Isolation and purification technology of monomeric alkaloids from seeds of sophora alopecuroides L.

After ultrafiltration and decoloration of the acidic water extract of Sophora alopecuroides L. seeds, the monomer alkaloids in it were further extracted by using different solvents and the suitable isolation conditions were searched. Chloroform with pH of 10.5 was found to be the most suitable solvent, and the chloroform extract was then loaded on a silica gel column using chloroform-methanol-ammonia water (5:0.4:0.01, V/V/V) as mobile phase with flow rate of 1 bed volume per hour. During which three peaks were obtained, compounds corresponding to peak 1 and peak 2 were crystallized and recrystallized in acetone and correspondingly crystal A (oxymatrine) and crystal B (oxysophocarpine) were gained with purities over 99%, respectively. Compounds corresponding to peak 3 were re-loaded on a silica gel column once more using acetone-methanol (10:1, V/V) as mobile phase with flow rate of 1 bed volume per hour, and during which another three peaks, peak 4 to peak 6, were observed. Compounds corresponding to peak 5 and peak 6 can not form crystal, and compounds corresponding to peak 4 were crystallized and recrystallized in petroleum and crystal C (sophoridine) was obtained with purity over 95.8%. The molecular structure determinations and the qualitative and quantitative analyses of the obtained monomer alkaloids were conducted by HPLC-MS, IR, melting point measurement and thin layer chromatography techniques.