Isolation of anti-tumor compounds from the stem bark of Zanthoxylum ailanthoides Sieb.Zucc. by silica gel column and counter-current chromatography

Silica gel column chromatography combined with high performance counter-current chromatography (HPCCC) was employed for the separation of potential anti-tumor compounds from a petroleum ether fraction of a crude extract of Zanthoxylum ailanthoides Sieb. & Zucc. This traditional Chinese medicine was recently found to display high inhibitory activity against A-549 human cancer cells in vitro and Lewis lung cancer in vivo. A 75% aqueous ethanol extract of the stem bark of Z. ailanthoides was fractionated with petroleum ether, ethyl acetate and n-butanol. In this paper, the petroleum ether fraction was pre-separated by silica gel column chromatography with a petroleum ether–ethyl acetate gradient. Two fractions were further separated and purified by HPCCC using n-hexane–ethyl acetate–methanol–water (3:1:2:1, v/v) and petroleum–ethyl acetate–methanol–water (8:6:7:7, v/v). Finally, coumarins and lignans including luvangetin, xanthyletin, hinokinin and asarinin were isolated and identified by MS, 1H and 13C NMR. In total, 56 mg of xanthyletin (1), 140 mg of hinokinin (2), 850 mg of luvangetin (3) and 74 mg of asarinin (4) were obtained from approximately 50 g of petroleum ether extract, in 96.0%, 94.0%, 99.0% and 94.0% purity, respectively, as determined by HPLC. The separation method proved to be efficient, especially for those minor components.