Molecular Modeling for Generation of Structural and Molecular Electronic Descriptors for QSAR Using Quantum Mechanical Semiempirical and ab initio Methods

The major thrust of scientific research is to understand and explain the biological functions of biological systems in molecular terms. The development of techniques of molecular modeling has opened the prospects for understanding the function, reactivity and properties of biological systems in terms of molecular structure. QSARs quantify the connection between the structure and properties of molecules and allow the prediction of properties from structural and electronic parameters. The QSAR studies employ electronic, hydrophobic, structural and topological parameters of the compounds. In particular, electronic parameters are considered important in the establishment of QSAR models and are helpful to quantify different types of intermolecular and intramolecular interactions, as these interactions are usually responsible for properties of biological systems. The hydroxy substituted quinones and their derivatives are of considerable practical importance in the field of biology and pharmacology, as prominent family of pharmaceutically active and biologically relevant chromophores. Hydroxy naphthoquinone derivatives, in particular, have shown inhibitory effect on DNA topoisomerase-I and antiproliferative activity and cytotoxic activity [1, 5, 6]. We have generated the molecular electronic descriptors like the energies of HOMO and LUMO, dipole moment μ ionization potentials, heat of formation, total energy ET , electronic energy Eel, electronic transition energies and IHB strengths for the hydroxy derivatives of series of quinones by optimizing their geometries using the semiempirical and ab initio molecular modeling methods.