(±)-Catechin—A Mass-Spectrometry-Based Exploration Coordination Complex Formation with Fe(II) and Fe(III)

Catechin is an extensively investigated plant flavan-3-ol with a beneficial impact on human health that is often associated with antioxidant activities and iron coordination complex formation. The aim of this study was to explore these properties with Fe(II) and Fe(III) using a combination of nanoelectrospray-mass spectrometry, differential pulse voltammetry, site-specific deoxyribose degradation assay, Fe(II) autoxidation assay, and brine shrimp mortality assay. Catechin primarily favored coordination complex formation with Fe ions of the stoichiometry catechin:Fe in the ratio of 1:1 or 2:1. In the detected Fe–catechin coordination complexes, Fe(II) prevailed. Differential pulse voltammetry, the site-specific deoxyribose degradation, and Fe(II) autoxidation assays proved that coordination complex formation affected catechin’s antioxidant effects. In situ formed Fe–catechin coordination complexes showed no toxic activities in the brine shrimp mortality assay. In summary, catechin has properties for the possible treatment of pathological processes associated with ageing and degeneration, such as Alzheimer’s and Parkinson’s diseases.