Abstract
A series of guanidines and their copper (II) complexes were investigated for their radical scavenging activity including peroxyl radicals (ROO center dot), superoxide anion (O-2(center dot-)), hydroxyl (center dot OH), and reactive hydrogen peroxide (H2O2) species. Among the Cu(II) complexes, Cu-MR-9-2 shows the highest, Cu-MR-9-3, Cu-MR-9-6 less and Cu-MR-9-1 least antioxidant potential. The Cu(II) complexes show better Fe2--chelating activity than that of ligands. Among the Cu(II) complexes Cu-MR-9-2 was found to have the highest, Cu-MR-9-6 moderate, MR-9-3 less and Cu-MR-9-1 least ferric reducing capacity. The IC50 values for ligands (MR-9-1, MR-9-2, MR-9-3, MR-9-6) were determined to be 197.53 +/- 7.13, 189.07 +/- 7.34, 207.98 +/- 6.78 and 233.38 +/- 6.37 mu M, which showed lower antioxidant activity than their Cu(II) complexes. The IC50 values for ascorbic acid were found to be 51.60 +/- 13.18 mu M. The Cu(II) metal compounds (Cu-MR-9-1,Cu-MR-9-2, Cu-MR-9-3 and Cu-MR-9-6) were detected to be the most powerful scavengers of the hydroxyl radical with IC50 up to 108.03 +/- 11.34 mu M, 101.41 +/- 12.10 mu M, 90.59 +/- 11.53 mu M and 88.86 +/- 13.16 mu M, respectively.