HPLC with electrochemical detection of metal-flavonoid-complexes isolated from food

Summary The electrochemical and chromatographic behaviour of flavonoid standards and of flavonoids extracted from food (green tea, black tea and onions) is investigated with respect to metalbinding properties. It is shown that metals such as iron, copper or aluminium are complexed by flavonoids, preferrably by those having an aromatic o-dihydroxy structure. This is confirmed by cyclic voltammetry on HPLC fractions (stopped flow) and by AAS measurement of metals. As the complexing sites of flavonoids are closely related to electrochemical properties, this is used for an indirect detection of metal species at low oxidation potentials. For iron species in particular a sensitive and selective detection is possible. For copper reductive detection can also be used.