Isolation and purification of alkaloids from lotus leaves by ionic-liquid-modified high-speed countercurrent...

An effective high-speed countercurrent chromatography method was successfully established by using ionic liquids as the modifier of the two-phase solvent system. Adding a small amount of ionic liquids significantly shortens the separation time and improves the separation efficiency. The conditions of ionic-liquid-modified high-speed countercurrent chromatography including solvent systems, types and content of added ionic liquids, and ionic liquids posttreatment were investigated. The established method was successfully applied to separate alkaloids from lotus leaves using a two-phase solvent system composed of petroleum ether/ethyl acetate/methanol/water/[C₄ mim][BF₄ ] (1:5:1:5:0.15, v/v/v/v/v). Four alkaloids pronuciferine (1.7 mg), N-nornuciferine (4.3 mg), nuciferine (3.1 mg), and roemerine (2.1 mg) were obtained with the purities of 90.53, 92.25, 99.86, and 98.63%, respectively, from 100 mg crude extract of lotus leaves. The results indicated that the ionic-liquid-modified high-speed countercurrent chromatography method was suitable for alkaloid separation from lotus leaves and would be a promising method for the separation of alkaloids from other natural products.