## 3 Results and Discussion
### Antimicrobial Activity  
The in vitro diffusion-based method was used to determine the antimicrobial activity of the BC extract against three bacterial strains with pathogenic potential: _E. coli_, _S. aureus_ and _L. monocytogenes_. The BC extract exerted good antimicrobial action against the Gram-negative strain, _E. coli_, compared to _S. aureus_ (Table 5, Figure S1). However, no effect of the bioactive compounds extracted from BC against _L. monocytogenes_ was observed. The antibacterial activity of the extract may be attributed to the cumulative effects of all bioactive compounds, as well as the synergic interactions among them. Chlorogenic acid, the main phenolic acid in BC pomace, has the potential to increase the permeability of both the outer and plasma membranes, disrupts their integrity, depletes the intracellular potential and facilitates the release of cytoplasmic macromolecules, ultimately leading to cell death [41]. However, chlorogenic acid does not exhibit direct membrane disruption but induces a significant decrease in intracellular adenosine triphosphate (ATP) levels, likely affecting the material and energy metabolism and interfering with cell signaling transduction [42]. Catechins, as other major compounds in BC pomace, exhibit multiple antibacterial mechanisms, primarily linked to bacterial cell wall and membrane disruption, but they also induce oxidative stress and cause DNA damage by inhibiting DNA repair mechanisms and generating reactive oxygen species (ROS), particularly hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)). Catechins can interact with bacterial membranes, leading to protein deposition and the inhibition of peptidoglycan biosynthesis, which leads to membrane perforation and reduced fluidity [43]. Catechins have demonstrated bactericidal effects on both Gram-positive (_Streptococcus mutans_ and _Streptococcus pneumoniae_) and Gram-negative bacteria (_Pseudomonas aeruginosa_ and _E. coli_), including multidrug-resistant strains [44]. Quercetin, a well-represented flavonoid in BC pomace, exhibits broad-spectrum antimicrobial activity against drug-resistant Gram-positive and Gram-negative bacteria (_E. faecalis_, _P. mirabilis_, _P. aeruginosa_, _S. aureus_, _Salmonella enterica_, _E. coli_) [45]. Its antimicrobial effects \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Bacterial Strain**} \\ \cline{2-4}  & _E. coli_ & _S. aureus_ & _L. monocytogenes_ \\ \hline Inhibition zone diameter, mm & 25.50 \(\pm\) 0.70 & 17.00 \(\pm\) 1.41 & nd \\ MIC, mg/mL & 0.5 & 1.0 & - \\ MBC, mg/mL & \textgreater{}1.0 & \textgreater{}1.0 & - \\ \hline nd—not detected. & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The inhibition zone diameters, the minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of BC extract against _Escherichia coli_, _Staphylococcus aureus_ and _Listeria monocytogenes_. are mediated through multiple mechanisms, including cell wall and membrane disruption, interfering with DNA replication and transcription processes, thereby inhibiting nucleic acid and protein synthesis and further bacterial growth and causing the suppression of virulence factors, enzyme inhibition and biofilm prevention [46; 47; 48]. [PERSON] and [PERSON] [49] highlighted the higher in vitro bacterio-static activity of the fruit juice of _Aronia melanocarpa_ against _S. aureus_ compared to _E. coli_. [PERSON] et al. [11] tested the antimicrobial activity of dried BC fruits, emphasizing the potential of hydroalcoholic extracts against _Bacillus cereus_ and _S. aureus_ strains, compared to aqueous extracts of frozen or dried samples. Furthermore, both aqueous and hydroalcoholic extracts of fresh fruits inhibited the growth of the Gram-negative bacterium, _Pseudomonas aeruginosa_, but did not influence the growth of the _E. coli_ strain [11]. The antimicrobial activity of the BC extract, as indicated by the MIC values, was determined to be at 0.5 mg/mL for _E. coli_ and 1 mg/mL for _S. aureus_, respectively (Table 5).