Trace-level determination of flavonoids and their conjugates: application to plants of the Leguminosae family
Rijke, E. de
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The research described in the dissertation is part of the project 'Wetlands in the Randstad', a cooperation between the Faculty of Earth and Life Sciences, the Faculty of Exact Sciences, the Faculty of Economics and the Institute of Environmental Studies of the Free University Amsterdam, which focuses on the effects of flooding or 'vernatting' of polder and wetland areas in the densely populated Randstad area of the Netherlands, to restore their ecological value. The aim of the research was to develop adequate methods of analysis for flavonoids including their conjugates in complex matrices, in particular wetland plants. In the end, these methods were used to study the potential of flavonoids as indicators for ecological changes due to vernatting. The flavonoids were selected because they are chemically well-defined compounds and as secondary metabolites they play an important role in plants as defence and signalling compounds in e.g. reproduction, pathogenesis and symbiosis. Furthermore, they possess chromophoric groups so that they can be studied by UV/Vis spectrometry and exhibit useful fragmentation in mass spectrometry; some flavonoids show native fluorescence. In this dissertation, flavonoids in plants of the Leguminosae family, which commonly occur in Dutch wetland areas, are studied using various hyphenated analytical methods. The study comprises (i) optimization of extraction procedures, with emphasis on the stability of selected flavonoids; (ii) research on UV absorbance, fluorescence and NMR spectroscopy as well as (tandem) mass spectrometry of flavonoids in order to find optimal detection conditions and, as a first application, (iii) a study of the effect of vernatting which focuses on the behaviour of the main flavonoids in the leaves of red clover (T. pratense) under waterlogging conditions.