Analysis of Isoflavones in Soy Foods

Analysis of Isoflavones in Soy Foods Basic Protocol 1 Solvent Extraction of Isoflavones in Their Natural Forms 11.6.1... 

Wang J and Sporns P. 2000b. MALDI-TOF MS analysis of isoflavones in soy products. J Agric Food Chem... 

A systematic investigation in extraction and analysis of isoflavones from soy-containing foods and nutritional supplements. 

In a study of retail soy foods, Murphy et al. (1999) optimized extraction of isoflavones and found that the amount of water included in the mixture of acetoni-trile-0.1 N HCl-water affected the yield of isoflavones in various foods matrices. Two grams of samples were extracted with 10 ml acetonitrile, 2 ml of 0.1 N HC1 and an amount of water. The optimal amount of water ranged from 5 to 10 ml, depending upon the type of food matrix. The standard deviation of the optimized extractions ranged from 0.6% to 4.8% for total daidzein and 0.2-3.5% for genistein analysis. HPLC with a C18 column was used to separate the isoflavones, which were... 

Quantification. For accurate quantification, a standard curve of peak area versus concentration should be constructed for each standard using the same chromatographic conditions (e.g., wavelength and solvent) as for the samples under analysis. The concentration range of standard curves should be determined according to both the isoflavone level of soy food samples and dilution factors during sample preparation such that the UV absorbance of the injected sample is within a range of 0 to 1. The appropriate standard curve can then be used to calculate the quantity of isoflavones represented by each HPLC peak in the sample. 

Hubert, J., Berger, M., and Daydea, J. 2005. Use of a dimplified HPLC-UV analysis for soya saponin B determination Study of saponin and isoflavone variability in soybean cultivars and soy-based health food products. J. Agric. Food Chem. 53 3923-3930. 

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