Preparative separation of quaternary ammonium alkaloids from Caulis Mahoniae by conventional and pH-zone-refining counter-current chromatography

Abstract

In this work, the preparative separation of quaternary ammonium alkaloids from Caulis Mahoniae by pH-zone-refining counter-current chromatography (PZRCCC) was compared to a conventional high-speed counter-current chromatography (HSCCC). A flow-rate changing strategy was performed in conventional CCC separation with two-phase solvent systems with a solution composed of chloroform–methanol–0.5 mM HCl and water (4 : 1.5 : 2, v/v). Compared to conventional CCC separation, the separation of 3.0 g crude alkaloid extracts was carried out by PZRCCC with solvent system of chloroform–methanol–water (4 : 3 : 3, v/v). The retainer acid and eluter base were optimized by changing the concentration ratios to 60 mM HCl in upper aqueous phase and 7.5 mM TEA in lower phase. From 3.0 g of the crude alkaloid extracts, stepharanine (53.7 mg, 97.4%), columbamine (28.1 mg, 96.5%), jatrorrhizine (150.6 mg, 99.0%), palmatine (169.8 mg, 99.0%) and berberine (157.2 mg, 99.5%) were obtained. The compounds were identified by ESI-MS and ¹H-NMR data. The results indicated that PZRCCC is an excellent separation mode for separating quaternary ammonium alkaloids compared with conventional CCC.