The topological features of the charge densities, ρ(r), and the chemical reactivity of two most biologically relevant and chemically interesting scaffold systems i.e. trans-communic acid and imbricatolic acid have been determined using density functional theory. To identify, characterize, and quantify efficiently, the non-covalent interactions of the atoms in the molecules have been investigated quantitatively using Bader's quantum theory of atoms-in-molecules (QTAIM) technique. The bond path is shown to persist for a range of weak H···H as well as C···H internuclear distances (in the range of 2.0–3.0 Å). These interactions exhibit all the hallmarks of a closed-shell weak interaction. To get insights into both systems, chemical reactivity descriptors, such as HOMO–LUMO, ionization potential, and chemical hardness, have been calculated and used to probe the relative stability and chemical reactivity. Some other useful information is also obtained with the help of several other electronic parameters, which are closely related to the chemical reactivity and reaction paths of the products investigated. Trans-communic acid seems to be chemically more sensitive when compared with imbricatolic acid due to its experimentally observed higher half-maximal inhibitory concentration (bioactivity parameter) value, which is in accordance with its higher chemical reactivity as theoretically predicted using density functional theory-based reactivity index. The quantum chemical calculations have also been performed in solution using different solvents, and the relative order of their structural and electronic properties as well as QTAIM-based parameters show patterns similar to those observed in gas phase only. This study further exemplifies the use and successful application of the bond path concept and the quantum theory of atoms-in-molecules.

Two biologically important molecules specioside (SS) and verminoside (VS) have been isolated from the ethanolic extract of stem bark of Kigelia pinnata. We have explored the electronic and spectroscopic properties of these two molecules on the basis of the Density Function Theory (DFT) quantum chemical calculations along with the correlations of biological efficacies and the results are presented in this paper. The structures of the molecules were established with the help of spectroscopic techniques (1H, 13C NMR, UV-VIS, FTIR) and chemical reactivity was compared by computed DFT theory using Becke3-Lee-Yang-Parr (B3LYP)/6-31G (d,p) data basis set. UV-Visible spectrum was obtained using Time Dependent DFT method. Electric dipole moment, polarizability, first static hyper polarizability and hyper conjugative interactions were also studied with the aid of natural bond orbital (NBO) analysis of these two compounds. The thermodynamic parameters of these compounds were determined at various temperatures. The HOMO, LUMO, chemical hardness (η), chemical potential (μ), electronegativity (χ), electrophilicity power (ω), the gap energy and NBO analysis of both the compounds have been discussed in this paper. Local reactivity was evaluated through the Fukui function i.

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Lupeol has been isolated from ethanol extract of stem bark of Bombax ceiba through normal phase column chromatography. Total fourteen derivatives of lupeol were synthesized and assayed for in vitro antitumor activities against MDA MB-231, HeLa and A549 cell lines. In cell proliferation experiments, pyrimidine-2(5H)-thione derivative (15) was found to be most potent and significantly inhibited all three tested cancer cell lines i. e. MDA MB-231 (IC 50 27.13 � 2.13), HeLa (IC 50 45.95 � 1.42) and A549 (IC 50 46.27 � 0.9). The (2, 4-dinitrophenyl) hydrazyl-3-lupeol Derivative (12) exhibited antitumor activity against MDA MB-231 (IC 50 35.88 � 1.9) and HeLa cells (IC 50 31.91 � 1.6) whereas (2, 4-dinitrophenyl)-2H-imidazole derivative (14) showed activity against MDA MB-231 (IC 50 38.05 � 1.9) and A549 (IC 50 42.01 � 0.90) cells respectively. Structure activity relationship is also described. Our study showed that compound 15 exhibited promising activity against MDA MB-231 and A549 cancer cell lines.