A research team at the Institute of Food Chemistry, Technical University of Dresden, "unambiguously demonstrates for the first time that Methylglyoxal is directly responsible for the antibacterial activity of Manuka honey."
Prof Henle notes the high amounts of Methylglyoxal found in Manuka honey have not yet been found in any other food.
Methylglyoxal levels in the Manuka honeys were up to 1000-fold higher than in the non-Manuka products. 

The discovery of methylglyoxal in manuka honey creates the opportunity for further research into how it forms in the honey, and to understand better its role in nutrition, wound healing and for immune system protection.