Introduction
As soy is the most important source of vegetable oil worldwide, it contributes essentially to a balanced diet. Secondary components such as isoflavonoids have a significant positive effect on the hormonal balance. However, adverse effects can occur. The following method for a fast and robust separation of isoflavonoids will facilitate the analysis of these food ingredients.
Structures of 12 isoflavones in soybeansThe isoflavonoids were extracted from the crude matrix by stirring with a 50:50 water/ethanol mixture at room temperature for one hour. After filtration (filter paper No. 5A) the samples were prepared for HPLC analysis by use of a syringe filter (0.2 μm). Initial experiments showed very quickly that the method would be successful using gradient elution with water/acetonitrile with acetic acid to control pH (see figure 2, chromatogram a). Further optimisation was achieved by varying the acetic acid content. Peaks 10 and 11 (Glyciteine and 6´´-O-acetylgenistine) were baseline separated with a high percentage of acetic acid. However, under these conditions the resolution of peaks 7 and 8 (6´´-O-Acetylglycitine and 6´´-OMalonylgenistine) was poor. Reduction of the acetic acid to 3% resulted in near baseline separation of all 7 compounds (see figure 2, chromatogram c).
Influence of acetic acid concentration on soy isoflavone separation>> Download the full Application Note as PDF
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