A simplified HPLC method for total isoflavones in soy products

Soybeans and soy products are the main source of isoflavones, a well-studied group of phytoestrogens with numerous biological effects. Several methods have been published to quantify soy isoflavones in food samples. We have earlier applied enzyme hydrolysis followed by acid hydrolysis to measure isoflavones as total aglycone equivalents. Alternatively, other published methods have mainly been developed to measure all 12 forms of isoflavones. In order to simplify the analyses, a new extraction method for determination of total amount of isoflavones was developed and validated. Acetyl and malonyl glucosides were hydrolysed to 7-O-glucosides with 80% EtOH containing 1 M HCl to remove the acetyl and malonyl groups. Aglycones and 7-O-glucosides were analysed with HPLC using coulometric electrode array detection.