Nature and origin of the antibacterial substances in honey

The nonperoxide antibacterial activity of honey and honey fractions was tested with Staphylococcus aureus and Micrococcus luteus bacterial species. Antibacterial activity correlated significantly with the honey acidity but did not correlate with honey pH. There were small differences between the antibacterial activities of different honey types: rhododendron, eucalyptus and orange honeys had a relatively low activity, whereas dandelion, honeydew and rape honeys had a relatively higher activity. These results suggest that a part of the antibacterial activity might be of plant origin. However, the antibacterial activity of sugar-adulterated honeys was the same as that of control honeydew honeys produced in the same apiary suggesting that the major part of the antibacterial activity of honeydew honey is of bee origin. Ten different honeys were fractionated into four fractions wing column chromatography or vacuum distillation: acidic; basic; nonvolatile, nonpolar; and volatile. The antibacterial activity of the different fractions tested was: acids > bases = nonpolar nonvolatiles > volatiles. This order was the same using either Staph. aureus or Micrococcus luteus as test strains. An exception was manuka honey from New Zealand where almost the entire activity was found in the acidic fraction. (C) 1997 Academic Press Limited.