Electron spin resonance spectroscopy of oxygen radicals generated by synthetic fecapentaene-12 and reduction of fecapentaene mutagenicity to Salmonella typhimurium by hydroxyl radical scavenging

Abstract

Fecapentaenes form a class of potent fecal mutagens and have been suggested to play an initiating role in colon carcinogenesis. Although several indications have been found that fecapentaenes may induce oxidative DNA damage as well as DNA alkylation, the mechanism of genotoxicity remains unknown. In this study, electron spin resonance spectroscopy with several spin traps has been used in order to determine whether reactive oxygen species can be formed by fecapentaene-12 (FP-12). No specific conditions could be defined that resulted in the direct formation of oxygen radicals from FP-12. However, peroxidation of FP-12 by various peroxidative enzymes has been shown to result in the formation of superoxide adducts of the spin traps alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Addition of superoxide dismutase resulted in a decreased spectrum intensity, whereas the hydroxyl radical scavenger t-butyl alcohol (tBA) appeared of no influence on the signal, both confirming the formation of superoxide. The formation of hydroxyl radical spin adducts has been demonstrated after peroxidation of FP-12 in incubations with the spin-trapping agent 2,2,6,6-tetramethyl-piperidine (TMP). Further, the effects of scavenging hydroxyl radicals with respect to the genotoxic potential of FP-12 in the Salmonella mutagenicity assay has been investigated. It was clearly shown that radical scavenging reduced the number of revertants in Salmonella strains TA100, TA102 and TA104. This mutagenicity-reducing effect was more convincing using both spin traps DMPO and TMP as compared to the effect of hydroxyl radical scavengers tBA and DMSO. Based on these findings, a reaction scheme is proposed that suggests the formation of superoxide after peroxidation of FP-12, which is subsequently converted to hydroxyl radicals by the iron-catalysed Haber-Weiss reaction.

Antioxidant Combination Inhibits Reactive Oxygen Species Mediated Damage

“…15,23) However, because of less pronounced antioxidant activity in vitro, they are considered not as effective as botanical antioxidants. 24,25) In general, the antioxidant activity of a naturally occurring antioxidant is measured as the scavenging capacity for free radicals, various procedures 17,[25][26][27] are used in the quantitative determination of antioxidant activity, but it is still unclear whether the antioxidant activity measured by these methods directly restrains the deleterious action of ROS, for example, fragmentation of proteins and DNA molecules. The antioxidant activity of naturally occurring antioxidants might be affected by the species of oxidative radicals used in quantitative examinations.…”

Commensal Bacteria, Redox Stress, and Colorectal Cancer: Mechanisms and Models

“…The mechanisms for genotoxicity are unknown, but some evidence indicates oxidative damage to DNA can occur through radical mechanisms. Peroxidation by COX isoforms can also generate hydroxyl radical when iron is available as a catalyst (117,118). Target cells with high concentrations of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxo-dG), a marker for oxidatively damaged DNA, support this hypothesis (119).…”

Comparing TiO2 photocatalysis and UV-C radiation for inactivation and mutant formation of Salmonella typhimurium TA102

“…Despite the lack of work available in scientific literature concerning the effect of TiO2 photocatalytic process on the formation of mutants in Salmonella strains, the possible role of hydroxyl radicals has been investigated (Kanno et al 2012). De Kok et al (1992 used electron spin resonance (ESR) spectroscopy to detect and identify oxygen species generated by fecapentaenes (potent genotoxins found in human feces) and investigated the influence of scavenging reactive oxygen species (dimethyl sulfoxide (DMSO), t-butyl alcohol, t-butyl hydroperoxide (TBOOH), 2,2,6,6-tetramethylpiperidine and 5,5-dimethyl-lpyrroline-A'-oxide) on the mutagenicity of Salmonella strains including TA102.…”