RAPID HPLC ANALYSIS OF DIETARY PHYTOESTROGENS FROM LEGUMES AND FROM HUMAN URINE

Due to growing evidence suggesting that phytoestrogens might protect a gainst various cancers, particularly against breast and prostate cance r, it is important to measure the exposure of populations to these com pounds by determining levels in food and in human tissue or body fluid s to assess the possible cancer protective properties of these agents. Therefore, we developed a simple and fast procedure to extract and si multaneously hydrolyze phytoestrogens and their conjugates from food i tems, and present a fast and selective high-performance liquid chromat ography (HPLC) method for precise determinations of the most common di etary phytoestrogens genistein, biochanin-A, daidzein, formononetin, a nd coumestrol using flavone as internal standard. For the first time H PLC was applied to measure these phytoestrogens and their most abundan t metabolites equol and O-desmethyl-angolensin from human urine. The p roposed methodology has been evaluated for losses due to thermal degra dation during extraction and hydrolysis and due to sample handling dur ing the entire work-up including solid phase extraction, and values ar e given for inter- and intra-assay variability. We present isoflavonoi d levels of most common peas and beans used In ''western'' and ''easte rn'' diets and compare isoflavonoid and coumestrol levels of raw, cann ed, and cooked foods which can be used in future epidemlological studi es. We also determined human urinary levels with our methodology compa ring values before and after soybean intake.