Preparative separation of alkaloids from Gelsemium elegans Benth. using pH-zone-refining counter-current chromatography.

Alkaloids in Gelsemium elegans possess a variety of therapeutic properties, including tumor suppression, analgesic and anti-inflammatory effects. In China, G. elegans has been used for centuries to treat a variety of medical conditions, including chronic pain and skin ulcer. Methods currently used to separate the active components of G. elegans are time-consuming and have low recovery. In the present study, we used pH-zone-refining counter-current chromatography to separate major alkaloids from a crude extract of G. elegans. The two-phase solvent system was methyl tert-butyl ether (MtBE)/acetonitrile/water (3:1.5:4, v/v). Triethylamine (20 mM) was added to the upper organic stationary phase as a retainer. Hydrochloric acid (10 mM) was added to the lower aqueous phase as an eluter. From 1.5 g of crude extract, we obtained 312 mg gelsemine, 420 mg koumine and 195 mg gelsevirine, with purities at 94.8%, 95.9% and 96.7%, respectively, which were determined by HPLC at 256 nm. The chemical identity of the isolated compounds was verified by electrospray ionization-mass spectrometry (ESI-MS), ¹H NMR and ¹³C NMR. These results demonstrated that pH-zone-refining counter-current chromatography is an effective method to separate and purify major alkaloids from G. elegans.