QUANTITATION OF PHYTOESTROGENS IN LEGUMES BY HPLC

A fast, sensitive, and precise method is presented for the efficient e xtraction and quantitation of coumestrol, daidzein, genistein, formono netin, and biochanin A from foods by diode array reversed-phase HPLC a nalysis using flavone as internal standard. Acid hydrolysis during ext raction of foods was chosen to convert the various phytoestrogen conju gates into their respective aglycons, facilitating HPLC analysis and a llowing quantitation of total phytoestrogens as aglycons including ori ginally present glycosides, ''free'' aglycons, and those conjugates wh ich are below the detection limit in food plants. Extraction efficienc ies and HPLC conditions were evaluated and optimized, leading to preci sion and spiking recovery values of 3-8% and 94-104%, respectively, de pending on the analyte. Phytoestrogen levels from more than 40 food it ems, mostly legumes, were determined using this method. High levels of daidzein and genistein were found in soy products and black beans, wh ereas sprout items were found to be rich in coumestrol and formononeti n.