Interaction of chlorogenic acid with model lipid membranes and its influence on antiradical activity.

Chlorogenic acid (CGA) is a strong phenolic antioxidant with antibacterial properties composed by a caffeoyl ester of quinic acid. Although a number of benefits has been reported and related to interactions with the red blood cell membranes, details on its membrane action and how composition and membrane state may affect it, is not yet well defined. In this work, the interaction of CGA with lipid monolayers and bilayers composed by 1,2-dimiristoyl-sn-glycero-3-phosphocholine (DMPC); 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (14:0 diether PC); 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-di-O-hexadecyl-sn-glycero-3-phosphocholine (16:0 diether PC) were studied at different surface pressures (π). The kinetics of interaction was found to be more rapid in DMPC than in the absence of carbonyl groups. Measurements by FTIR-ATR at different water activities confirm specific interactions of CGA with carbonyl and phosphate groups affecting water level along hydrocarbon region. The antioxidant activity of CGA in the presence of DMPC unilamellar vesicles, evidenced by the absorbance reduction of the radical cation ABTS•+, is significantly different with respect to aqueous solution. The influence of CGA on antiradical activity (ARA) with lipid membranes depending on the hydration state of the lipid interface is discussed.

Modulation of Interfacial Hydration by Carbonyl Groups in Lipid Membranes.

The lack of carbonyl groups and the presence of ether bonds give the lipid interphase a different water organization around the phosphate groups that affects the compressibility and electrical properties of lipid membranes. Generalized polarization of 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (14:0 diether PC) in correlation with Fourier transform infrared (FTIR) analysis indicates a higher level of polarizability of water molecules in the membrane phase around the phosphate groups both below and above Tm. This reorganization of water promotes a different response in compressibility and dipole moment of the interphase, which is related to different H bonding of water molecules with phosphates (PO) and carbonyl (CO) groups.