Drops of the Dragendorff reagent have been added to a crude plant extract (powder macerated in water then filtrated). The colour of the precipitate seems too clear to me (See the picture) ! Your comments please...
Hello,
I used the Dragendorff reagent to check the presence of alkaloids in my extracts and the positive result I mean the color what you should have if there is Alkaloid in your sample is the formation of reddish brown precipitated orange color with préciptation.
(2 ml of extract was added 1 ml of Dragendorff reagent along the side of the test tube. Formation of reddish brown precipitated orange or orange indicates test as positive (Roopalatha and Vijay, 2013)).
You can also check this paper to have more detail.
Good luck.
AbdelOuahab
Thank you dear Abdelouahab. But what about my result, I have a precipitate but the colour is little bit different, the test is qualitative so I don't think that the ratio of the reagents affect the result dramatically!
As you say, it is qualitative assay so you can put +++ for the high presence and ++, + and - for the absence.
It stays a qualitative information so if you steel interest to this kind of secondary metabolites I advise you to extract the alkaloid after bibliographic research about this spice of plant and you make quantitative dosage.
For your sample, it seems a positive result.
We use methanol or another alcohol to extract alkaloids, the maceration in water doesn’t give a good extraction , and Dragendorff reagent is for alkaloids detection. i advise you to repeat the extraction with methanol
Dragendorff reagent is commonly used to identify the presence of alkaloids in plant extracts that exhibit a reddish brown color when sprayed with the reagent. The heavy metal atom (BiI4) combines with the nitrogen in the alkaloid to form ion pairs. This ion pair forms an insoluble orange red colored complex.
I have attached a dragendorff spry picture on the TLC Silica plate that they run by ethyl acetate: hexane: ethanol : ammonia solution 100:5:5:2.5 as follows:
- Badges
- Science topic
- Similar topics
- Biological Science
- Botany
- Pharmaceutical Botany
- Plant Extracts