Separation and purification of two new and two known alkaloids from leaves of Nitraria sibirica by pH-zone-refining counter-current chromatography.

•A pH-zone-refining counter-current chromatography method was established and used for the separation of unpredictable alkaloids from Nitraria sibirica in routine natural products investigation.•pH-zone-refining counter-current chromatography was not only used for separation unpredictable compounds from crude alkaloids, but also used for second purification of highly polar compounds from first separation fractions.•Two new alkaloids together with two known alkaloids were isolated by pH-zone-refining counter-current chromatography.