## 3 Results and Discussion
### Acetylcholinesterase Inhibitory Assay  
The acetylcholinesterasecholinesteraseerase inhibitory activity of the synthesized compounds was evaluated employing Adewusi adaptation of Ellmans spectrophotometrical assay [30], using galantamine as a reference. The results for these experiments are shown with their IC\({}_{50}\) values on Table 2. The compounds that were chosen for screening can be divided into two groups based on their structural features: chalcones and flavones. Chalcones are 1,3-diphenyl-2-propene-1-one systems, in which two aromatic rings are linked by a three carbon \(\alpha\), \(\beta\)-unsaturated carbonyl system. The compounds with this backbone have been reported to possess various biological activities [53]. The IC\({}_{50}\) values of these compounds are listed in Table 2. [PERSON] et al. [54] reported that hydroxyl groups in ortho position of the A ring of chalcones, are an important structural element in the AChE inhibitory activity; however, in our study all the synthesized chalcones had the \(o\)-OH substitution in their A ring, and most of them displayed no inhibition effect in the tested concentration scale. Compounds **2c**, **2i**, and **2k** showed an inhibitory effect with IC\({}_{50}\) values of 52.7, 80.4, and 66.4 \(\mathrm{\SIUnitSymbolMicro mL}\), respectively, in contrast to the rest of molecules that presented results above 150 \(\mathrm{\SIUnitSymbolMicro mL}\). On the other hand, results of the flavone group **3a-3k** that are based upon a fifteen-carbon skeleton consisting of two benzene rings (A and B) linked via a heterocyclic pyrane ring (C) (Figure 1) indicate that they were more active than the chalcone group. Only the compounds **3a**, **3h**, **3i**, and **3k** presented poor inhibition as compared to the rest of flavones that, in the majority, have hydroxyl or methoxyl groups in their B ring, where compounds **3e**, **3g**, **3f**, and **3b** outstand with an IC\({}_{50}\) of 43.5, 43.5, 60.0, and 61.2 \(\mathrm{\SIUnitSymbolMicro mL}\), respectively; however, compound **3d** with \(o\)-OH, \(m\)-NO\({}_{2}\) in the B ring was found to be the best flavone inhibitor of AChE, having an IC\({}_{50}\) of 26.8 \(\mathrm{\SIUnitSymbolMicro mL}\). It has been acknowledged that hydroxyl and methoxyl groups in the A and B rings of flavones are deeply related to bioactivity and their capacity to protein bonding, being the hydroxyl groups that are favorable for the flavonoids interaction with acetylcholinesteraseinesterase by hydrogen bonds formation in the enzyme peripheral anionic site (PAS) [55], which would explain the activity showed by compounds **3b**,  
\begin{table} \begin{tabular}{c c c c} \hline \hline
**Compound** & **IC\({}_{\text{50}}\) (\(\mathrm{\SIUnitSymbolMicro mL}\))** & **Compound** & **IC\({}_{\text{50}}\) (\(\mathrm{\SIUnitSymbolMicro mL}\))** \\ \hline
**2a** & \textgreater{} 150 & **3a** & \textgreater{} 150 \\
**2b** & \textgreater{} 150 & **3b** & 61.2 \(\pm\) 1.39 \\
**2c** & \textgreater{} \(52.7\pm 11.98\) & **3c** & 78.4 \(\pm\) 1.92 \\
**2d** & \textgreater{} \(21.5\pm 2.61\) & **3d** & 26.8 \(\pm\) 5.91 \\
**2e** & \textgreater{} \(150\) & **3e** & 43.5 \(\pm\) 4.31 \\
**2f** & \textgreater{} \(150\) & **3f** & 60 \(\pm\) 9.96 \\
**2g** & \textgreater{} \(150\) & **3g** & 43.5 \(\pm\) 2.52 \\
**2h** & \textgreater{} \(150\) & **3h** & \textgreater{} 150 \\
**2i** & \textgreater{} \(80.4\pm 5.97\) & **3i** & \textgreater{} 150 \\
**2j** & \textgreater{} \(150\) & **3j** & 77.6 \(\pm\) 31.89 \\
**2k** & \textgreater{} \(66.4\pm 6.15\) & **3k** & \textgreater{} 150 \\ \hline \multicolumn{3}{c}{*Gantantamine} & \multicolumn{3}{c}{0.574 \(\pm\) 0.07} \\ \hline \hline \end{tabular}   
* *3c, and 3d (61.2, 78.4, and 26.8 ug/mL). On other hand, the presence of methoxyl groups in flavonoids favors the inhibition effect due to the interaction with residue Trp279, located in the entrance to the active site (in the PAS), this could explain the results obtained for analogs 3e-3g.