## 2 Results & Discussion
### Biological Studies
#### 2.2.3 Antiproliferative Activity
\begin{table}
\begin{tabular}{c c c c c} \hline
**Compound** & **R** & _A. niger_ & **C. _tropicalis_** & *** DU-145** & *** Human Normal Liver** \\
**No.** & & (MIC = uM \(\pm\) SD) & (MIC = uM \(\pm\) SD) & (IC\({}_{50}\) = ug/mL \(\pm\) SD) & **Cells (LO2; ug/mL)** \\ \hline
**22** & Phenyl & \textgreater{}200 \(\pm\) 0.91 & \textgreater{}200 \(\pm\) 0.58 & 40 \(\pm\) 1 & \textgreater{}40 \\
**23** & 4′′-chlorophenyl & 100.57 \(\pm\) 0.52 & 100.57 \(\pm\) 0.16 & 18 \(\pm\) 2 & \textgreater{}40 \\
**24** & 4′′-fluorophenyl & 106.06 \(\pm\) 0.19 & 106.06 \(\pm\) 0.88 & 47 \(\pm\) 2 & \textgreater{}40 \\
**25** & 4′′-nitrophenyl & 97.34 \(\pm\) 0.28 & 97.34 \(\pm\) 0.52 & 112 \(\pm\) 2 & \textgreater{}40 \\
**26** & 4′′-hydroxyphenyl & \textgreater{}200 & \textgreater{}200 \(\pm\) 0.66 & 121 \(\pm\) 2 & \textgreater{}40 \\
**27** & 4′′-methylphenyl & \textgreater{}200 & \textgreater{}200 \(\pm\) 0.73 & 132 \(\pm\) 2 & \textgreater{}40 \\
**28** & 4′′-methoxyphenyl & \textgreater{}200 & \textgreater{}200 \(\pm\) 0.22 & 88 \(\pm\) 2 & \textgreater{}40 \\
**29** & 4′′-methylaminophenyl & 195.84 \(\pm\) 0.98 & \textgreater{}200 \(\pm\) 0.81 & 24 \(\pm\) 2 & \textgreater{}40 \\
**30** & 2′′-difluorophenyl & **50.04** \(\pm\) 1 & **50.04** \(\pm\) 0.22 & 10 \(\pm\) 2 & \textgreater{}40 \\
**31** & 2′′,4′′-dichlorophenyl & **45.37** \(\pm\) 0.66 & **45.37** \(\pm\) 0.18 & 12 \(\pm\) 2 & \textgreater{}40 \\
**32** & 3′′,4′′-dimethoxyphenyl & **46.52** \(\pm\) 0.99 & 186.17 \(\pm\) 0.63 & 72 \(\pm\) 2 & \textgreater{}40 \\
**33** & 3′′-methyl′′-hydroxyphenyl & \textgreater{}200 \(\pm\) 0.87 & \textgreater{}200 \(\pm\) 0.29 & 110 \(\pm\) 1 & \textgreater{}40 \\
**34** & 3′′,4′′-7′′-trimethoxyphenyl & 85.60 \(\pm\) 0.55 & 85.60 \(\pm\) 0.90 & 56 \(\pm\) 2 & \textgreater{}40 \\
**35** & 2′′-pyridinyl & 112.39 \(\pm\) 0.77 & **56.19** \(\pm\) 0.34 & **5 \(\pm\) 1** & \textgreater{}40 \\
**36** & 3′′-pyridinyl & 112.39 \(\pm\) 0.23 & 112.39 \(\pm\) 0.30 & 78 \(\pm\) 2 & \textgreater{}40 \\
**37** & 4′′-pyridinyl & \textgreater{}200 \(\pm\) 0.58 & 112.39 \(\pm\) 0.61 & 52 \(\pm\) 2 & \textgreater{}40 \\
**38** & 2′′-thienyl & 104.14 \(\pm\) 0.71 & 110.44 \(\pm\) 0.38 & 82 \(\pm\) 2 & \textgreater{}40 \\
**39** & 2′′-furfuryl & 116.92 \(\pm\) 0.82 & \textgreater{}200 \(\pm\) 0.72 & 96 \(\pm\) 2 & \textgreater{}40 \\
**40** & 5′′-pyrrolyl & \textgreater{}200 \(\pm\) 0.85 & \textgreater{}200 \(\pm\) 0.53 & 105 \(\pm\) 1 & \textgreater{}40 \\ Fluconazole & - & 84.14 \(\pm\) 0.19 & 63.10 \(\pm\) 0.44 & - & - \\ Methotrexate & - & - & - & 11 \(\pm\) 1 & \textgreater{}75 \\ \hline \end{tabular} The numbers in bold designate the activity of the compounds with more potency. * Data are the mean \(\pm\) SD (\(n\) = 3); IC\({}_{50}\) in ug/mL. The target hybrids and the standard were dissolved in DMSO and diluted with culture medium containing DMSO (0.1%). The control cells were treated with culture medium containing DMSO (0.1%).  
\end{table} 
Table 2: Antifungal (uM), antiproliferative and cytotoxic (ug/mL) activities of chloropyrazine-tethered pyrimidine hybrids (**22**–**40**). Neither disubstitution nor trisubstitution of the phenyl ring with electron-donating groups brought any significant change in activity. Among the compounds bearing biososteric scaffolds, the activity ranged from 5 \(\pm\) 1 to 105 \(\pm\) 1 \(\upmu\)g/mL. The best activity was observed for compound **35**, with an IC\({}_{50}\) value of 5 \(\pm\) 1 \(\upmu\)g/mL, which was twofold more active than the standard drug, i.e., methotrexate (11 \(\pm\) 1 \(\upmu\)g/mL). The order of activity of this group of derivatives was 2''-pyridinyl > 4''-pyridinyl > 3''-pyridinyl > 2''-thienyl > 2''-furyl > 5''-pyrrolyl. The cytotoxicity against normal human liver cell lines (LO2) of compounds **22-40** and methotrexate was found to be greater than 40 \(\upmu\)g/mL and 75 \(\upmu\)g/mL respectively, indicating less selectivity of compounds towards the normal human liver cells over the prostate cancer cell lines, indicating the safety of the target compounds.