## 4 Antimicrobial Properties of Honey  
Phenolic compounds critically modulate the antimicrobial properties of honey against common wound infections-causing strains, both Gram-positive, such as _Staphylococcus aureus (S. aureus)_ and _Enterococcus faecalis (E. faecalis)_, and Gram-negative bacteria as _Escherichia coli (E. coli)_ and _Pseudomonas aeruginosa (P. aeruginosa)_. When tested using a disc diffusion method, phenolic acid extracts were found to inhibit bacteria at a lower minimal inhibitory concentration (MIC) than the correspondent whole honey sample extract. This shows the prominent contribution of phenolic constituents, working synergistically, to the overall honey antibacterial activity [51]. Such phenolics-mediated anti-bacterial action seems to rest on a sophisticated balance between radical scavenging and pro-oxidants functions: depending on the concurring factors (i.e., hydrogen peroxide-rich honeys and the presence of transition metals), these renowned antioxidant agents can in fact auto-generate reactive oxygen species (ROS) and activate hydroxyl radicals. This triggers propagation of the Fenton reaction [74; 75], resulting in the observed antibacterial effect by bacterial damage. The direction that this equilibrium tends to also depends on the pH value: pro-oxidant action has been observed at fairly neutral pH, such as in diluted honeys [76]. The total phenolic content of honeys from Nordic countries has been shown to correlate with their inhibitory capacity against _S. aureus_ at 15% dilution (r = 0.57), with buckwheat, heather, sweet clover, and polyfloral honeys having the most pronounced antibacterial activity [42]. However, the total phenolic content and antioxidant activity of Scottish honeys of different botanical origins have not been found to be correlated with antibacterial activity [65]. The investigation of [PERSON] et al. on Brazilian honeys confirmed these findings, but a significant correlation (r = 0.4424) was instead observed between total flavonoids levels and antibacterial activity against _Bacillus cereus (B. cereus)_[77]. Nonetheless, the determinant factor for honey antimicrobial activity is yet to be unequivocally agreed on, which complicates the comparison between honey varieties described in healing applications. A conventional simplification leads to a distinction between peroxide and non-peroxide antibacterial activity: the first being hydrogen peroxide-mediated and the latter often identified with Manuka honey but not limited to it. However, the hypothesis of a multifactorial system seems more verisimilar, and it is generally accepted [78]. The osmotic pressure generated upon honey application on a wound site is regarded to be a primary contributor to the pro-healing features of honey of all botanical origins. In fact, the flux of fluids along the concentration gradient due to honey's high sugar content effectively washes the wound area from contaminants, debris, and bacteria, and it transports nutrients while regulating the moisture balance on the exudative wound [79]. [PERSON] et al. reported that a negative sugar control (consisting of a saturated solution of 38.5% fructose, 33.3% glucose, 6.2% maltose, and 7.3% sucrose in distilled water) inhibited the bacteria tested although not as effectively as the compared honey samples [65]. A similar observation was made in a study by [PERSON] et al., with artificial honey prepared with analogous sugar composition to Finnish honey and acidified to pH 3.5 with HCI [42]. However, a 75% sucrose (\(w/w\)) artificial honey did not show antibacterial activity against any of the bacteria tested by [PERSON] et al. [80]. Therefore, it is suggested that the high osmolality is not decisive to the medicinal properties of honey by itself, although it could contribute to them. Honey presents an intrinsic acidic pH, typically ranging between 3 and 4.7, due to its organic acids content [48; 49; 81].