Effect of Hydrophobic Chain Length on the Antioxidation Properties of Alanyl Tyrosine Dipeptide-type Surfactants

The antioxidant (AOX) activities of alanyl tyrosine dipeptide-type surfactants with several chain lengths were investigated. The critical micelle concentration decreased exponentially with the carbon number of the hydrophobic chain of the surfactant. The antioxidative property was investigated using the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid ammonium salt) (ABTS) assay and the oxygen radical absorbance capacity (ORAC) assay. The AOX activity was found to be strongly dependent on the chain length in the monomer solution. Therefore, an increase in the molecular size negatively influenced the AOX ability of the tyrosine residue. However, it was almost independent of the chain length of the surfactant in the micellar solution. The micelle particles acted as a catalyst for the reduction of the radicals in the ORAC assay.