The aim of the study was to determine changes incurred in lipid model membranes by polyphenol compounds from blueberry fruit of the genus Vaccinium that includes low, high and black blueberry. In particular, the effect of extracts on the packing order in the lipid hydrophilic phase, the fluidity of the hydrophobic phase, as well as the temperature of the phase transition in phospholipids was studied. Model membranes were formed of dipalmitoylphosphatidylcholine (DPPC) and egg phosphatidylcholine. The interaction of extracts with lipids was studied using the differential scanning calorimetry, infrared spectroscopy (ATR-FTIR) and fluorimetry using Laurdan, Prodan and DPH probes. All experimental results indicate that the biggest changes are in the hydrophilic part of the lipid bilayer. The polyphenol compounds had practically no influence on fluidity in the hydrophobic region of the membranes. No changes in the temperature of the main phase transition of DPPC were observed and only a small change in the temperature of pretransition for high concentration of compounds. Results obtained with the ATR-FTIR method did not reveal any changes in the alkyl chain region of bilayer; however, a small shift of bands was observed for phosphate and choline groups-the broadest effect appeared for the wild bilberry. The findings indicate that polyphenolic compounds contained in extracts of blueberries interact with the membrane surface and therefore can protect it.
