I read papers that state that the iridoids are soluble in n-butanol such that the n-butanolic fractions contains the bitter iridoids. I have the aqueous fraction separated from the methanolic extract, so I did the liquid liquid separation but found that they are miscible and can be separated...is there any solution or my procedure is wrong? The hexane fraction separated gave the precipitate after few hours of stand?
How much n-butanol and water did you use? That solvent can carry quite a bit of water- makes it difficult to evaporate your extract. I imagine that water can also carry n-butanol as well. Too little of either solvent compared to the other would create a single phase.
The last reason that has been posted may be the reason...the fact is that i could not get any papers related to the procedure and analytic features...i used 100ml aqueous to 30ml butano...is it appropriate or what may be the appropriate volume to be used in the process??? Can further link to get the paper be suggested... Thank you verymuch
I would have tried a 1:1 ratio of butanol:water to start. Unfortunately, I did this work a long time ago so I forget the exact proportions I used.
This reference: J. Nat. Prod., 2004, 67 (3), pp 479–480 suggests 1 part water to 0.5 part n-butanol : "The extract was suspended in 1 L of H2O, and the suspension was extracted with EtOAc (5 times with 0.5 L each) and then with n-butanol (n-BuOH) (5 times with 0.5 L each). "
I would suggest fractionation of methanolic extract on silica gel column using a solution of n-butanol saturated with water as eluting solvent. You may try on TLC if this system give a good separation.
Residual methanol in the aqueous phase could be a problem since it is miscible with both water and butanol. You could assist the phase separation by adding ions (e.g. NaCl) to the aqueous phase.
Good Luck!
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