Isoflavones quantification in rainbow trout muscle by QuEChERS tecnique and liquid chromatography coupled with mass spectrometry

The interest in soy isoflavones, especially genistein and daidzein, has increased since scientific data showing a wide range of biological activities of these phytoestrogens. The aim of the present research was to develop and validate a new analytical method for the identification and quantification of isoflavones for the first time in rainbow trout muscle, by the QuEChERS methodology, followed by liquid chromatography coupled with electrospray ionisation mass spectrometry in positive ion (LC-ESI–MS) analysis. The analytes monitored and quantified were Daidzein, Daidzin, Genistein, Genistin, Glycitein and Glycitin. The method was validated according to the criteria of European Commission Decision 2002/657/EC, and the parameters evaluated included linearity, precision, matrix effect, limit of detection and quantification, absolute recovery and robustness. The limit of quantification was fixed at 0.2 μg kg−1 for all isoflavones. The method was applied to 26 real samples of the rainbow trout muscle, and the correlation between the presence of isoflavones, both free and conjugated forms, in muscle and diet with soybeans and soy derivatives was established. This method is suitable for more accurately determining the human exposure to dietary isoflavones from products of animal origin.