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 ( 1 O 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 1 mmol/L, nine prevented the degradation of deoxyribose induced by the Fenton reaction system (range 3–78%) or scavenged hydroxyl radicals (HO • ) directly (range 8–93%) and 14 showed the 1 O 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 1 O 2 directly, and consequently may be considered effective antioxidative agents. Copyright © 2007 John Wiley & Sons, Ltd.