Two-stage fractionation of polar alkaloids from Rhizoma coptidis by countercurrent chromatography considering the strategy of reactive extraction

• A new way of selective purification of polar components from complex natural sources was offered.
• The possible mechanism for reactive extraction on countercurrent chromatography was proposed.
• High hydrophobicities of the formed salts allowed the targets to transfer from the aqueous phase to the organic.
• Five polar alkaloids from Rhizoma coptidis were separated by countercurrent chromatography in two stages.

Separation of polar alkaloids by countercurrent chromatography (CCC) is challengeable due to their close partition behaviors in solvent system. In this paper, a two-stage method for isolation of epiberberine, jatrorrhizine, palmatine, coptisine, and berberine from Rhizoma coptidis was presented. The first stage separation performed on CCC was based on the principle of reactive extraction. Trifluoroacetic acid was acted as a modulator to selectively react with alkaloids, which changed their partition coefficients in solvent system. Purified epiberberine and other partially separated targets were eluted by ammonium adjusted mobile phase. In the second stage, four alkaloids were purified in pH-zone-refining CCC mode. All the targets collected were over 97% pure determined by HPLC. The method developed demonstrates performing of reactive extraction on standard CCC as an option for separation of polar alkaloids from medicinal plants.