7,7' position of aromatic ring , thus red color bi- sulphonic acid of bi-cholestadiene is formed if cholesterol is present. Nature of concentrate sulphuric acid is hygroscopic due to this it removes two molecules of water from cholesterol. Formation of red color confirms cholesterol. Other colors are due to presence of other phytochemicals.
Please look at the following below links which may help you in your analysis:
http://shodhganga.inflibnet.ac.in/bitstream/10603/6935/12/12_appendix.pdf
https://pdfs.semanticscholar.org/7dae/676046b37041c405a666f885bd7ba5155388.pdf https://innovareacademics.in/journal/ijpps/Vol5Suppl1/6423.pdf
Thanks
Salkowski test shows same results for terpenoids as week as steroids what's the difference in the results for the two compounds,??
When chloroform solution of steroid is treated with concentrated sulphuric acid, red colour is
obtained. Salkowskii test was also used to detect terpenoids. Extract (5 ml) was mixed with chloroform (2 ml), and concentrated sulphuric acid (3 ml) was carefully added to form a layer. A reddish brown coloration of the inter face was formed to show positive results for the presence of terpenoids. formed.
In case of steroid red colour is obtained but in case of terpenoids obtained colour is brownish red.
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