Isoflavones are found primarily in plants of soy (Glycine max), red clover (Trifolium pretense), and Kudzu (Pueraria lobata). 12 major isoflavones found in these plants are daidzein, glycitein, genistein and their respective glucoside and malonyl- and acetyl- glucoside derivatives. The structures of 12 isoflavones and an internal standard (apigenin) are shown in Figure 1. These hormone-like compounds are often used in remedies to reduce menopausal and post-menopausal symptoms.
Standard methods for isoflavones in dietary supplements have been established by standard organizations such as USP(1) and AOAC(2). These methods use reversed-phase LC with C18 columns and ultraviolet and visible light (UV-Vis) spectroscopy for separation and quantitation. Because of the close structural similarity of this group of compounds, the chromatographic run times of these methods are over 70 minutes long. It is highly desired to develop a fast isoflavone analysis method.
This study demonstrates the method transfer of the USP method on an ACQUITY® ArcTM system. The analysis time, including column wash and equilibration, is only 18 minutes with this fast method. Waters® QDa® mass detector was used in this study. The benefits of mass detection in peak identification and method optimization are also highlighted.