Phenolic Profile and Antioxidant Activity of Propolis Extracts From Poland

Propolis is a natural material collected by honeybees, containing bioactive compounds that exhibit biological activity. The aim of this study was to assess the chemical composition of Polish propolis extracted with two different concentrations of ethanol, namely 70% and 96%, and to evaluate their antioxidant activity depending on extraction conditions. Samples of Polish propolis were extracted with 70% and 96% ethanol in order to obtain the ethanolic propolis extracts EEP70 and EEP96, respectively. Concentrations of 10 flavonoids and 6 phenolic acids were determined using the UPLC-PDA-TQD system. The antioxidant properties were determined based on the DPPH· free radical scavenging activity, Fe3+ reducing power assay, and ferrous ions (Fe2+) chelating activity assays. Moreover, the effects of the propolis extracts on human red blood cell morphology , the selective permeability of their membrane, as well as on free radicals-induced hemolysis were also assessed. Qualitative and quantitative analyses of both propolis extracts indicated that 70% ethanolic extract contained higher amounts of phenolic compounds than 96% ethanolic extract. The levels of antioxidant activity indicated that both Polish propolis extracts exhibited a high and comparable antioxidant power. The concentration of ethanol used for extraction had no effect on the antioxidant potential of propolis. The presented results indicate that the extracts of Polish propolis are rich in phenolic compounds and are very effective as antioxidant agents. Therefore, they may be applied as a constituent of products used in phytotherapy regardless of the concentration of ethanol used in propolis extraction