Calystegine alkaloids fractions

Calystegines, in common with other classes of polyhydroxy alkaloids, are highly water-soluble and cannot be isolated by conventional alkaloid separation techniques which employ add-base pardoning methods with non-hydroxylic organic solvents [20], Ion-exchange chromatography is therefore extensively employed for separation of the alkaloid fraction from neutral and addic compounds present in the extract [21,22]. 

In situations when analysis is required to establish the presence and identity of calystegines in a plant extract it is not necessary to utilize a complex series of chromatographic separations. The plant material can be extracted with methanol or methanol-water and passage over a Dowex 50W-X8 column with dilute ammonium hydroxide as eluant provides substantial purification, yielding the alkaloid fraction, including other polyhydroxy alkaloids, contaminated only by basic amino adds. The extract can thus be rapidly prepared for analysis [29,30]. 

The hydrophihc calystegines are extracted with water or methanol-water solutions. After centrifugation, the volume of the supernatant is reduced, treated with skin powder, filtered, and then applied to columns of strongly acidic cation exchange resin for purification. The nonbinding compounds are removed with water and alkaloids are eluted with 3.5% aqueous NH3. After drying, the alkaloid fraction has to be silylated for further GC-MS analysis [20]. 

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