Quantitative determination of isoflavones and coumestrol in soybean by column liquid chromatography

Four different stationary phases and a variety of solvents in varying propo rtions were examined in this study. Daidzein, genistein, formononetin, bioc hanin A and coumestrol were separated within 24 min on a phenyl column with acetonitrile-water (33:67, v/v) as eluent. The proposed method showed an a cceptable repeatability with a RSD of quantitation <6%. The mean recoveries of daidzein, genistein, formononetin, biochanin A and coumestrol from soyb ean ranged from 89 to 104%. The identity of the individual analytes was con firmed by LC-MS-MS. The four isoflavones and coumestrol were isolated from soybean by hydrolysis with acid and heat. Neutralization of the soybean sam ples prior to identification did not alter the concentration of daidzein an d genistein in soybean. (C) 2000 Elsevier Science B.V. All rights reserved.