title: Detection and structural characterization of thermally generated isoflavone malonylglucoside derivatives.
abstract: Malonylglucoside isomers were identified by high-performance liquid chromatography with ultraviolet/mass spectrometric detection and nuclear magnetic resonance (NMR). The formation and interconversions of the isomers were monitored in heated buffer and soymilk systems. Two positional or steroisomers of malonylgenistin and malonydaidzin, showing similar UV spectra and molecular weights yet different fragmentation patterns, were detected. NMR characterization of the malonylgenistin isomer revealed its structure to be 4''-O-malonylgenistin, suggesting a malonyl migration from the glucose-6 position to the glucose-4 position. Interconversions of malonylgenistin and its isomer were observed in both buffered and soymilk systems. While malonylgenistin partially converted to the isomer upon thermal treatment, conversion of the isomer to malonylgenistin was more spontaneous. The malonylgenistin isomer represented 6-9% of the total calculated genistein content in soymilk heated at 100 °C for various periods of time. Consequently, disregarding the content of malonylglucoside isomers in processed soy matrices can lead to isoflavone underestimation and misinterpretation of the biological contributions.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, Twin Cities, Saint Paul, Minnesota 55108-1038, USA.
authors.forename: Vamsidhar
authors.initials: V
authors.lastname: Yerramsetty
authors.forename: Kevin
authors.initials: K
authors.lastname: Mathias
authors.forename: Mirko
authors.initials: M
authors.lastname: Bunzel
authors.forename: Baraem
authors.initials: B
authors.lastname: Ismail
mesh_terms: D005960:Glucosides / Q000737:chemistry*; D006358:Hot Temperature; D007529:Isoflavones / Q000737:chemistry*; D007536:Isomerism; D015394:Molecular Structure; D041942:Soy Milk / Q000737:chemistry*
chemical_list: D005960:Glucosides; D007529:Isoflavones