A simplified hplc

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J. Agric. Food Chem. 1990, 38, 185-190


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A Simplified HPLC Method for the Determination of Phytoestrogens in Soybean and Its Processed Products
Guangjian Wang, Shia S. Kuan,* Octave J. Francis, George M. Ware, and Allen S. Carman Natural Toxins Research Center, Food and Drug Administration, 4298 Elysian Fields Avenue, New Orleans, Louisiana 70122

By using the proposed procedure, phytoestrogens (daidzein, genistein,coumestrol) can be isolated from soybean and its processed products and subsequently quantitated by HPLC without defatting and cleanup of the samples prior to assay. The samples are extracted with acetonitrile-water, and the extract is filtered through a glass fiber filter. The analytes in the filtrate are in turn separated by HPLC on a C,, column and quantified by spectrometry. The method issensitive to 2 ppm of isoflavones with UV detection and 0.5 ppm of coumestrol with fluorescent detection. The recoveries of phytoestrogens in spiked samples ranged between 75 and 110%. The rapidity, simplicity, and low cost of the method make feasible the assay of large numbers of samples in a regulatory laboratory.

Soybean and its processed products have been used as food in the Orient forcenturies. They are known to contain high amounts of protein composed of all the essential amino acids. Soybean oil is also known to be rich in w-3 fatty acids and fat-soluble vitamins. The carbohydrates of soybean are largely polysaccharides and indigestible fiber, which reduces the diseases of the lower gastrointestinal tract. The soybean has been, therefore, acclaimed as a health food. In the UnitedStates, people are now eating more health cautiously. Processed soy products such as tofu, soy milk, soy sauce, etc., are commonly sold in the oriental food store, as well as the local supermarket, and the consumption of these products continues to increase. However, soybeans contain estrogenic compounds, isoflavones, and coumestanes, and there is a significant carry-over of the soyphytoestrogens into its processed products (Murphy, 1982). This means more exposure to phytoestrogens by the consumer. These compounds after ingestion can induce estrus in immature animals or interfere with the normal reproductive processes (Thomson, 1975; Morley et al., 1966). Besides, coumestrol has been suspected to be a tumorpromotor (Verdeal et al., 1980). In order to assure that


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