CHAPTER 16. The Determination of Isoflavones in Supplemented Foods: An Overview

Isoflavones are a group of phytochemicals found in many plants that belong to the family of phytoestrogens due to their structural similarity to estradiol. These natural substances may offer several benefits to human health. Daidzein, genistein and glycitein are present as free forms or derivatives in foods containing soy or soy protein extracts. The analysis of isoflavones has become more complex due to the fact that preparations contain isoflavones from multiple sources. Isoflavones are present in foods and dietary supplements as free compounds, glucoside derivatives, 6″-O-malonyl-7-O-β-d-glucoside derivatives and 6″-O-acetyl-7-O-β-d-glucoside derivatives. The main isoflavones used in supplemented foods are daidzein and genistein, their glucosides, daidzin and genistin, as well as their methyl ether precursors, formononetin and biochanin A. Different extraction techniques have been applied to the isolation of compounds from food samples, and LC with ultraviolet detection has been traditionally used for the identification and quantification of isoflavones in routine analysis. In recent years, MS has become the leading technique used in the detection and identification of these compounds. In this Chapter, we provide an overview of the methodologies used for the determination of the most common isoflavones present in supplemented food.