## 3 Results and Discussion
### Antibacterial Activity and QSAR Studies
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{_E. coli_} & \multicolumn{3}{c}{_S. enterica_} & \multicolumn{3}{c}{_S. aureus_} \\  & & \multicolumn{2}{c}{**ATCC 25922**} & \multicolumn{3}{c}{**SL 5676**} & \multicolumn{3}{c}{**ATCC 25923**} \\ \cline{2-10}
**Compound** & \multicolumn{2}{c}{**MIC(\(\mu\)M)**} & \multicolumn{2}{c}{**MIC**} & \multirow{2}{*}{**pMIC**} & \multirow{2}{*}{**MIC(\(\mu\)M)**} & \multirow{2}{*}{**MIC(\(\mu\)M)**} & \multirow{2}{*}{**pMIC**} & \multirow{2}{*}{**MIC(\(\mu\)M)**} & \multirow{2}{*}{**MIC(\(\mu\)M)**} & \multirow{2}{*}{**pMIC**} & \multirow{2}{*}{**MIC(\(\mu\)M)**} & \multirow{2}{*}{**pMIC**} \\  & **MIC(\(\mu\)M)** & & & & & & & & \\  & **MIC(\(\mu\)M)** & & & & & & & & \\ \hline TPZ **(1)** & 44.9 & 8.0 & \(-\)1.65 & 44.9 & 8.0 & \(-\)1.65 & 89.8 & 16.0 & \(-\)1.95 \\ **(2)** & 1.1 & 0.25 & \(-\)0.04 & 1.1 & 0.25 & \(-\)0.04 & 2.2 & 0.5 & \(-\)0.34 \\ **(3)** & 8.5 & 2.0 & \(-\)0.93 & 8.5 & 2.0 & \(-\)0.93 & 4.3 & 1.0 & \(-\)0.63 \\ **(4)** & 4.2 & 1.0 & \(-\)0.62 & 2.1 & 0.5 & \(-\)0.32 & 2.1 & 0.5 & \(-\)0.32 \\ **(5)** & 16.0 & 4.0 & \(-\)1.20 & 8.0 & 2.0 & \(-\)0.90 & 8.0 & 2.0 & \(-\)0.90 \\ **(6)** & 32.0 & 8.0 & \(-\)1.51 & 16.0 & 4.0 & \(-\)1.20 & 4.0 & 1.0 & \(-\)0.60 \\ **(7)** & 58.4 & 16.0 & \(-\)1.77 & 58.4 & 16.0 & \(-\)1.77 & 116.7 & 32.0 & \(-\)2.07 \\ **(8)** & 412.6 & 128.0 & \(-\)2.62 & 412.6 & 128.0 & \(-\)2.62 & 103.2 & 32.0 & \(-\)2.01 \\ **(9)** & 249.8 & 64.0 & \(-\)2.40 & 249.8 & 64.0 & \(-\)2.40 & 249.8 & 64.0 & \(-\)2.40 \\ **(10)** & 114.6 & 32.0 & \(-\)2.06 & 114.6 & 32.0 & \(-\)2.06 & 114.6 & 32.0 & \(-\)2.06 \\ \hline Chloramphenicol & 12.4 & 4.0 & & 12.4 & 4.0 & & 24.8 & 8.0 & \\ Ciprofloxacin & 0.18 & 0.06 & & 0.09 & 0.03 & & 0.04 & 0.02 & \\ Nitrofurantoin & 16.8 & 4.0 & & 33.6 & 8.0 & & 8.4 & 2.0 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The minimum inhibitory concentration (MIC) and inhibitory activity (in terms of pMIC = \(-\)log MIC (\(\mu\)M)) of TPZ **(1)**, its derived compounds **(2–10)** and the reference antibiotics used against Gram-negative (_E. coli_ and _S. enterica_) and Gram-positive (_S. aureus_) bacterial strains. correlations have been observed between electrochemical redox potentials and inhibitory activities of the entire series of the compounds, while certain dependences have been found for a small and structurally uniform set of molecules within a narrow range of their redox potentials. These data show that the electron-accepting potency of the compounds as the driving force for their reductive activation cannot alone justify the observed activity. Table 2 provides a set of additional indices of the test compounds, including lipophilicity (octanol/water partition coefficient, Log P\({}_{\text{oct}}\)), molecular weight (MW) and volume (MV), polar surface area (PSA), H-bond donors (HBD) and H-bond acceptors (HBAs). All compounds followed [PERSON]'s rule predictive to good bioavailability (MW \(<\) 500, Log P \(<\) 5, HBD \(<\) 5, and HBA \(<\) 10) [47]. For the whole set of tested TPZs, the reliable negative dependences between the inhibitory potencies of the compounds and their Log P\({}_{\text{oct}}\) values were observed for _E. coli_ (R = 0.84; F = 14.63) and _S. enterica_ (R = 0.86; F = 22.69), while to a markedly lesser extent for _S. aureus_ (R = 0.68; F = 7.11), suggesting that the more hydrophilic nature of the substituents leads to the higher inhibitory activities of TPZ derivatives. Furthermore, the inhibitory potencies of the compounds towards all the tested strains decreased with an increase in their molecular weight (R = 0.75-0.86), with the exception of TPZ (**1**), and showed a slight tendency to decrease with an increase in their polarity, expressed in terms of the polar surface area (PSA) (R = 0.70-0.74) and the H-bond acceptor counts (HBAs) (R = 0.55-0.60), by excluding the low potent derivative (**10**).