Antioxidant activity of hydroxytyrosyl esters studied in liposome models

摘要

Abstract The properties and the antioxidant activity of a series of hydroxytyrosyl esters having different carbon chain lengths (C4, C8, C12 and C18) have been measured in phosphatidylcholine model membrane (liposomes) using specific probes for the bilayer and liposome lumen microenvironment, i.e., 1,6-diphenyl-1,3,5-hexatriene (DPH) and 2′,7′-dichlorodihydrofluorescein (H 2 DCF), respectively. Antioxidants self-assembly and their interaction with liposomes has been evaluated by light scattering, fluorescence, turbidimetry, gel filtration chromatography and microfiltration measurements, allowing the determination of critical aggregation concentration, bound fraction, capacity of crossing the lipid bilayer. The distribution of hydroxytyrosyl long chain esters has been proved to depend quite specifically on their lipophilic chain length, and this turns to have deep effects on their antioxidant behaviour. Shedding new light on the cut off effect and antioxidant behaviour of phenolipids, this study also put forward the relevance of cell-free liposome-based cellular models, like giant liposomes, for further characterization of analogous systems. Graphical abstract Display Omitted Highlights ? C4- C8- C12- C18-hydroxytyrosyl esters have been tested in vitro as antioxidants. ? Their binding and penetration inside POPC liposomes are chain length-dependent. ? Antioxidant activity is evaluated with membrane-soluble and water-soluble probes. ? Giant lipid vesicles allow direct examination of antioxidant activity. ? Different hydroxytyrosyl esters perform differently depending on their location.