Proximate Composition and Antioxidant Activity of Selected Morphological Parts of Herbs

The aim of the study was to provide an analytical evaluation of the proximate composition, the total content of polyphenolic compounds and the antioxidant activity, of 27 selected plant materials collected in Poland (West Pomeranian). The basic chemical composition was determined in the ground samples according to the Association of Official Analytical Chemists methods. Antioxidant activity was tested using free radical methods ABTS^•+, DPPH^•+ and the FRAP method. The lowest concentration of dry matter (DM) was measured in black chokeberry (88.82 g/100 g) and the highest was found in milk thistle (94.65 g/100 g) as well as black cumin (95.09 g/100 g). The content of total polyphenols, assessed using the Folin–Ciocalteu method, ranged from 291.832–7565.426 mg of chlorogenic acid equivalent (CGA)/100 g of DM. Antioxidant activity measured sequentially against the radical ABTS^•+, DPPH^•+ and using the FRAP method was 26.334–1912.016 µM Trolox/g DM, 9.475–1061.068 µM Trolox/g DM and 26.252–1769.766 µM Trolox/g DM, respectively. The methanolic extract from milk thistle fruit in most assays was characterized by the lowest antioxidant activity and the lowest total content of polyphenolic compounds. Methanol extracts prepared from garlic, stinging nettle and cleavers showed the highest content of total polyphenols and antioxidant activity among the tested plant materials. The parts of plants with the highest antioxidant potential can be a source of new bioactive compounds, but further research is required to describe the profile of compounds harmful to human health.