The antibacterial properties of honey

Abstract

Honey has been used medicinally by man for thousands of years. With the apparent misuse of many antibiotics there has recently been renewed interest in such natural antibacterial substances. Honey is known to contain several natural antibiotic systems but research so far has been largely confined to the glucose oxidase (inhibine) area. Some past research, however, has indicated the possible existence of anti­bacterial substances other than hydrogen peroxide (inhibine) and the osmotic potential of honey. The aim of this project was to confirm the existence of these substances and to isolate and characterise them if possible. The antibacterial assay used to detect activity was an agar diffusion technique incorporating staphylococcus aureus. Various honey samples were screened for non-peroxide antibacterial activity and the most active honey (manuka) selected for further investigation. The activity was found to be completely heat-stable (1 hr, 95 °C) at acidic pH but less stable at neutral pH, and the honey was less active at neutral pH. Solvent extraction of the honey was carried out with ethanol, and ether was added to precipitate most of the sugar. All activity was recovered from the honey into the extract in this way. Further isolation of the active fractions was carried out using preparative thin-layer chromatography. Information on the fractions with activity that were isolated was obtained by ultraviolet spectroscopy, infra­red spectroscopy, nuclear magnetic resonance and mass spectrometry.