COMPARISON OF ANTIOXIDANT ACTIVITIES OF AMINOGUANIDINE, METHYLGUANIDINE AND GUANIDINE BY LUMINOL-ENHANCED CHEMILUMINESCENCE

1 The objective of this study was to investigate the ability of aminog uanidine, methylguanidine and guanidine to inhibit free radicals or me tabolites generated by either stimulated human leucocytes or cell-free systems using luminol-enhanced chemiluminescence (CL). 2 Aminoguanidi ne (0.1 mu M-10 mM), methylguanidine (10 mu M-10 mM) and guanidine (10 mu M-10 mM) produced concentration-dependent inhibition (96 +/- 0.1%, n=7, 59 +/- 1.3%, n=6, and 62 +/- 3%, n=6, P<0.05 at 10 mM, respectiv ely) in FMLP-stimulated leucocytes CL. 3 In cell-free experiments, hyd rogen peroxide (H2O2), hypochlorous acid (HOCl), hydroxyl radical and peroxynitrite-induced CL responses were initiated by hydrogen peroxide (3.5 mM), NaOCl (50 mu M), FeSO4 (40 nM) and peroxynitrite (20 nM), r espectively. Aminoguanidine, methylguanidine and guanidine produced co ncentration-dependent inhibition in H2O2-(69 +/- 0.7%, n=7, 26 +/- 1%, n=6, and 15 +/- 0.5%, n=6, at 1 mM, respectively) and HOCl-(84 +/- 0. 3%, n=6, 50 +/- 1%, n=6, and 29 +/- 1%, n=7, at 1 mM, respectively) in duced luminol CL. Peroxynitrite-induced CL was markedly attenuated in a concentration-dependent manner by aminoguanidine (99 +/- 0.1%, n = 6 , at 10 mM), methylguanidine (5 +/- 0.2%, n = 6, at 10 mM) and guanidi ne (27 +/- 0.4%, n=7, at 10 mM). However, inhibition with aminoguanidi ne was found to be more marked than with methylguanidine and guanidine . Aminoguanidine (95 +/- 0.5%, n = 6, at 1 mM) and methylguanidine (25 +/- 1%, n=6, at 1 mM), but not guanidine (2 +/- 1%, n=6, at 1 mM), si gnificantly decreased ferrous iron-induced CL. 4 Collectively, these d ata suggest that aminoguanidine and a high concentration (greater than or equal to 0.1 mM) of methylguanidine have direct scavenging activit ies against H2O2, HOCl, hydroxyl radical and peroxynitrite. Guanidine, at a high concentration (greater than or equal to 0.1 mM), scavenges H2O2, HOCl and peroxynitrite, but not the hydroxyl radical. These dire ct scavenging properties may contribute to inhibitory effects of these compounds on human leucocyte CL.