Interactions of cyanidin and cyanidin 3-O-β-glucopyranoside with model lipid membranes

Abstract

Cyanidin and cyanidin 3-O-β-glucopyranoside (Cy3Glc) are flavonoids that have several biological properties, including as antioxidants. The interactions of cyanidin and Cy3Glc with model lipid membranes differing in surface charge and phase state were investigated using differential scanning calorimetry and fluorescence emission polarization spectrometry. Differential scanning calorimetry shows that cyanidin and Cy3Glc have no effects on the phase transition of zwitterionic liposomes composed of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and negatively charged liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) at pH 7.0. Emission polarization spectrometry using 1,6-diphenyl-1,3,5-hexatriene (DPH) and N,N,N-trimethyl-4-(6-phenyl-1,3,5-hexatrien-1-yl)phenylammonium p-toluenesulfonate (TMA-DPH) probes shows that cyanidin slightly increases the polarization of DPPC and DPPG liposomes in the gel state at 298.15 K. Significant ordering effects of cyanidin on DPPC liposomes in the liquid state at 318.15 K and no effect on the liquid state of DPPG at 318.15 K were observed using the DPH and TMA-DPH probes. Cy3Glc causes no change in polarization regardless the gel or liquid-disordered state of DPPC or DPPG liposomes. Cy3Glc due to its glucoside moiety is too bulky to partition into water–lipid interface or between the nonpolar acyl chains of membranes. The results of this work may contribute to understanding the low bioavailability of glycosides.