pH-Zone-refining counter-current chromatography for two new lipo-alkaloids separated from refined alkaline extraction of Kusnezoff monkshood root.

An efficient and refined method for the separation of six aconitine-type alkaloids from the alkaline prepared "Kusnezoff monkshood root" was established. It is the first study that two new lipo-alkaloids were successfully isolated from refined sample by pH-zone-refining counter-current chromatography rather than synthetic method. It was of interest that a great deal of lipo-alkaloids was produced in crude extract from the alkalization of "Kusnezoff monkshood root." A refined sample method was proposed to enrich two types of alkaloids by liquid-liquid extraction, i.e. lipo-alkaloids and monoester-diterpenoid alkaloids. The pH-zone-refining counter-current chromatography was performed with an optimized two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (3:5:4:5, v/v), where upper organic phase was added to 3 mmol/L triethylamine as a retainer and lower aqueous mobile phase was added to 3 mmol/L hydrochloric acid as an eluter. As a result, six aconitum alkaloids, including two lipo-alkaloids (8-lino-14-benzoylaconine, 8-pal-14-benzoylaconine), three monoester-diterpenoid alkaloids (14-benzoylmesaconine, 14-benzoylaconine, beyzoyldeoxyaconine), and one aconine alkaloid (neoline) were acquired from the plant at the same time. The anti-inflammatory activities of the two new lipo-alkaloids were compared to the six alkaloids in vitro, in cyclo-oxygen-ase-2 inhibition assays. The separation mechanism of six alkaloids by pH-zone-refining counter-current chromatography was illustrated.