Alkaloids are present either as a free base or as a salt form.

Alkaoidal salts are soluble in polar solvents while base are soluble in nonpolar solvents like Petroleum ether, n-Hexane, Benzene, Chloroform, etc....

First of all mix your dried methanolic extract with acid solution so it will convert most of the alkaloids in salt form.

As a salt alkaloids remain in aqueous acidic layer when it will be partitioned with non polar solvent like pet. ether. Partitioning with Pet. ether remove non alkaloidal impurities so discard pet ether layer. Make aqueous layer alkaline with suitable Alkali solution. extract it with organic solvents like pet ether. evaporate pet ether and dissolve residue in acid. (Repeat this step as needed i.e. Salt to Base, Base to Salt,,,,,,,and so on.)

Then take alkaloid as a salt form (acidic layer).

Make aqueous acidic layer alkaline with suitable Alkali solution.

Adjust pH at 8--------> then Partition it with non polar solvents so alkaloids converted to free base at this pH comes with non polar layer, separate it.

Take remaining aqueous layer, make it alkaline again and

adjust pH to 9 --------> repeat as said above.

Repeat same process at different pH.

This method will easily give pH based separation of alkaloids as per my knowledge.

Alkaloids are present either as a free base or as a salt form.

Alkaoidal salts are soluble in polar solvents while base are soluble in nonpolar solvents like Petroleum ether, n-Hexane, Benzene, Chloroform, etc....

First of all mix your dried methanolic extract with acid solution so it will convert most of the alkaloids in salt form.

As a salt alkaloids remain in aqueous acidic layer when it will be partitioned with non polar solvent like pet. ether. Partitioning with Pet. ether remove non alkaloidal impurities so discard pet ether layer. Make aqueous layer alkaline with suitable Alkali solution. extract it with organic solvents like pet ether. evaporate pet ether and dissolve residue in acid. (Repeat this step as needed i.e. Salt to Base, Base to Salt,,,,,,,and so on.)

Then take alkaloid as a salt form (acidic layer).

Make aqueous acidic layer alkaline with suitable Alkali solution.

Adjust pH at 8--------> then Partition it with non polar solvents so alkaloids converted to free base at this pH comes with non polar layer, separate it.

Take remaining aqueous layer, make it alkaline again and

adjust pH to 9 --------> repeat as said above.

Repeat same process at different pH.

This method will easily give pH based separation of alkaloids as per my knowledge.

Thank you very much Mr. Satani, this is a very important info for me indeed.

I think you will also get a good result if you concentrate your methanolic extract and then resuspend it in a basic aqueous solution. Next, you can now extract your alkaloids to organic imiscible solvents by partition.

Pl find attached methodology for the extraction of alkaloids according to Harborne (1983).

In addition to Dr. Satani's method, also consider using a strong ion exchange resin since this may resolve some of the alkaloid families from each other.

For example, see: http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN40_Purification_of_Alkaloids_with_RediSep_Rf_SCX_Columns.pdf

Thank you very much to all of you. Such a nice informations!!!