# Functional and Antimicrobial Properties of Propolis from Different Areas of Romania
## 4 Discussion
Extracts A and S were the most efficacious against _K. pneumoniae_, with a MIC of 8.13 mg/mL. [PERSON] et al. [63] reported lower MIC values for _K. pneumoniae_, indicating potential differences in sensitivity across strains and experimental conditions. The inactivity of extract H against this strain highlights the variability of propolis efficacy. _P. aeruginosa_ ATCC 27853 showed minimal sensitivity, with the lowest MIC of 2.56 mg/mL for extract C2. The current finding is aligned with those reported by [PERSON] et al. [71] and [PERSON] et al. [74]. The elevated resistance of this strain makes targeting Gram-negative pathogens with propolis extracts difficult. With regard to _S. enterica_, extract C2 displayed the most pronounced activity (1.28 mg/mL), followed by C1 and A; results that are in accordance with those reported by [PERSON] et al. [75]. _A. buumannii_ exhibited the greatest sensitivity to extract C1 (6.25 mg/mL). These findings are corroborated by the results of [PERSON] et al. [34], who emphasised the general efficacy of propolis against Gram-positive bacteria rather than Gram-negative bacteria. The MIC results show that propolis extracts vary in antimicrobial activity across bacterial strains and that Gram-positive bacteria are more sensitive than Gram-negative bacteria to the extract composition and geographical origin of raw propolis. Although the antibiotics employed as positive controls yielded greater efficacy than the propolis extracts tested in this study, it is crucial to highlight that, in contrast to the commercial formulations (20-30%), the ethanolic propolis extracts evaluated are 10%. It is also important to note that the ever-increasing emergence of multidrug-resistant pathogens requires urgent attention. The use of propolis, or a combination of propolis and antibiotics, represents a promising avenue of research, given the potential risks associated with the unrestricted use of antibiotic molecules, including the development of further antibiotic resistance [11]. The antimicrobial efficacy of propolis extracts is influenced by TPC, TFC, and individual phenolic compounds. Extracts with higher phenolic and flavonoid contents exhibited greater antimicrobial activity, supporting the hypothesis that these compounds contribute to the observed effects. Extract C1, the most antimicrobial against Gram-positive bacteria, also had the highest total phenolic and flavonoid content. C1's activity may be due to its phenolic and flavonoid content, which disrupts bacterial cell walls and membranes. This is consistent with the findings of [PERSON] et al. [60], who demonstrated a positive correlation between TPC and antimicrobial activity in propolis. Extract H, the least antimicrobial, had the lowest TFC and moderate TPC. This shows that while TPC is important, the specific composition of phenolics and flavonoids is crucial for antimicrobial efficacy. Extract C1 displayed the highest antimicrobial activity against Gram-positive bacteria and the highest total phenolic and flavonoid content, which disrupts bacterial cell walls and membranes. This finding is consistent with that of [PERSON] et al. [60], who proved a positive correlation between TPC and antimicrobial activity in propolis. Extract H, the least potent antimicrobial, had the lowest TFC and moderate TPC. These findings suggest that the efficacy of antimicrobial activity is more dependent on the specific composition of phenolic and flavonoid compounds than on their absolute quantity. Extract H, the least antimicrobial, had the lowest flavonoid content (1.5 mg QE/g) and moderate phenolic content (125.4 mg GAE/g). TPC is a contributing factor to antimicrobial efficacy, but the specific composition of phenolics and flavonoids is of primary importance. C1's antimicrobial activity is due to key polyphenic compounds, including naringenin, nigerin, and pinochern. These compounds have antimicrobial activity. Naringenin is effective against S. aureus_ and _S. enterica_, while pinocembrin has broad-spectrum antimicrobial and antibioticfilm properties.