When the whole dataset of molecules was taken into account, an apparent trend of inhibitory activity (IC 50 ) data with an increase in HOMO energy was observed ( Figure 10 ). For all compounds, HOMO energy ranges between −5.619 and −6.415 eV. High value of E HOMO is likely to indicate a tendency of the molecule to donate electrons to appropriate acceptor molecule of low empty molecular orbital energy. The correlation of HOMO energies with IC 50 data indicates that the HOMO of the inhibitor may transfer its electrons to less energy, LUMO, of some amino residues in the active site of chymase. The calculations show that compounds 1 and 20 have shown the highest (−5.873 eV) and lowest (−6.415 eV) HOMO level energies respectively. This trend is in good agreement with the experimental observations suggesting that compounds 1 and 20 have exhibited the highest (0.46 nM) and lowest (5900 nM) inhibitory profile, respectively, in all investigated chymase inhibitors. While BTB (BTB02076) has shown highest (−5.619 eV) HOMO level energy among hit compounds even higher than HOMO energy level of compound 1, the other two hit compounds also showed higher E HOMO than the least active compound of the data set. In a previous study, a high HOMO energy level also played an important part in activity of the most active dual and selective LOX inhibitors [61] . Moreover, a clear trend between the inhibitory activity (IC 50 ) data and LUMO energy of all compounds was also revealed. For all compounds, LUMO energy ranged between −0.631 and −2.275 eV. Compound 1 and BTB showed highest LUMO level energies; and least active compounds 19 and 20 demonstrated LUMO with lowest energies.