The hepatoprotective active phytochemical constituents from the ethanolic extracts of the fruits of Cucumis trigonus Roxb. and Cucumis sativus Linn. were identified by GC-MS analysis. The density functional theory (DFT) of these molecules was calculated by density functional B3LYP methods using B3LYP/6-311++G(d,p) basis set. The optimized geometries of phytochemical constituents were evaluated. Physicochemical properties such as HOMO, LUMO, ionization potential, electron affinity, electronegativity, electrochemical potential, hardness, softness, electrophilicity, total energy, and dipole moment have also been recorded. These are very important parameters to understand the chemical reactivity and biological activity of the phytochemical constituents. Glycodeoxycholic acid and 2-(2-methylcyclohexylidene)-hydrazinecarboxamide were found to be effective drugs selected on the basis of their HOMO and LUMO energy gap and softness. The effective properties of these compounds may be due to the presence of amino, carbonyl, and alcohol as a functional group. 1. Introduction DFT is the connection between the density and the wave function which was developed by Hohenberg and Kohn and stated in the Hohenberg-Kohn theorems [1, 2]. The first theorem shows that the Hamiltonian is fully determined by the ground state density, which means that all the physical properties of the system are completely determined by the ground state density. The second theorem demonstrates that the energy functional can be used to find the ground state density. Importantly, the excited states need to be determined in a different way. During the last decade, computer simulations based on a quantum-mechanical description of the interaction between electrons and atomic nuclei have strongly influenced the development of material science [3]. The major advantage from a computational point of view is that the electronic density depends only on the three variables of space, while the wave function for an N electron system depends on 3N variables. DFT uses the B3LYP/6-311++G(d,p) hybrid functional in the gas phase. The presence of phytochemical constituents in the ethanolic extracts of the fruits of Cucumis trigonus and Cucumis sativus is responsible for curing liver disorder. Silymarin is used as a potential hepatoprotective agent. In the present work, a comparative DFT study of phytochemical constituents identified from the ethanolic extracts of the fruits of Cucumis trigonus and Cucumis sativus has been performed. Gaussian 09W program and Gauss-View molecular visualization program package on the
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