Large-scale separation of alkaloids from Corydalis decumbens by pH-zone-refining counter-current chromatography

pH-zone-refining counter-current chromatography was successfully applied to the separation of alkaloids from a crude extract of Corydalis decumbens (Thunb.) Pers. using a multilayer coil planet centrifuge (CPC). The experiment was performed with a two-phase solvent system composed of methyl tert-butyl ether (MtBE)–acetonitrile–water (2:2:3, v/v) where triethylamine (5–10 mM) was added to the upper organic stationary phase as a retainer and hydrochloric acid (5–10 mM) to the aqueous mobile phase as an eluter. From 3.1 g of the crude extract, 495 mg protopine, 626 mg tetrahydropalmatine and 423 mg bicuculline were obtained each with a purity of over 93% as determined by high performance liquid chromatography. The structures of the isolated compounds were identified by electron ionization mass spectrometry (EI–MS), high-performance liquid chromatography (HPLC)–electrospray ionisation–mass spectrometry (ESI–MS) and 1H NMR.