Most of the times we dissove extracts from plants or other sources with Acetone or DMSO. Observations show that when relatively non-polar solvents (n-Hexane, Pet Ether, DCM etc) were used during extractions, then the extracts will dissolve best in Acetone or 10%DMSO.
However, during preparations of working solutions and further dilutions on Microtitre plates, the solubility of these extracts decreases and precipitates can be observed upon centrifugation. These precipitates are compounds which dissolved in Acetone or 10%DMSO but they can not stay in solution as the compositions of these solvents get lower. (Maybe they have antimicrobial potentials)
On the other hand, conventional antibacterial agents which are water insoluble are usually solubilized through Synthetic and Formulation approaches eg. Forming their salts. This is not so possible with crude extracts.
If gold standard MIC testing methods such as Broth Microdilution assays are mostly using water based media eg. MHB, what reliable options do we have to zoom in probably potential antimicrobial combounds present in nature but insoluble in water?
Any similar or different encounters?
Article Methods for in vitro evaluating antimicrobial activity: A review
Thanks @T. H. Al-Noor for a nice article that I once came across with. However, It highlights a variety of methods but not the question under this discussion .
This subject was discussed multiple times in RG, for example see:
https://www.researchgate.net/post/Methanolic_or_hydro_alcoholic_extraction
Also search "extraction antimicrobials" in the RG webpage...
Yes it has, unfortunately the discussions/questions refered to are mostly around what solvent to choose when aiming at a particular activity testing or what to solvent to use to solubilize extracts.
You might miss components, as a plant contains molecules of all polarity as you well know. So using just one solvent to test is missing the mark of other components.
Plants also have synergistic effects between their components so you might find some in one solvent but miss others that are synergistic.
I would also look up CO2 extractions, as they offer a low polarity extraction that is non-toxic to animals.
Hoping this helps...
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