Integration of (+)-catechin and β-sitosterol to achieve excellent radical-scavenging activity in emulsions

Novel amphiphilic antioxidant, (+)-catechin-β-sitosterol (CS), was designed and successfully prepared with integration of (+)-catechin and β-sitosterol through the linkage of succinic acid. Sequential esterification was carried out to connect (+)-catechin and β-sitosterol. The identity of CS was confirmed by NMR, IR and MS spectroscopies. DSC analysis revealed that ΔH of CS was much lower than those of (+)-catechin and β-sitosterol, indicating ameliorated crystallinity. The logP measurement demonstrated significantly increased lipophilicity. Then excellent antioxidant activities of the novel antioxidant in typical polyunsaturated lipid O/W and W/O emulsions were unveiled applying β-sitosterol bleaching assay and 5-dodecanoylaminofluorescein (DAF) fluorescent probe method. The antioxidative behavior of CS in emulsion was beyond the polar paradox hypothesis and could be rationalized by effective accumulation at oil/water interface owing to its amphiphilic nature. This study offers a promising solution for development of naturally derived amphiphilic antioxidants for lipid-based systems.