The investigation of germanium based compounds, transition metals and isoflavones within foods

Stephen Dowling

    Research output: Types of ThesisDoctoral Thesis

    Abstract

    The body of work here looks not only at how germanium was present in foods but also the ascertainment of chelation behaviour of germanium compounds and also transition metals with flavonoids. The chelation of germanium with flavonoids, or particularly isoflavones, is a completely novel area and gave some interesting results for chelation with isoflavones with transition metals, an area of research that was completely underexploited until recently. (refer to appendix 1) The Fourier Transform Infrared (FTIR) analysis of foodstuffs for the presence germanium sesquioxide in food and soil and assigning interference bands from biomolecules that can hinder its’ detection were carried out. Results found that the IR band from the carbon oxygen network (C-O-C) band in cellulose can interfere with determination of the germanium oxygen network (Ge-O-Ge) band from germanium sesquioxide. This interference hindered the detection of germanium sesquioxide in a food sample matrix. The Si-O band from silicates present in soil interfered with the determination of the Ge-O-Ge band also. The interferences found in this study make the detection of germanium sesquioxide difficult using FTIR spectroscopy. Atomic Absorption Spectroscopy (AAS) of Cu, Pb, Fe and Ge in soil and food samples showed the variances of content of these elements in a biological matrix. The Ge levels in soil and food were 46.54 - 117.84 μg/g and 1.65 - 642.60 μg/g respectively. Fe, Pb and Cu levels in soil were 16062.03 - 21151.35 μg/g, 32.14 - 247.11 μg/g and 26.98 - 93.21 μg/g respectively. The soil samples are not significantly contaminated in relation to these elements and were within acceptable content limits. Fe, Pb and Cu levels in food were 11.88 - 841.75 μg/g, 0.95 -15.50 μg/g and 2.72 - 18.76 μg/g respectively. The Pb levels in food were mainly quite low and did not pose any hazard to human health. The iron and copper levels were found to be within acceptable nutritional parameters. UV/Vis spectroscopy of isoflavone metal chelates revealed that biochanin A and gensitein chelated with both Cu(II) and Fe(III). Daidzein did not chelate with any of the studied metals. None of the studied isoflavones chelated with Ge(IV) compounds, germanium dioxide or germanium sesquioxide. The Metal/Ligand (M/L)stoichiometries of Fe(III) chelates with genistein and biochanin A were 1:2 and 2:1 from pH of 4.0-9.0. The Metal/Ligand (M/L) stoichiometries of Cu(II) isoflavone chelates with genistein and biochanin A were 1:2, 2:1 and 2:3 at a pH of 4.0-9.0. The copper and iron chelates were synthesised and characterised by elemental analysis, FTIR, thermogravimetric analysis (TGA), proton NMR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS). These studies indicated a 1:2 M/L stoichiometry and suggested the isoflavones bind with the metals at the 4-keto and the 5-OH site. The NMR results were inconclusive with noisy signals observed for the iron chelates and no shifting in the proton peaks themselves. 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition assays showed that copper isoflavone chelates have higher antioxidant activity than free isoflavones while the iron isoflavone chelates showed pro-oxidant activity compared to the free isoflavone. Synergistic DPPH studies with 0.02 mM ascorbic acid revealed copper chelates exhibit reduced antioxidant activity versus free isoflavones whereas the iron chelates showed lower pro-oxidant activity except at a concentrationof 1.0 mM.
    Original languageEnglish
    Awarding Institution
    Supervisors/Advisors
    • Hughes, Helen, Supervisor
    • Regan, Fiona, Supervisor, External person
    Publication statusUnpublished - 2010

    Keywords

    • Germanium compounds, isoflavones

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