Extraction and purification of isoflavones from soybeans and characterization of their estrogenic activities

Soybean isoflavones have multiple beneficial health effects especially on estrogen-deficient diseases such as menopausal symptoms. In this study, isoflavones were produced from soybean flour, and the extraction and purification parameters were optimized to give a high yield of total isoflavones, about 0.62 mg of aglycones/g of soybean flour, which is >2 times the initial yield. HPLC analysis and MTT cell proliferation assay using MCF-7 cells revealed that the product thus obtained not only contained a high content of isoflavone aglycones but also had estrogenic activity. MTT data also revealed that both genistein and daidzein exhibited estrogenic effects at lower concentrations and antiproliferative effects at higher concentrations, and 1 microM genistein and 10 microM daidzein exerted significant estrogenic activities, which were not more than that of the endogenous level of 17beta-estradiol (E2). The production method developed can be used as a guideline for manufacturing soy isoflavones, and the MTT assay was demonstrated to be suitable for quality control on isoflavone products. The results on the estrogenic properties of isoflavones can be used as reference data for their effective and safe usages in estrogenic therapy.