Determination of magnesium, manganese, copper and zinc in infusions of inflorescences and leaves of Solidago canadensis

The Solidago canadensis (Canada goldenrod) species is an invasive plant in Europe and Asia. It grows mainly in anthropogenic environments, including those with a high content of heavy metals in soil. Goldenrod is also a honey plant, and its inflorescences and leaves are used in herbal medicine. The aim of the study was to determine the content of metals: Mg, Mn, Cu and Zn, in inflorescences and leaves of S. canadensis and in water extracts prepared from them. Material for the research was obtained in Poland. The content of the metals was determined by atomic absorption spectrometry. It was found that leaves of S. canadensis contained more Mg and Zn, but less Cu compared with inflorescences. The content of the metals in water extracts was proportional to their content in the raw material, except the content of Mn in leaves. Among the metals studied, the highest extraction of Cu and Mg was noted in infusions of leaves and inflorescences, while Zn achieved the highest extraction in infusions of inflorescences. Mn was extracted to the least extent both in leaves and inflorescence infusions. Infusions of goldenrod leaves provided similar amounts of Mg, Cu and Zn as tea infusions. Infusions of inflorescences provided more Cu and Zn than infusions of chamomile flowers. Considering the use of S. canadensis in phytotherapy, water extracts from goldenrod leaves and inflorescences had a negligible share of the analysed metals (on average about 1% or less) in the recommended daily allowances (RDAs).