Spectroscopic, structural and drug docking studies of carbocysteine

Carbocysteine or carbocisteine having the empirical formula C5H9NO4S,is one of the most therapeutically prescribed expectorant, sold under the brand name viz., Mucodyne (UK and India), Rhinathiol and Mucolite. In pediatric respiratory pathology, it can relieve the symptoms of obstructive pulmonary disease (COPD) and bronchiectasis. On the consideration of its extensive pharmaceutical usage and medicinal value, we have investigated its chemical structure and composition by employing various spectral techniques like H-1, C-13 NMR, FT-IR,Raman, UV-Visible spectroscopy and powder X-ray diffraction method. Density Functional Theoretical (DFT) studies on its electronic structure is also carried out. Drug docking studies were carried out to ascertain the nature of molecular interaction with the biological protein system. Furthermore theoretical Raman spectrum of this molecule has been computed and compared with the experimental Raman spectrum. The forbidden energy gap between its frontier molecular orbitals, viz., HOMO-LUMO is calculated and correlated with its observed lambda(max) value. Atomic orbitals which are mainly contributes to the frontier molecular orbitals were identified. Molecular electrostatic potential diagram has been mapped to explain its chemical activity. Based on the results, a suitable mechanism of its protein binding mode and drug action has been discussed. (C) 2017 Elsevier B.V. All rights reserved.