Investigating the Molecular Effects of Curcumin by Using Model Membranes

Curcumin (diferuloylmethane, CUR), is an potential agent that is extracted from the rootstalk of the Curcuma longa (turmeric) plant and has anti-cancer effects as well as antibiotic, antiviral, antifungal and anti-inflammatory properties. Within the scope of this study, it was aimed to examine the molecular interactions of curcumin with model membranes. The model membranes were prepared in the form of multilamellar vesicles (MLVs) by using cholesterol (CHOL), one of the most important components of biological membranes, and dipalmitoyl phosphatidylcholine (DPPC), one of the most frequently observed phospholipids in biological membranes. The effects of curcumin were investigated on lipid bilayers, which were classified as binary (DPPC +CUR) and ternary (DPPC/CHOL +CUR) systems. The effects of curcumin at different concentrations on the model membranes were examined with the differential scanning calorimetry (DSC) and Fourier transformation infrared (FTIR) spectroscopy techniques. The results obtained from the DSC indicated that the use of the agent and the cholesterol with the agent caused the pretransition temperature to disappear both in the binary and ternary systems. While the presence of curcumin at different concentrations caused a decrease in the main phase transition temperature (T-m) and enthalpy (Delta H) values in both systems, it caused an increase in the width of the transition at half peak height (Delta T-1/2). The results obtained from the FTIR analyses indicated that while the existence of curcumin and cholesterol with curcumin decreased the order of model membranes in the gel phase, it increased it in the liquid crystalline phase and it also caused an increase in fluidity in both phases. When the C = O stretching bands were examined, an increase in the wavenumbers was observed in both phases of both systems. According to the results of the analysis of the PO2- stretching bands, there was an increase in the wavenumbers of samples with 24% mol curcumin in the binary system in both phases and a decrease in the wavenumbers of samples of other concentrations. In the ternary system, an increase was observed in wavenumbers in all concentrations in both phases. When all of the calorimetric and spectroscopic results were evaluated, it was determined that curcumin interacts with the lipids as a whole.