We report very nice results of any activity done by using herbal extracts. Do we ever quantify the amount of solvent remaining after the extraction of active constituents. For e.g. I am doing antibacterial study and I have done isolation using Ethanol. Are my results really of the extract or of the amount of ethanol remaining in the extract even after drying? How to validate/ ensure 100% removal of solvent?
Why don't you evaporate the extract in a rotavapor and remove all the solvent traces from the extract. You can also spray dry the extract to remove the traces of the solvent present in it. Always it is better to powder the extract and then dissolve or disperse it in appropriate vehicle for assessing its activity using the vehicle as a blank control for comparison. If these is not possible, then it is better to include a solvent control group which will rule out all the possibilities of solvent traces being responsible for the observed activity. I hope this will help you.
Regards
Use absolute ethanol as control, in parallel with your assay runs. That way you will have an idea to what extent ethanol will affect your bacterial culture. Regards!
Dear Imran
You can follow the above idea (said by Jovale Vincent Tongco). Most of the time I used have the same question while preparing my extract for any bioactivity. In that case I used to keep my sample in Hot air oven at 78 degree Celsius for half hour. It is the boiling point of the solvent (Ethanol). Hence, the solvent may be completely removed from the extract.
The presence of solvent can be quantified using HPLC or GC.
Dear Rajaram thnx .
What if the extract is thermolabile?
I mean to say many a times even in texts it is mentioned with thousands of plant extracts that they exhibit this and that activity. Can any one ensure that it is the activity of the extract and not of the extracting solvent.
Why don't you evaporate the extract in a rotavapor and remove all the solvent traces from the extract. You can also spray dry the extract to remove the traces of the solvent present in it. Always it is better to powder the extract and then dissolve or disperse it in appropriate vehicle for assessing its activity using the vehicle as a blank control for comparison. If these is not possible, then it is better to include a solvent control group which will rule out all the possibilities of solvent traces being responsible for the observed activity. I hope this will help you.
Regards
Organic solvents generally used for extraction of plant materials are volatile at different degree of temperature. They can be completely removed once the extraction is complete. For removal, normal distillation, distillation under reduced paper, spray drying and finally direct heating at controlled temperature is done to get rid of even trace of solvent prior to any kind of bioassay. The extract totally free from trace of residual solvent is then used with appropriate vehicle for biological studies. Further, it is always appropriate to assess bioactivity using the vehicle as a blank control for comparison. Also, a solvent control group may also be included as suggested by Alok in order to rule out all the possibilities of solvent traces deem to be responsible for observed activity.
You have to evaporate all the solvent from the extract, before you start testing it.
Even while doing experiments, you need to keep that solvent as a negative control, into which your test extract has been reconstituted. You may refer our following publication:
T. Wadhwani, K. Desai, D. Patel, D. Lawani, P. Bahaley, P. Joshi & V. Kothari. 2009. Effect of various solvents on bacterial growth in context of determining MIC of various antimicrobials. The Internet Journal of Microbiology, Volume 7 Number 1
- Badges
- Science topic
- Similar topics
- Analytical Chemistry
- Extraction