A quantitative structure-activity relationship (QSAR) study is a helpful approach to quantitatively understand the relationships between molecular structures of inhibitors and their biological activities [39] [40] [41] [42] [43] [44] [45] [46] . Pharmacophore modeling and 3D-QSAR studies have been successfully applied previously for various drug discovery research, including glycoprotein (GP) IIb/IIIa antagonists, H 3 -antihistaminics, and dihydrofolate reductase inhibitors [47] [48] [49] [50] [51] . Electronic molecular features such as electron density, frontier molecular orbital density fields such as lowest unoccupied molecular orbital (LUMO), highest occupied molecular orbital (HOMO) and molecular electrostatic map have also been revealed to be significant in other QSAR studies to explain biological activity and molecular properties [52] . The HOMO density field was useful in a study of ACE inhibitors, and the LUMO density field was found to be important for explaining the TA100 mutagenicity [53, 54] . Thus, determining molecular electronic properties responsible for the potent activity of selected chymase inhibitors should illuminate the fundamental molecular level forces responsible for their potency.