Isolation of colistin A and B using high-speed countercurrent chromatography

High-speed countercurrent chromatography was successfully applied to the isolation of colistin-A and colistin-B from a commercial colistin preparation. As the first step, TLC and HPLC analysis conditions for the colistin components were established. Using these techniques, a two-phase solvent system composed of n-butanol-0.04M aqueous trifluoroacetic acid (TFA) (1:1) was selected for high-speed CCC, where the concentration of TFA was the major factor in controlling the partition coefficients of the colistin components. Yields of colistin-A and colistin-B were 9 mg each from 20 mg of the commercial sample, and the purity of each component was over 90 %. Fast atom bombardment (FAB) mass spectrometry was utilized to confirm the nature of the isolated components.