Objective: To establish a method for the determination of soybean isoflavones including daidzein and genistein in foods by high performance liquid chromatography.
Methods: Soybean isoflavones in food samples were refluxed and extracted by 0.5 mol/L hydrochloric acid and ethanol. Soybean isoflavones were chromatographically separated on a C18 column with a mobile phase consisting of methanol and 0.01 mol/L ammonium acetate buffer solution (pH 4.5) (60 + 40), and then detected at 254 nm with ultraviolet-visible detector.
Results: The detection limits were 0.05 microg/ml for daidzein and 0.04 microg/ml for genistein, respectively. The spiked recoveries of the samples were 91.4%-113.1%. The within-day and between-day (n = 6) relative standard deviations were 1.1%-2.8% and 2.9%-5.1%, respectively.
Conclusion: The method is simple, sensitive and applicable to the determination of soybean isoflavones in foods. It also provides an analytical method for isoflavones in functional food and the absorption of phytoextrogens from foods.