Antimicrobial activity of methylglyoxal, a phytochemical found in some types of honey, against pathogenic bacteria

Recent evidence suggests that methylglyoxal (MG), a highly reactive ketoaldehyde, is the main responsible for the unusually high antimicrobial activity of some New Zealand honeys. To provide further support to this hypothesis and assess the potential of MG as a new natural antimicrobial agent, we performed comparative in-vitro activity tests on some of the microorganisms most frequently associated with human infections, including amethicillin-resistant Staphylococcus epidermidis (MRSE) strain froma clinical isolate.Very similar activity profileswere observed by using MG or amedical-grade (UMF 25+)Manuka honey as antimicrobial agents, with the following susceptibility order: MRSE, S. aureus > E. coli, P. mirabilis > P. aeruginosa. MG exhibited bacteriostatic and bactericidal activity against all the microorganisms tested, with MIC and MBC values ranging from1.05 to 4.22mMand 2.11 to 4.22mM, respectively.Experiments made by adding 70mMMGto an artificial honey and an equimolar glucose fructose mixture showed that the activity ofManuka honey arises primarily fromthe presence of high levels ofMG.The remarkable antibacterial potency of MG makes it an attractive candidate for the development of pharmaceutical compositions for the treatment of microbial infections.