Phytyl Phenolipids as Promising Biomembrane Antioxidants

Procedures for the easy preparation of a series of phytyl phenolipids were developed, yielding phytyl esters of caffeic, protocatechuic, homoprotocatechuic and dihydrocaffeic acids in high yields (70-95%). Preliminary characterization showed that these new compounds have a similar lipo-solubility and comparable radical scavenging capacity to that of the natural membrane antioxidant -tocopherol. Cyclic voltammetry analysis showed lower anodic peak potentials for the phytyl esters when compared with the parental phenolic acids and the electron transfer followed an ad-sorption-controlled mechanism. Despite having strong anti-radical capacity and of being able to penetrate the membrane, the antioxidant efficiency of phytyl esters in liposomal systems was deeply dependent on the structure of the phenolipid polyphenolic moiety. In the phosphatidyl-choline LUVs system tested, phytyl esters showed remarkable efficiency in preventing liposome autoxidation when compared to -tocopherol, excepted for the caffeic acid ester that did not show any improvement in the oxidative stability of liposomes. Nevertheless, as all the phytyl esters showed at least a similar activity when compared with -tocopherol, all these molecules can still be considered strong candidates for future interventions against oxidative stress in cells and lipo-proteins, deserving a proper evaluation of their antioxidant and anti-inflammatory capacity in cell models and in vivo.