Isoflavones in soy

MURPHY p A, SONG T, BUSEMAN G, BARUA K (1997) Isoflavones in soy-hased infant formulas. JAgric Food Chem. 45 4635-8. 

The major isoflavones in soy are genistein, daidzein and glycitein (reviewed by Setchell, 1998 Setchell and Cassidy, 1999). Isoflavone content varies among soybean varieties, growing conditions and soil (Wang and Murphy,... 

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

Toro-Funes N. Odriozola-Serrano I. Bosch-Fuste J. Latorre-Moratalla M.L. Veciana-Nogues M.T. Izquierdo-Pulido M. Vidal-Carou M.C. Fast simultaneous determination of free and conjugated isoflavones in soy milk by UHPLC-UV. Food Chemistry, 2012, 135, 2832-2838. 

Micke, G. A., Fujiya, N. M., Tonin, F. G., de Oliveira Costa, A. C., and Tavares, M. F. M. (2006). Method development and validation for isoflavones in soy germ pharmaceutical capsules using micellar electrokinetic chromatography. /. Pharm. Biomed. Anal. 41(5), 1625—1632. 

Before 1990 the composition of isoflavones in soy foods was thought to be largely determined by whether the food had been fermented. Fermented foods (e.g., miso and tempeh) contain the unconjugated isoflavones agycones, while non-fermented food (e.g., tofu, soy flower, and soy milk) contain the conjugated glucoside. Subsequent experiments have demonstrated that fermentation of soy decreased the isoflavone content of the food product, but increased the urinary isoflavonoid recovery, suggesting that fermentation increases availability of isoflavones in soy (Slavin et al., 1998). 

MALDI-TOF-MS has been used to identify and quantify other anthocyanins in foods.When the anthocyanin content of highbush blueberries at different stages of anthocyanin formation were analyzed by both HPLC and MALDI-TOF-MS, it was found that both techniques provided comparable quantitative anthocyanin profiles. While HPLC could distinguish anthocyanin isomers, MALDI-TOF-MS proved to be more rapid. MALDI-TOF-MS has also been used to identify the isoflavones in soy samples. In a comparison of several matrices, 2, 4, 6 -trihydroxyacetophenone (THAP) and 2,5-dihydroxybenzoic acid... 

There have been some concerns expressed regarding the possible health consequences in adulthood (endocrinological and reproductive outcomes) of early-life isoflavone exposure from soy-based infant formula. The daily exposure of infants to isoflavones in soy-based infant formulas is 6- to 11-fold higher on a body weight basis than the dose that has hormonal effects in adults consuming soy foods. " However, evidence from adult and infant populations indicates that dietary isoflavones in soy-based infant formulas do not adversely affect human growth, development, or reproduction. 

Chen A, Rogan WJ. Isoflavones in soy infant formula a review of evidence for endocrine and other activity in infants. Annu. Rev. Nutr. 24, 33-54, 2004. 

Knowledge of the pharmacokinetics of isoflavones in soy foods is essential for making recommendations regarding efficacy in clinical studies. Die plasma half-life of daidzein and genistein, measured from their plasma appearance and disappearance curves, is 7.9 h in adults peak concentrations occur 6-8 h after administration of the pure compounds [93] with peak concentrations ranging from 80 to 800 ng/ml (after a single oral dose of 50 mg of pure isoflavones). 

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

Use the area of each isoflavone peak and the calibration curves to calculate the isoflavone concentrations in the sample. Calculate the final concentration of isoflavones in soy food by considering the dilution factor during sample preparation. 

By comparing the chromatogram from enzymatic hydrolysis with that in the absence of enzymatic hydrolysis, the completeness of hydrolysis by enzymes and the total isoflavones in soy food extract can be determined (see Basic Protocol 3). 

HPLC is the method of choice for the analysis of isoflavones in soy products. HPLC is fast, reproducible, requires small sample sizes, and can be used for both qualitative and quantitative analysis as well as for separation purposes. 

Klump, S., Allred, M., MacDonald, J., and Ballam, J. 2001. Determination of isoflavones in soy and select foods containing soy by extraction, saponification, and LC. Collaborative study. J. AOACInt. 84 1865-1883. 

Nguyenle, T., Wang, E., and Cheung, A.P. 1995. An investigation on the extraction and concentration of isoflavones in soy-based products. J. Pharm. Biomed. Anal. 14 221-232. 

Murphy PA, Barua K, Hauck CC. 2002. Solvent extraction selection in the determination of isoflavones in soy foods. J Chromatogr B 777 129-138. 

Klejdus B, Vacek J, Benesova L, Kopecky J, Lapcik O, Kuban V. 2007. Rapid-resolution HPLC with spectrometric detection for the determination and identification of isoflavones in soy preparations and plant extracts. Anal Bioanal Chem 389 2277-2285. 

Once the benefits of a key component in food are documented, the challenge is to increase its concentration, and presumably its benefits, while maintaining safety. For example, isoflavones in soy are phytoestrogens with a chemical structure similar to estrogen. Isoflavones may reduce cholesterol, but what is the risk of increasing the intake of a compound that may modulate estrogens Knowledge of the toxicity of functional food components is crucial to improve their benefit-risk ratio. The efforts... 

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