An efficient HPLC method for the quantification of isoflavones in soy extracts and soy dietary supplements in routine quality control.

Food supplements containing soy extracts are increasingly used to treat menopausal complaints. For the quality control of such products a RP-HPLC method for the quantification of daidzein, genistein, glycitein and their respective glucosides and acetylglucosides in soy extracts and nutraceuticals was developed and validated. The extraction of the samples is very simple and avoids time-consuming handling and expensive cartridges or reagents. The compounds are quantified by internal standardization with 4'-hydroxyflavanon which is easily available at a reasonable price. On a base-deactivated C18 column good separation and excellent peak shape of the analytes are achieved in short time by gradient elution with water and acetonitrile. Accompanying substances do not interfere. The method was applied to the analysis of different commercial soy preparations.