Essential Elements and Their Relations to Phenolic Compounds in Infusions of Medicinal Plants Acquired from Different European Regions

The aim of this research was to compare chemical composition of herbs acquired from different European countries. The concentrations of P, Fe, Mn, Zn, Cu, phenolic compounds, and the antioxidant activity were determined in infusions of 27 medicinal herbs (7 species) from Lithuania, Serbia, Italy, and Portugal. Total and extractable P were expressed in milligrams per liter and metals in micrograms per liter and followed the sequence: Fe > Mn > Zn > Cu, while antioxidant activity ranged from 29.4 to 217.8 mg of Trolox equivalent (TE) per liter. Total flavonoids were in the range of 20.5–95.1 mg L−1. The rank order of phenolic compounds assayed by HPLC method (in mg L−1 of infusion) was as follows: rutin > myricetin > quercetin > kaempferol, and chlorogenic > ferulic > p-coumaric > caffeic > gallic acids. Significant correlations were found between total P–inorganic phosphate P, Zn–Mn, Mn–Cu, total flavonoids–antioxidant activity, and quercetin with caffeic and ferulic acids. Generally, medicinal plant infusions differed in their chemical composition, strongly depending on plant species, regardless of the origin from distant geographical areas of Europe. Principal component analysis selected the concentrations of Cu, Mn, total and inorganic phosphate P, as factors which strongly influence differentiation of the samples. Moreover, infusions from Hyperici herba and Helichrysi inflorescentia contained significant amounts of water-extractable Mn and Fe forms as claimed by the Dietary Reference Intakes for humans.