The extract was obtained using silica gel column purification. The fraction was collected with methanol. It was showing a streak in TLC. I wish to crystallize a purified fraction from plant extract. I have no success with liquid diffusion and re-crystallization. I now plan to do preparative-tlc. Can anyone share your experience/methods to obtain single crystals.
generally its very difficult to isolate polar compounds. I too faced the same problem. What I can suggest you is, if you have preparative HPLC facility do isolate using HPLC or else use amberlyte and sephadex LH-20. A better method to isolate polar compounds in the absence of preparative HPLC. You can get so many papers.
Good luck
generally its very difficult to isolate polar compounds. I too faced the same problem. What I can suggest you is, if you have preparative HPLC facility do isolate using HPLC or else use amberlyte and sephadex LH-20. A better method to isolate polar compounds in the absence of preparative HPLC. You can get so many papers.
Good luck
just see if its sugar by using acid anisaldhyde reagent well i dont remmber the mobile phase so u search sugar mobile phase and para anisaldehyde reagent in literature you will see white streak in red background there might be other compounds which is not visible so u failed recrystallisation.
It is not much easy to crystallise a phytochemical only through column. very rare cases you can. It is also based on the type of it. As you say if you are not provided with Prep.HPLC can go with Prep.TLC. Even then to get much pure one go for two to three times elution with TLC itself.
All the best
Maybe you should consider fractionating your methanol extract into a hexane-, a dichloromethane-, and a methanol-soluble fraction. After that initial fractionation, you can run a TLC of each fraction to see how well individual compounds in each fraction separate. If you observe streaks, sometimes it helps to add a few drops of triethylamine to your eluent mix. This may give better separated spots.
Once you've found the best separation method by TLC, you can apply the same mixture on column chromatography.
Do you have any reason to believe that your compound is solid at room temperature?
We usually use the prep HPLC for the polar fractions obtained by methanol or ethanol. if you have enough sample, you can use the reverse phase column. I wouldn't suggest using prep TLC because it will give a streak and will not separate well. to recrystallize, you can try another set of solvents for the vial-in-vial method or you can try dissolving it in toluene and freezing it overnight.
Actually for crystallization the compounds purity should be more than 70%. Try to do recolumn on RP-18. So that you will get more purified fractions. Then try crystallization.
Dear Prasanna,
Please freeze dried your extract. I think you will get the clear picture (after freeze drying) that your extract can solidify in crystallized form or not.
please extract leave with methanol and evaporate using vacuum evaporation. by vacuum liquid chromatography, fractionate the methanol extract on silica (270-400 mesh) with gradually polarity increasing. test the fraction on TLC to see which fraction give interested spots. then select that fraction to do CC or crystallization., and there is good chance to get crystal
Good luck
Refer: http://www2.volstate.edu/CHEM/2010/Labs/Caffeine_Extraction.htm
Dear Prof. Bruce,
It was solid at room temperature. But it has some stickiness. I am not drying it harshly so that it won't affect the phytochemical profile undesirably.
Dear All,
Thanks very much for your kind help. I am taking your suggestions and hoping for single crystals.
Dear Noura S. Dosoky,
I have tried using toluene for some extract. But it will take a very long time to evaporate in a refrigerator. Then also, these fractions were not soluble in toluene. Thank you for your suggestions on TLC.
Dear Prof. Randolph Arroo,
Thanks very much for the partition methods. I have also used chloroform, ethylacetate, methanol partition. I will try again. I hope there may be impurities.
If it was a sticky 'solid' at room temperature, there's some hope! You should probably determine in what solvents it dissolves easily and in which it is hard to dissolve, and then look for something intermediate (possibly dissolving in a medium-high solubility medium and precipitating with something else), with plenty of 'cooling and scratching'. Be patient! It may take a very long time!
The TLC streaking may also indicate some amines at work. It might be worth adding some aqueous ammonia or triethylamine to decrease the silica acidity to give a better TLC run.
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