104C-24 |
The effects of solvent polarity and acidity on the extraction efficiency of isoflavones from soybeans (Glycine max). |
F. LIN, Department of Nutrition and Food Science, University of Maryland, 0112 Skinner Bldg Room 044, College Park, MD 20742 and M. M. Giusti, Nutrition and Food Science, University of Maryland. Isoflavones found in high concentrations in soybeans have received great attention due to their potential beneficial effects in human health. The relative biological activity of these compounds depends on their chemical structure. Extraction and quantitation of isoflavones in their intact form are of crucial importance. However, no agreement has been found on the best extraction solvent systems. Our objectives were to compare the extraction efficiency of widely used solvent systems for isoflavone analysis and to evaluate the effects of polarity and acidity on the recovery of isoflavones from soybeans. Isoflavones were extracted from pulverized Manokin soybeans using three different solvent systems: 80% methanol; 83% acetonitrile; 58% acetonitrile. To test the effect of acidity, the same systems were acidified and their extraction efficiency was compared. Pulverized soybeans were stirred for 2hr in each solvent system before filtration and concentration by rotary evaporation. The extract was re-suspended in 16% acetonitrile, and analyzed by HPLC. Recovery of pure standards were evaluated with all solvent systems to account for changes during the process. We found significant differences in the isoflavone extraction by the different solvent systems. The 58% acetonitrile with or without acidification extracted the highest amount of isoflavones in all forms, while 83% acetonitrile extracted the lowest amount of isoflavones in all forms except for aglycone form. Acidification significantly reduced the recovery of malonylglucoside forms. The recovery study revealed the chemical transformations of acetylgenistein into genistin and part of the genistin into genistein during the extraction by acidified solvents. Isoflavones have been correlated with health beneficial effects, resulting in increased demand for soybean products. The predominant chemical form of isoflavone present may affect both, biological activity and flavor. Therefore, choosing the solvent system (including polarity and acidity) that can accurately quantify the amounts of individual isoflavones present in these products is paramount.
Session 104C, Fruit & Vegetable Products: Vegetables (Processed)
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