Effects of brewing time on the content of minerals in infusions of medicinal herbs

The aim of this study was to analyze the influence of brewing time on the content of select trace elements (Cu, Zn, Fe, Mn) and heavy metals (Pb, Cd) in homogeneous and mixed herbs used in therapy of digestive system diseases and in regulation of digestive processes. The study involved 10 types of preparations of herbal teas (mono- and multi-component sachets) acting on the gastrointestinal tract and digestive processes. Also, four types of black teas were examined for comparison. Aqueous extracts were made from each sample. As the manufacturers recommend herbal teas to be brewed for 5-15 min, in our study analyses were carried out for aqueous extracts brewed for 5 and 10 min. Contents of minerals in dry matter of the analyzed herbal and black teas and herbal blends were very differentiated, which could be due to species diversity and origin of the raw material. The brewing time had no significant effect on the percentage of the analyzed microelements extraction to the aqueous phase, however in the case of copper, manganese and lead the longer time of extraction resulted in a reduced yield of this process. An opposite dependency was noted in the case of iron, cadmium, and zinc.