Characterization of some potential medicinal plants from Central Europe by their antioxidant capacity and the presence of metal elements

Plants contain polyphenolic compounds such as phenolic acids, flavonoids, stilbenes, lignans, etc., which are endowed with antioxidant properties. The aim of this study was to correlate the total phenolic compound and flavonoid content of 15 medicinal plants with their antioxidant properties and to determine some important essential elements (Na, K, Ca, Mg, Zn, Se). The antioxidant capacity was tested by three methods (ABTS, DPPH, and FRAP) for the ability to provide electrons or hydrogen to various compounds, or to scavenge free radicals. The highest content of total phenolic compounds in aqueous extracts was found in Agrimonia eupatoria. In addition to this plant, high antioxidant capacities were also present in Origanum vulgare and Mentha × piperita. The positive correlation between the total phenolic compound content and the antioxidant capacity was strong, whereas flavonoids were correlated to antioxidant properties to a lesser extent. All the aqueous plant extracts contain larger amounts of potassium than sodium, which could be beneficial for humans with low NaCl diets. The significance of replenishing of calcium, magnesium, zinc, and selenium by drinking herbal teas is discussed.