Antibacterial activity and physico-chemical analysis of several types of honey with different floral origins in the Golestan province

Study in order to introduce new antimicrobial agents with natural origin to prevent the antibiotic resistance and eliminating its effects, employing chemical agents is an indispensable necessity. Honey, as an important food with natural origin has high antimicrobial potential. Several factors have contributed to the antibacterial activity of honey. For example, acidity, osmolarity, hydrogen peroxide, phenolic and flavonoid compounds, including these factors. Also, small amounts of glucose oxidase, protease, amylase, catalase and phosphatase enzymes and chemical compounds such as methylglyoxal are also effective. Floral origin of honey is effective on its biological properties including antimicrobial, anti-tumor, anti-inflammatory, antioxidant and antiviral activity. So this study was done to evaluate the antibacterial activity and physico-chemical analysis of four types of honey with different floral origin including: Thyme, Eryngium, Pennyroyal and Dill collected from the bee hives in Golestan province.
Four honey samples with different floral origin including, Thyme, Eryngium, Pennyroyal and Dill were collected from the bee hive in the Golestan province in north of Iran. The bacterial strains used in this study, including two species of gram-negative of Escherichia coli and Shigella dysenteriae and the two species of gram-positive of Staphylococcus aureus and Bacillus cereus were provided in lyophilized. Bacterial strains in BHI broth were activated and from each of them were prepared bacterial suspensions equivalent to the McFarland 0.5 turbidity standard (1.5×108 CFU/ml). Evaluation of antibacterial activity using agar well diffusion method was performed. For this purpose serial dilutions of honey samples were prepared aseptically in sterilized distilled water. Surface of Mueller Hinton agar were uniformly inoculated with bacterial suspension containing of 1.5×108 CFU/ml. Then wells of 8 mm in diameter were prepared and these wells were filled with different dilutions of honey samples. After incubation at 37°C for 24 h, antibacterial activity was analyzed by measuring the zones of inhibition. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of honey samples were determined by using broth macro-dilution method. For this purpose, each of the tubes from different dilutions of honey samples were added by 5×105 CFU/ml from each of the tested bacteria and incubated for 24 h at 37°C. The results for microbial turbidity of visible were recorded. The last dilution (lowest concentration) in which microbial turbidity was not observed, as the MIC was considered. For the determination of MBC, from the tube that contained honey concentrations higher than the MIC were cultured onto the agar medium. The MBC was defined as the lowest concentration that allowed no visible growth on the agar. Also the studied physico-chemical properties were moisture content, pH, acidity, ash content and reducing sugars that was performed according to the Iranian National Standard No. 92.
The results indicated that the antibacterial effects of the tested honeys, and the difference between floral origins honeys is effective in antibacterial properties. MIC and MBC values obtained for the tested honeys were in the range of %6.25-50% (vol/vol). Highest antibacterial activity was recorded for Eryngium honey by agar well diffusion method with zone of inhibition of 15.5, 14,11 and 11 mm against S. dysenteriae, S. aureus, B. cereus and E. coli at concentration of 50% v/v respectively and its MIC for this bacteria were, 6.25%, 10%, 10% and 25% respectively. also low antibacterial activity of Pennyroyal honey was confirmed so that MIC of the this honey for E. coli, S. aureus, B. cereus and S.dysenteriae was, 50%, 25%, 12.5% and 10%, respectively. The quality of honey depends on a number of physico-chemical properties such as moisture, ash content, pH, acidity, the amount of sugars. For this reason, standards for honey have been set by different countries. The physico-chemical analysis of honeys showed moisture contents in the range of 22.56-25.36%, acidity in the range of 12.58-13.59 meq/kg, pH in the range of 4.15-4.26, reducing sugars in the range of 63.7-63.8%. Also the ash content of Eryngium honey with 0.183% was higher than the other honey samples. This higher level might be due to the higher pollen count in this region. High ash contents may also depend upon the floral origin of honey and the material collected by bees during foraging. The low acidity of honey samples studied in the present study was due to the fact that there was no unwanted fermentation in these samples. Overall, the results implied that honey samples with different floral origin collected from the bee hive in the Golestan province in north of Iran have variable potential antibacterial activity. The variety of antibacterial effects of different types of honey can be due to differences in plants that honey is obtained from. In other words, different species of plants in different regions have different compounds and their obtained honey will not be the similar and thus its biological effects also will be different.