The formation of pyrazine cation radicals was detected in model systems consisted of D-(+)-glucose (1.0 mol L^-1) and structural isomers of aminobutanoic acid (1.0 mol L^-1) heated at the temperature of 98 °C for 20 minutes using electron spin resonance (ESR) spectrometry. Based on the analyses of hyperfine structure of ESR spectra of reaction mixtures of model systems, the presence of 1,4-disubstituted pyrazine cation radicals was found. Different polyphenols (gallic, caffeic, ferulic, chlorogenic acid, and tannic acid) were added in the model systems to investigate their influence on the formation of pyrazine cation radicals. It was found that tannic acid was the most efficient in inhibiting the formation of free radicals followed by gallic > caffeic ³ chlorogenic > ferulic acid.