Separation and purification of isoflavones from a crude soybean extract byhigh-speed counter-current chromatography

A set of isoflavones with a broad range of polarity including daidzin, glyc itin, genistin, acetyldaidzin, glycitein, acetylgenistin and daidzein was s eparated from a crude soybean extract by high-speed counter-current chromat ography using a two-step operation. Three solvent systems were used: chloro form-methanol-water (4:3:2, v/v); chloroform-methanol-n-butanol-water (4:3: 0.5:2, v/v); and methyl tert.-butyl ether-tetrahydrofuran-0.5% aqueous trif luoroacetic acid (2:2:0.15:4, v/v). The first solvent system was used for s eparating less polar isoflavones and the second for more polar isoflavones by eluting the lower organic phase. Genistin and glycitin, which were only partially resolved in the chloroform system, were separated by the third so lvent system. Each isolated component showed 98-99% purity as determined by high-performance liquid chromatography analysis. Their structures were ide ntified by LC-MS. (C) 2001 Elsevier Science B.V. All rights reserved.