## 3 Results  
### Evaluation of Extract Activity  
The extracts exhibited antimicrobial activity with varying effectiveness depending on the tested strain (Table 2). For the purpose of this study, inhibition zones were classified as follows: strong activity (\(\geq\)7 mm), moderate (2-6 mm), minimal (1 mm), and no activity (0 mm). Based on this classification, _C. sinensis_ and _R. ideaus_ demonstrated the largest activity, with maximum inhibition zones reaching 8.0 mm for _P. aeruginosa_ and _E. faecalis_ and 8.0 mm for _P. aeruginosa_, respectively. Extracts from _Q. robur_, _B. pendula_, _T. cordata_, and _S. alba_ displayed moderate antimicrobial activity, with inhibition zones ranging from 2.0 mm to 6.0 mm. No antimicrobial activity was observed for the extracts from _Coffea_ L., _R. canina_, _T. officinale_, _Q. suber_, _V. officials_, and _P. sylvestris_, with inhibition zones of 0.0 mm for all tested strains. The _U. dioica_ extract exhibited only minimal activity against _P. aeruginosa_, with an inhibition zone of 1.0 mm. The susceptibility analysis indicated that _P. aeruginosa_ and _E. faecalis_ were more susceptible to the tested extracts, whereas _P. vulgaris_ and _K. oxytoca_ exhibited higher resistance. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & & & & **Tested Bacteria** & & \\ \cline{2-7}  & & _P. aeruginosa_ & _P. vulgaris_ & _K. pneumoniae_ & _K. oxytoca_ & _E. faecalis_ & _S. marcescens_ \\ \cline{2-7}
**Plant Extract** & **Material** & \multicolumn{3}{c}{**Mean of Inhibition Zone [mm] (After Exclusion of the Well Diameter)**} & & & & \\ \hline _Coffea_ L. & grounds & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ _Camilla sinensis_ & grounds & **8.0** & **7.0** & **4.0** & **2.0** & **8.0** & **4.0** \\ _Urtic dioica_ L. & leaves & **1.0** & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ _Tilia cordata_ Mill. & flowers & **6.0** & **4.0** & **3.0** & **2.0** & 0.0 & **3.0** \\ _Quercus robur_ L. & flowers & **6.0** & **2.0** & **4.0** & **5.0** & **6.0** & **4.0** \\ _Rosa canina_ L. & fruit & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ _Betula pendula_ Roth & bark & **4.0** & **4.0** & **5.0** & **6.0** & **4.0** & **4.0** \\ _Tarazucum officinal_ & root & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ [PERSON]. Wiggers coll. & expanded & & & & & & \\ _Quercus suber_ L. & bark & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ _Rubus ideaus_ L. & shoots & **8.0** & **4.0** & **6.0** & **6.0** & **5.0** & **4.0** \\ _Salix alba_ L. & bark & **4.0** & **4.0** & **4.0** & **4.0** & **4.0** & **2.0** \\ _Verbena officinalis_ & shoots & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ _Pinus sylvestris_ L. & shoots & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 & 0.0 \\ \hline \multicolumn{7}{c}{* Positive control:} & 37.5 & 36.5 & 38.0 & 30.0 & 22.5 & 41.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Inhibition zone diameter (mm) of tested plant extracts in the well diffusion method. For further studies on the assessment of combined effects, extracts from the following raw materials were selected: _C. sinensis_, _T. cordata_, _Q. robur_, _B. pendula_, _R. ideaus_, and _S. alba_. Combinations of plant extracts were prepared in a 1:1 ratio and tested at the same total volume (100 \(\upmu\)L) as single extracts. The percentage increase in antimicrobial activity of the combined extracts was calculated relative to the most active single extract in each pair. This approach assumes that any observed enhancement beyond the highest individual activity may indicate a potential synergistic or additive effect between the extracts. This method provides a conservative estimate of enhanced antimicrobial activity, as it compares the mixture directly with the stronger of the two components. To achieve this, an experimental setup was prepared in which the extracts were combined according to the proposed matrix (Table 3). The recovery yield of dried extracts obtained after spray drying varied among the plant species, with _Camellia sinensis_ exhibiting the highest recovery (10.59%), followed by _Rubus ideaus_ (7.86%) and _Tilia cordata_ (5.34%) (Table 4).