Effect of hydrogenated cardanol on the structure of model membranes studied by EPR and NMR.

Hydrogenated cardanol (HC) is known to act as an antiobesity, promising antioxidant, and eco-friendly brominating agent. In this respect, it is important to find the way to transport and protect HC into the body; a micellar structure works as the simplest membrane model and may be considered a suitable biocarrier for HC. Therefore, it is useful to analyze the impact of HC in the micellar structure and properties. This study reports a computer aided electron paramagnetic resonance (EPR) and (1)H NMR investigation of structural variations of cetyltrimetylammonium bromide (CTAB) micelles upon insertion of HC at different concentrations and pH variations. Surfactant spin probes inserted in the micelles allowed us to get information on the structure and dynamics of the micelles and the interactions between HC and CTAB. The formation of highly packed HC-CTAB mixed micelles were favored by the occurrence of both hydrophobic (chain-chain) and hydrophilic (between the polar and charged lipid heads) interactions. These interactions were enhanced by neutralization of the acidic HC heads. Different HC localizations into the micelles and micellar structures were identified by changing HC/CTAB relative concentrations and pH. The increase in HC concentration generated mixed micelles characterized by an increased surfactant packing. These results suggested a rod-like shape of the mixed micelles. The increase in pH promoted the insertion of deprotonated HC into less packed micelles, favored by the electrostatic head-head interactions between CTAB and deprotonated-HC surfactants.