Abstract
The aim of the study was to identify and determine the percent content of polyphenols in extracts from leaves and hawthorn bark, to examine the effect of the extracts on the properties of the biological membrane as well as to determine their antioxidant activity toward membrane lipids. In particular, a biophysical investigation was conducted on the effect of hawthorn extracts on the osmotic resistance and morphology of erythrocyte cells and on the packing of the heads of membrane lipids. Analysis of the polyphenol content of extracts used the HPLC method. Analysis of the polyphenol composition has shown a dominant share of procyanidins and epicatechin in both extracts. The research showed that the polyphenolic compounds contained in hawthorn extracts are incorporated mainly into the hydrophilic part of the erythrocyte membrane, inducing echinocyte shapes. They also diminish the packing order of the lipid polar heads of the membrane, as evidenced by the lowered generalized polarization values of Laurdan. The substances used induced increased osmotic pressure of erythrocytes, making them less sensitive to changes in osmotic pressure. The presence of the extract compounds in the outer hydrophilic part of the erythrocyte membrane, evidenced by examination of the shapes and packing in the hydrophilic part of membrane, indicates that the substances constitute a kind of barrier that protects the erythrocyte membrane against free radicals, while the membrane-bound extracts do not disturb the membrane structure and, thus, do not cause any side effects.