Molecular Docking, IR, Raman Studies on Heterocyclic Aromatic Compound

Review Article

Austin Chem Eng. 2015;2(1): 1016.

Molecular Docking, IR, Raman Studies on Heterocyclic Aromatic Compound

Uma Maheswari J¹* and Tom Sundius²

¹Department of Physics, Theivanai Ammal College for Women,Villupuram,India

²Department of Physics, University of Helsinki, Finland

*Corresponding author: Uma Maheswari J, Department of Physics, Theivanai Ammal College for Women,Villupuram, Tamil Nadu, India

Received: March 04, 2015; Accepted: June 03, 2015; Published: June 06, 2015


Quantum chemical calculations of energies, geometrical structure and vibrational wave numbers of clioquinol were carried out by DFT (B3LYP) method with 6-21G (d) basis set. The Fourier-Transform Infrared and Fourier- Transform Raman spectra of clioquinol were recorded in the region 4000-400 cm-1 and 3500-100cm-1. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated Potential Energy Distribution (PED). Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibration mode. A molecular docking study was performed and the results indicate for the future drug designing. Ramachandran plot supports the docking studies by providing the ψ and Ф values for an amino acid in a protein.

Keywords: FT-IR; FT-Raman; Molecular docking; Topology; PED; Ramachandran plot


Iodochlorhydroxyquin (clioquinol) is an antifungal drug and antiprotozoal drug. It is neurotoxic in large doses. It is a member of a family of drugs called hydroxyquinolines which inhibit certain enzymes related to DNA replication. The drugs have been found to have activity against both viral and protozoal infections [1]. A result at UCSF indicates that clioquinol appears to block the genetic action of Huntington’s disease in mice and in cell culture [2]. Evidence from phase 2 clinical trials suggested that clioquinol could halt cognitive decline in Alzheimer’s disease, possibly owing to its ability to act as a chelator for zinc and copper ions. This led to development of analogs including PBT2 as potential therapeutic compounds for the treatment of Alzheimer’s disease [3]. Literature says [3] that clioquinol acts directly on a protein called clock-1 and might slow down the aging process. Recent studies provides strong evidence that clioquinol is able to target tumor proteasome in vivo in a copperdependent manner, resulting in formation of an active AR inhibitor and apoptosis inducer that is responsible for its observed antiprostate tumor effect [4]. Di chen et al. reported that clioquinol was capable of binding copper and forming a complex as verified by XANES and EXAFS. Biochemical analysis revealed that clioquinol induced cancer cell death through apoptotic pathways that require caspase activity. It has anticancer effects both in vitro and in vivo [5].

Knowledge of drug-biomolecules interactions contributes to a better understanding of the transportation, metabolism, and toxicity of drugs at molecular level. Spectroscopic methods are powerful tools in coping with problem of molecular mechanisms with advantages of simplicity, rapidity and high sensitivity [6-8]. Quantum chemical computational methods have proved to be an essential tool for interpreting and predicting the vibrational spectra [9,10]. Now a days, sophisticated electron correlation and density functional theory calculations are increasingly available and deliver force field of high accuracy even for large polyatomic molecules [11,12]. Density Functional Theory calculations of vibrational spectra of many organic systems [13-16] have shown promising conformity with experimental results and they provide excellent vibrational frequencies of organic compounds if the calculated frequencies are scaled to compensate for the approximate treatment of electron correlation, for the basis set deficiencies and for the anharmonicity [17-19]. Molecular docking was further employed to find the ligand sites of clioquinol to understand the interaction. Knowledge about the site at which a ligand binds provides an important clue for predicting the function of a protein and is also often a prerequisible for performing docking computations in virtual drug design and screening. The aim of the present study is to give a complete description of the molecule geometry and molecular vibrations of the title molecule. For that purpose, quantum chemical computations were carried out for clioquinol using DFT method. These calculations are valuable for providing insight into the vibrational spectrum and molecular parameters is expected to be helpful in evaluating the potential of clioquinol to environment and human health.


The compound clioquinol in the solid form was obtained from the Sigma-Aldrich chemical company with a stated purity of 98% and used as such without further purification. The FTIR and FTRaman spectra of the sample were recorded in the region 4000-400 cm-1 and 3500-100 cm-1 respectively using BRUCKER IFS 66V FTIR spectrometer with a resolution of 0.5 cm-1 at RSIC, Chennai, India. All the sharp bands of the spectrum have an accuracy of ± 1cm-1. The experimental and simulated FTIR and FT-Raman spectra are shown in Figure 1 and 2.