**5. Conclusions**

In conclusion, analysis of the antibacterial activity of commercial honeys purchased in Slovakia revealed that more than 40% of the samples tested exhibited low antibacterial activity, identical to that of artificial honey (sugars only). There was a significant correlation between the overall antibacterial activity and H2O2 content of honey samples. However, in some cases, honey samples exhibited high antibacterial activity while generating low levels of H2O2 and vice versa. Honey samples from local beekeepers showed superior antibacterial activity compared to medical-grade honeys which are recommended for the treatment of infected wounds. The antibacterial activity of honey, as one of its well-described biological properties, should be used as an additional quality standard reflecting its biological properties. Further studies are needed to characterise the effect of long-term storage as well as heat processing on antibacterial activity of honey in order to improve this new potential quality standard.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2304-8158/9/9/1263/s1, Figure S1: Protein profile of commercial honey samples (*n* = 19) from supermarkets and three samples from local beekeepers, Figure S2: Protein profile of commercial honey samples (*n* = 17) from local food shops.

**Author Contributions:** Conceptualization, J.M.; Methodology, M.B., V.B., J.G.; Formal Analysis, J.G., V.B., M.B.; Investigation, J.M., M.B.; Resources, J.M.; Writing—Original Draft Preparation, J.M.; Writing—Review & Editing, J.M., M.B., V.B., J.G.; Visualization, J.M., Funding Acquisition, J.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences VEGA 2/0004/18.

**Conflicts of Interest:** The authors declare no conflict of interest.
