In vitro scavenging activity for reactive oxygen species by N-substituted indole-2-carboxylic acid esters

The hydroxyl radical (HO.)- and superoxide anion radical (O-2(.))-scavenging activity, as well as the singlet oxygen (O-1(2))-quenching property of N-substituted indole-2-carboxylic acid esters (INDs) were investigated by deoxyribose degradation assay, a chemiluminescence method and the electron spin resonance (ESR) spin-trapping technique. This novel group of compounds was developed as a search for cyclooxygenase-2 (COX-2)-selective enzyme inhibitors. The results obtained demonstrated that of the 16 compounds examined, five inhibited light emission from the superoxide anion radical (O-2(.))-DMSO system by at least 60% at a concentration of I mmol/L, nine prevented the degradation of deoxyribose induced by the Fenton reaction system (range 3-78%) or scavenged hydroxyl radicals (HO center dot) directly (range 8-93%) and 14 showed the O-1(2)-quenching effect (range 10-74%). These results indicate that majority of the indole esters tested possess the ability to scavenge O-2(-), and HO radicals and to quench O-1(2), directly, and consequently may be considered effective antioxidative agents. Copyright (C) 2007 John Wiley & Sons, Ltd.