Structure influence on biophenols solubility in model biomembranes detected by differential scanning calorimetry

The protective effects of some foods, in particular fruits and vegetables, against cardiovascular disease and cancer are believed to be due to the presence of antioxidant substances such as hydroxyaromatic compounds. The aim of this work was to study (i) the interaction of three biophenols derived from benzoic acid (p-hydroxybenzoic acid, vanillic acid, syringic acid and benzoic acid) with model biomembranes and (ii) their transfer through an aqueous medium to be absorbed into a lipid bilayer, investigating the effect they exert on the thermotropic behaviour of model membranes represented by dimyristoylphosphatidylcholine multilamellar vesicles using differential scanning calorimetry. The compounds, when dispersed in liposomes during their preparation, at pH = 4, were found to modify the gel to liquid crystal phase transition of the lipid vesicles, causing a temperature shift towards lower values. The temperature shift was a function of the concentration of acids in the lipid aqueous dispersions and their lipophilic character. The kinetic experiments of compounds transfer through the aqueous medium and the absorption by the bilayer were performed contacting the antioxidant compounds (at a fixed concentration) and the model membrane at increasing incubation times. These experiments reveal that the transfer of the examined compounds through the aqueous medium and their uptake by bilayer are influenced by the presence of substituents located on the ring, which should consequently modify their lipophilicity.