Antioxidative properties of recently synthesised D-?-D type Schiff-base ligands

Two recently synthesised D-?-D type Schiff base ligands have been screened for their antioxidant capacity using several tests; reducing power, chelating ability on metal ions, scavenging capacity against the radicals 2,2-diphenyl-1-picrylhydrazyl, superoxide, hydroxyl, 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and N,N-dimethyl-p-phenylenediamine dihydrochloride. The results were compared with synthetic antioxidants e.g. butylated hydroxytoluene, butylated hydroxyanisole, ?-tocopherol, trolox or ascorbic acid. The results indicate that the ligands have significant hydroxyl and free radical scavenging activity, metal chelating effect and reducing power against various antioxidant systems in vitro. One ligand (L2) showed excellent activity on scavenging the ABTS radical and superoxide radical. Therefore, these ligands may be a new kind of effective scavengers of reactive oxygen species.