Abstract: Highly pure flax lignan was prepared from flaxseeds by n-hexane defatting, ethanol extraction, AB-8 macroporous resin separation and high-speed countercurrent chromatography (HSCCC) purification. Flax lignan was eluted with 80% ethanol from AB-8, and the HSCCC solvent system was composed of tert-butyl methyl ether, n-butanol, acetonitrile and water (1:3:1:5, V/V). The results showed that the impurity content was less than 0.5%, as detected by thin layer chromatography (TLC), high performance liquid chromatography (HPLC), HPLC-DAD-ELSD and HPLC-MS. The purity of flax lignan was between 99.3%–99.5%, as calculated by peak area normalization under various HPLC conditions. The structure was identified by ultraviolet spectroscopy (UV), infrared spectroscopy (IR), high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR) and elemental analysis. The purification method proved to be simple and feasible, and the methods used for purity analysis were accurate and reliable. The flax lignin prepared in this study is enough pure to be used in method validation and quality control.

Key words: flaxseed, lignan, purification, purity analysis, structural identification