P 061 - N,N.N′,N′-tetramethylhydroethidine (TMHE) - in search for better probes for the detection of superoxide radical anion

Abstract

The superoxide radical anion is an important reactive species produced by one-electron reduction of molecular oxygen. The main sources of superoxide radical anion in vivo are the enzymes NADPH oxidases (NOX) and mitochondria (mitochondrial electron transport chain). Superoxide radical anion reacts rapidly with nitric oxide with the formation of peroxynitrite (ONOO−). It can also undergo spontaneous or SOD-catalyzed dismutation with the formation of hydrogen peroxide (H2O2) and thus it is a precursor of other biologically relevant oxidants playing an important role in various pathologies. Due to its reactivity and short lifetime in vivo, its detection and quantitation is difficult and demands special and sensitive techniques. One of the approaches is the use of fluorogenic probes, the compounds which themselves are not fluorescent but in the reaction with superoxide are oxidized to the fluorescent products that can be directly detected. Among various profluorescent probes available hydroethidine (HE) seems to be a gold standard for detection of superoxide in biological systems. In the presence of superoxide radical anion, HE undergoes oxidative transformation into 2-hydroxyethidium (2-OH-E+), a specific marker of superoxide radical anion production. In the reaction with other radical, one-electron oxidants, HE is oxidatively transformed into ethidine and dimeric products. Here we present a spectroscopic and chemical characterization of new analogue of hydroethidine - N,N,N,N-tetramethylhydroethidine (TMHE).