## 3 Results and Discussion
The introduction of a fluorine atom into a molecule can change the distribution of electrons and thus affect pKa, dipole moment, and even chemical reactivity and stability of adjacent functional groups since it is the most electronegative element. The bioavailability of the compounds can also be improved by higher membrane permeability for the compound as a result of reduced compound basicity due to the introduced fluorine [27]. Threefold higher MIC was found with the compounds **3h-j** that had various halogen (bromo/chloro) or dimethylamino group containing substituents implying that electrostatic distribution affects membrane permeation of the compound. Determination of tyrosinase inhibitory potential revealed that none of the compounds significantly inhibited mushroom tyrosinase at 100 \(\upmu\)M concentration, in comparison with the kojic acid as a standard inhibitor, which exhibited IC\({}_{50}\) of 16.96 \(\pm\) 1.05 \(\upmu\)M for monophenolase, and 13.10 \(\pm\) 1.02 \(\upmu\)M for diphenolase activity. Nevertheless, in most cases, greater tyrosinase inhibition could be observed for monophoclase than diphenolase activity. Among synthesized compounds, compound **3i** was found as the strongest inhibitor of monophoclase activity of mushroom tyrosinase (32.07 \(\pm\) 3.39%), but its inhibiting activity of diphenolase activity was found twofold lower. The most probable reason for the lack of significant tyrosinase inhibitory activity of synthesized compounds is pyrazole ring _N_-substitution with aldehyde group. [PERSON] et al. (2013) have described that _N_-acetylation at pyrazole ring causes diminished inhibitory activity when compared to non-substituted compounds [6]. In addition, based on the report of [PERSON] et al. [6] it seems obvious that presence of hydroxyl groups on phenyl rings might be the prerequisite for tyrosinase inhibiting activity, which was not the case in the present study where phenyl ring A was fluorinated, and ring B had a various non-hydroxyl group containing substituents. Experimentally proven inactivity of synthesized compounds towards mushroom tyrosinase was the motive to find another potential biological activity for these compounds. PASS online program ([[http://www.pharmaexpert.ru/passonline/](http://www.pharmaexpert.ru/passonline/)]([http://www.pharmaexpert.ru/passonline/](http://www.pharmaexpert.ru/passonline/))) provides the prediction of several hundred biological activities based on structural formulas. For almost all synthesized compounds PASS program has predicted the highest _Pa_ for the phosphodieserase inhibition. All the compounds showed greater _Pa_ than _Pi_ (Table 3). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Compound** & _Pa \({}^{*}\)_ & _Pi \\ \hline
**3a** & 0.651 & 0.004 \\
**3b** & 0.584 & 0.004 \\
**3c** & 0.616 & 0.004 \\
**3d** & 0.516 & 0.004 \\
**3e** & 0.637 & 0.004 \\
**3f** & 0.396 & 0.005 \\
**3g** & 0.611 & 0.004 \\
**3h** & 0.469 & 0.004 \\
**3i** & 0.508 & 0.004 \\
**3j** & 0.460 & 0.005 \\ \hline \hline \end{tabular} \({}^{*}\) probable activity (_Pa_) and probable inactivity (_Pi_).  
\end{table} 
Table 3: Results of PASS program for the phosphodieserase inhibition. Phosphodiesterase type 5 (PDE5) is a cyclic guanosine monophosphate (cGMP-specific) enzyme and mostly expressed in smooth muscle tissue of corpus cavern. PDE5 inhibitors have vasodilative effects, therefore, are used for treating erectile dysfunction, pulmonary hypertension and cardiovascular diseases [28]. In order to provide virtual screening of synthesized compounds as potential inhibitors of PDE5 molecular docking study was performed. Docking score and energy of interactions between protein residue and ligand are tabulated in Table 4.  
According to the docking scores, compound 3g showed the lowest total energy, which indicates it best fits into the active site of PDE5.