## 3 Results
### Enzyme Inhibitory Activity of Oak Bark Extracts  
The oak bark extracts were evaluated for their alfa-glycosidase, tyrosinase and acetyl-cholinesterasees inhibitory potential, and the results are presented in Table 5. \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **QREM** & **QRAM** & **QREUS** & **QRAUS** \\ \hline _C. albicans_ & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 \\ _C. parapsilosis_ & 5 & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 \\ _C. krusei_ & 2.5 & 2.5 & 5 & 5 \\ \hline \hline \end{tabular}  
MIC: minimum inhibitory concentration; QREM\(-\)hydroalcoholic extract obtained using MAE; QREM\(-\)aqueous extract obtained using MAE; QREUS\(-\)hydroalcoholic extract obtained using MAE; QRAUS\(-\)aqueous extract obtained using MAE.  
\end{table} 
Table 4: Antifungal activity (MIC in mg/mL) of the oak bark extracts. \begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**QREM**} & \multicolumn{2}{c}{**QRAM**} & \multicolumn{2}{c}{**QREUS**} & \multicolumn{2}{c}{**QRAUS**} \\ \cline{3-10}  & & **MIC** & **MBC** & **MIC** & **MBC** & **MIC** & **MBC** & **MIC** & **MBC** \\ \hline _S. aureus_ & Gram-positive & 0.3 & 0.3 & 0.3 & 5 & 0.3 & 0.6 & 0.6 & 0.6 \\ MRSA & bacteria & 1.25 & 1.25 & 0.6 & 1.25 & 1.25 & 1.25 & 0.6 & 0.6 \\ \hline _E. coli_ & Gram-negative & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 & \textgreater{}5 \\ _K. pneumoniae_ & bacteria & 1.25 & 5 & 0.6 & 0.6 & 1.25 & 2.5 & 0.6 & 0.6 \\ _P. aeruginosa_ & bacteria & 2.5 & 2.5 & 5 & 5 & 0.6 & 2.5 & 1.25 & \textgreater{}5 \\ \hline \hline \end{tabular}  
MIC: minimum inhibitory concentration; MBC: minimum bactericidal concentration; MRSA: methicillin-resistant _Staphylococcus aureus_; QREM\(-\)hydroalcoholic extract obtained using MAE; QRAM\(-\)aqueous extract obtained using MAE; QREUS\(-\)hydroalcoholic extract obtained using MAE; QRAUS\(-\)aqueous extract obtained using MAE.  
\end{table} 
Table 3: The antimicrobial activity (mg/mL) of the _Q. robur_ bark extracts. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Enzyme** & **Control** & **Tested Solutions** & **Values** \\ \hline \hline  & & QREM & 143.4 \\ \cline{3-5} Acetyl–cholinesterasees & & QRAM & 152.8 \\ (IC\({}_{\text{50}}\), \(\mu\)g/mL) & & QREUS & 148.4 \\ \cline{2-5}  & & QRAUS & 159.2 \\ \cline{2-5}  & Galantamine & & 0.0002 \\ \hline  & & QREM & 3.88 \\ \cline{3-5} Alfa-glucosidase & & QRAM & 4.07 \\ (IC\({}_{\text{50}}\), \(\mu\)g/mL) & & QREUS & 5.60 \\ \cline{3-5}  & & QRAUS & 4.945 \\ \cline{2-5}  & Acarbose & & 122.27 \\ \hline  & & QREM & 145.74 \\ \cline{2-5} Tyrosine & & QRAM & 172.22 \\ (IC\({}_{\text{50}}\), \(\mu\)g/mL) & & QREUS & 79.8 \\ \cline{2-5}  & & QRAUS & 234 \\ \hline Kojic acid & & 4.44 \\ \hline \hline \end{tabular}  
QREM\(-\)hydroalcoholic extract obtained using MAE; QRAM\(-\)aqueous extract obtained using MAE; QREUS\(-\) hydroalcoholic extract obtained using MAE; QRAUS\(-\)aqueous extract obtained using MAE; QRAUS\(-\)aqueous extract obtained using MAE; QRAUS\(-\)aqueous extract obtained using MAE.  
\end{table} 
Table 5: The in vitro enzyme inhibitory activity of the oak bark extracts. In all of the assayed activities, the anti-\(\alpha\)-glucosidase potential was the strongest, which can be observed from the IC\({}_{50}\) values and from the inhibition graph presented in Figure 3. In comparison to the positive control (acarbose), all the samples showed an inhibitory activity at least 10 times lower, and the best IC\({}_{50}\) was identified in the ethanolic extract that was obtained using MAE (QREM). In this case, the IC\({}_{50}\) values ranged from 3.88 to 5.60 ug/mL, significantly lower in comparison to the IC\({}_{50}\) of acarbose (122.27 ug/mL). However, the activity against tyrosinase and acetyl-cholinesterase was modest. All the extracts showed a moderate activity against tyrosinase and the highest activity was observed for the ethanolic extract that was obtained using UAE (QREUS).