Antimicrobial activity of honey extracts against Escherichia coli

MARIA FLORENCIA FANGIO; MIRIAM OFELIA IURLINA; ROSALÍA FRITZ

Ciudad Autónoma de Buenos Aires

Congreso; Congreso Internacional Apimondia 2011; 2011

SADA y APIMONDIA

The growth of many microorganisms associated with diseases and food spoilage is inhibited by honeys. The antibacterial properties of honey are due to hydrogen peroxide, osmotic effect of its high sugar content and some honeys have an additional phytochemical antibacterial compounds. The nature of these chemicals and the mechanisms of their action are not fully understood. Some works attempted to determine the fraction of the honey that contains the non-peroxide activity. The aim of the present work was to characterize honeys collected from Buenos Aires province and to evaluate the inhibitory activity of their extracts on Escherichia coli growth. Sensory and physicochemical characterization of honeys was evaluated; the colour of honey was measured by spectrophotometric method. Moisture content was determined through the refractive index of honey. Acidity content and qualitative determination of diastase and glucose-oxidase activity was performed with the method suggested by Bianchi (1984). Extraction was carried out by column chromatography using Amberlite XAD-4 resin. Antimicrobial activity of raw honey and extracts was evaluated by serial dilution test. Physicochemical parameters such as colour, free acidity, pH and moisture showed that the last one reflected significant differences between honeys. None of the extracts of acidified water showed antimicrobial effect to the concentrations of the extracts used. Both methanolic and aqueous extracts showed higher antimicrobial activity than raw honeys. The most active antimicrobial honeys showed higher activity of methanol extracts (Minimum Inhibitory Concentration (MIC):1,23 % (w/v) and: Minimum Bactericidal Concentration (MBC): 3,3 % (w/v) than honeys with lower activity (MIC: 4,7 % (w/v) and MBC: 5 % (w/v). The aqueous extracts of the honeys with higher antimicrobial activity showed lower antimicrobial effect than the extracts of other honeys. The results of this work suggest that some components extracted with methanol would be associated to honeys with the additional phytochemical antimicrobial activity.