The contribution of α-dicarbonyl compound dependent radical formation to the antiseptic effect of honey

Abstract Honey is known for its wound healing potential. In this study we investigated free radical formation and inhibition in different honeys and the influence on bacterial growth inhibition. α-Oxaldehydes and free amino acids were shown to be present in manuka and non-manuka honeys. With electron spin resonance we measured that methylglyoxal (MG) and glyoxal (GO) form different carbon centered radicals under the influence of either hydrogen peroxide or arginine and lysine. These radicals were also formed in a combination of α-oxaldehydes and amino acids in artificial honey, which was quantified by the cytochrome C assay. Also, a strong bactericidal activity for MG and GO (minimum concentration 0.6 and 1.25 mM) was shown against different bacterial strains. Interestingly, honeys with a high MG content were shown to be better free radical scavengers for hydroxyl and superoxide radicals, implying a complex mechanism for free radical donation and scavenging in honey.