Hydroxyl radical scavenging effects of guaiacol used in traditional dental pulp sedation: Reaction kinetic study

Abstract

Guaiacol, which is a phenolic compound with a methoxy group and used in traditional dental pulp sedation, has the property of inducing cell proliferation. To clarify these mechanisms of guaiacol, this study examined the hydroxyl radical (•OH) scavenging effects of guaiacol in vitro. Generation of •OH was carried out by the Fenton reaction using mixture of ascorbic acid, H2O2, and Fe(III)-EDTA, and •OH was detected by measuring the •OH-mediated production of degradation products of deoxyribose, which reacts with 2-thiobarbituric acid (TBA) and is relatively stable for a long time. At concentrations of 10-10 M to 10-3 M, guaiacol inhibited the TBA reactive substance (TBA-RS) formation in a dose-dependent manner. Phenol and formaldehyde were also found to inhibit the TBA-RS formation, but their inhibitory activities were lower than that of guaiacol. The concentrations of guaiacol, phenol, and formaldehyde needed to cause 50% inhibition of TBA-RS formation were approximately 5 × 10-6, 5 × 10-5, and 2 × 10-3 M, respectively. In this reaction system, guaiacol showed no chelating reaction with ferrous ion and did not directly react with H2O2. Guaiacol also exhibited radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable free radical, but its scavenging activity was lower than that toward •OH. These results suggest that guaiacol is a potent scavenger of reactive oxygen radicals and that its radical scavenging activity may be associated with its effect on cell proliferation. Copyright © 2005 Biomedical Research Press.