Anti-bacterial properties of selected honey samples

Abstract

The composition, taste and color of different honey are determined by the type of flower source, the geographical area, the climate, and the different species of bees involved in honey production, which is also conditioned by the processing techniques and storage. This study aims at screening a variety of honey samples for anti-bacterial properties against some gram-positive and gram-negative bacteria using agar well diffusion method. The anti-bacterial activity of this study demonstrated varied degree of inhibitory effects against the growth of three gram-positive and three gram-negative bacteria. The gram-positive bacteria used for the study were S. aureus, L. monocytogenes and B. cereus while the gram-negative bacteria used were E. coli, P. aeruginosa and S. marcescens. The anti-bacterial activity shows that honey sample A was effective against the growth of E. coli (13.00 ± 1.41mm) and S. aureus (8.50 ± 0.71mm) only at 100 mg/ml. Honey samples B, C, D and E showed no inhibition against any of the bacteria. Honey sample F was effective against the growth of E. coli (12.00 ± 1.41mm) only. Honey sample G inhibited the growth of E. coli, P. aeruginosa, L. monocytogenes and S. aureus and was further used for bacteriostatic and bactericidal analysis. Honey sample H was effective against the growth of E. coli only across three concentrations. The result from honey sample I showed inhibition against the growth of E. coli, P. aeruginosa and S. marcescens only with the highest inhibition against the growth of E. coli (19.50 ± 2.12 mg/ml) followed by S. marcescens (15.50 ± 4.95 mg/ml) and lastly, P. aeruginosa (13.00 ± 0.00 mg/ml). Honey sample J was effective against the growth of E. coli (15.50 ± 0.71 mg/ml), P. aeruginosa (14.00 ± 2.83 mg/ml), L. monocytogenes (14.50 ± 0.71 mg/ml) and S. marcescens (15.00 ± 1.41 mg/ml). Honey sample K was effective against the activity of E. coli (14.50 ± 3.54 mg/ml), P. aeruginosa (12.00 ± 1.41 mg/ml), S. aureus (13.00 ± 4.24 mg/ml) and S. marcescens (17.50 ± 2.12 mg/ml). Comparisons across the concentrations were analyzed and the results showed the different levels of zones of inhibition against the tested organisms. None of the honey samples was effective against the activity of Bacillus cereus. The minimum inhibitory concentration (MIC) of honey samples G, H, I, J and K against E. coli, P. aeruginosa, S. aureus, L. monocytogenes and S. marcescens shows that the MIC ranged from 12.5 mg/ml to 100 mg/ml. The minimum bacteriocidal concentration (MBC) showed that the honey samples had no bactericidal effect on the tested bacteria. The quantitative phytochemical analysis on total phenolics and flavonoid revealed the presence of phenols and flavonoid. Total phenol ranged from 47.62 mg/ml to 161.34 mg/ml while the total flavonoid ranged from 0.095 mg/ml to 0.395 mg/ml. The hydoxymethylfufural (HMF) level result which is a test for quality showed that the HMF levels of the honey samples used in the study are very low with the values ranging from 0.455 mg/ml to 2.187 mg/ml. This study concludes that the honey samples used for the study were of high quality and contain anti-bacterial properties which could be as result of the antioxidant effect of the phenol present in the honey samples and hence this confirms that honey can be used in treatment of bacterial infection and reduction of oxidative stress.