Synthesis and Evaluation of Antimicrobial Activity of the Rearranged Abietane Prattinin A and Its Synthetic Derivatives.

Synthesis of the natural product prattinin A and some new derivatives has been achieved using abietic acid. The final products and a selection of intermediates were evaluated for their antibacterial activity against three human pathogenic bacteria: E. coli, P. aeruginosa, and S. aureus. The results showed that the antibacterial activity varies depending on the chemical structure of the compounds. Notably, compound 27 exhibited the most potent activity against E. coli and P. aeruginosa, with a minimal inhibitory concentration (MIC) of 11.7 µg/mL, comparable to that of the standard antibiotic ciprofloxacin, and strong activity against S. aureus, with an MIC of 23.4 µg/mL. Furthermore, we assessed the stability of these derivative compounds as potential antimicrobial agents and determined their interactions with the crystal structure of the protein receptor mutant TEM-12 from E. coli (pdb:1ESU) using molecular docking via UCSF Chimera software 1.17.3. The results suggest that 27 has potential as a natural antibiotic agent.

In silico discovery of novel inhibitors from Northern African natural products database against main protease (Mpro) of SARS-CoV-2.

The recent outbreak of COVID-19 (Coronavirus Disease 2019), caused by a novel SARS-CoV-2 virus, has led to public health emergencies worldwide where time is as important as equipment to save lives. Antimalarial drugs such as hydroxychloroquine and chloroquine derivatives are used in emergencies but they are not suitable for patients with high blood pressure, diabetes and heart problems. Since there are no approved drugs for this disease, science is challenged to find vaccines and new drugs. Therefore, as part of our Silico drug design strategy, we identified drug-like compounds that inhibit replication of the main protease (Mpro) of SARS-CoV-2 based on receptor-based virtual database screening, molecular docking, molecular dynamics, and drug-similarity profiling from the NANPDB natural products database available at North African. The two resulting hit compounds named 5- Chloro-Omega-hydroxy-1-O-methylemodin and cystodion E showed the highest binding energy with Mpro of SARS-CoV-2 and strong inhibitory activity compared with the previously published N3 inhibitor. The complexes of these two compounds were validated by molecular dynamics analysis (RMSD, RMSF, Rg, total number of hydrogen bonds and secondary structure fractions of the protein in the complex) as the best method to evaluate the biological stability of the system. Therefore, these molecules deserve more attention in drug development compared to COVID-19. HighlightsA large database of natural compounds was screened against nCoV-2's Mpro.Molecular docking and Molecular dynamics were used as powerful methods.Two compounds were found are very attractive to inhibit Mpro of nCoV-2.ADME-Tox profiling is evaluated the active compounds are not cancerogenic.Communicated by Ramaswamy H. Sarma.

Newly synthesized (R)-carvone-derived 1,2,3-triazoles: structural, mechanistic, cytotoxic and molecular docking studies.

In the current study, natural (R)-carvone was used as starting material for the efficient synthesis of several 1,2,3-triazole derivatives. The produced products were obtained in good yields and characterized by 1H and 13C NMR and HRMS analysis. The newly synthesized monoterpenic 1,2,3-triazole 4 and derivatives were analyzed by viability tests (MTT) for their cytotoxic activity against three human cancer cells. Product 5 showed a medium antitumor activity, for which the IC50 values against selected cells HT-1080, A-549 and MCF-7 were 29.25 µM, 31.62 µM and 26.02 µM, respectively. The regioselectivity of the condensation reaction and the molecular structure of the title compounds were determined by Density Functional Theory (DFT) using B3LYP calculations at 6-311 + G(d,p) level. The orbitals HOMO and LUMO were studied to determine the electronic properties of the synthesized compounds. In addition, the global reactivity indices were used to explain the regioselectivity for the formation of compound 6, and the theoretical results agree well with the experimental results. Molecular docking and molecular dynamics confirmed the empirical test results and confirmed the stability of the complex during inhibition of the anti-apoptotic protein for killing cancer cells. Communicated by Ramaswamy H. Sarma.

New bis-isoxazole with monoterpenic skeleton: regioselective synthesis, spectroscopic investigation, electrochemical, and density functional theory (DFT) studies.

A novel bis-isoxazole was synthesized from (R)-Carvone and p-methylbenzaldoxime, via two successive [3+2] cycloaddition reactions (32CA). The newly obtained bis-isoxazole has been fully characterized by HRMS and NMR spectroscopy. The HMBC experiment was performed to determine the stereo and the regioselectivity of the reaction. The electrochemical behavior of the studied compound, in oxidation and reduction processes, was examined using the cyclic voltammetry technique. In addition, the regioselectivity of the [3+2] cycloaddition reaction and the molecular structure of the title compound was performed by density functional theory (DFT). The HOMO and LUMO orbitals were investigated to determine the electronic properties of the synthesized compound. Besides, the global reactivity indexes were used to explain the regioselectivity for the formation of the bis-isoxazole, the theoretical results are in good agreement with experimental findings.

Electronic investigation and spectroscopic analysis using DFT with the long-range dispersion correction on the six lowest conformers of 2.2.3-trimethyl pentane.

The conformational stability and internal rotation barriers, HOMO-LUMO gap and related properties, molecular static polarizability and hyperpolarizability parameters, and the NBO delocalization energies associated with the internal charge transfer (ICT) of 2.2.3-trimethylpentane in the ground state were carried out taking into account the long range dispersion correction through CAM-B3LYP and WB97XD levels at aug-cc-pvtz basis set. The six lowest conformations were differentiated by a deep and multiple spectroscopic investigation. The ultraviolet-visible (UV-Vis) absorption bands are assigned using molecular orbital data obtained by TD-WB97XD/aug-cc-pvtz calculations, and carbon 13C NMR signal peaks have been assigned using GIAO-WB97XD/aug-cc-pvtz method. In addition, the normal mode calculations of the most and less stable conformers using a scaled force field in terms of non-redundant local symmetry coordinates have been confronted to the experimental vibrational spectra temperature dependency.

Ab initio study on the six lowest energy conformers of iso-octane: conformational stability, barriers to internal rotation, natural bond orbital and first-order hyperpolarizability analyses, UV and NMR predictions, spectral temperature sensitivity, and scaled vibrational assignment.

In this paper, we present the quantum electronic study of iso-octane, based on MP2 and B3LYP methods using the 6-311++G(d,p) basis set. In addition to conformational stability and internal rotation barriers studies, the delocalization energies associated with the internal charge transfer (ICT) within each of the six lowest energy conformers were evaluated using NBO analysis. With the aim to differentiate even more between these conformers, the energy gap between HOMO and LUMO orbitals, chemical softness, and first-order hyperpolarizability (nonlinear optics property) were evaluated. Similarly, their spectral behavior was investigated at different levels; the ultraviolet (UV) absorption bands were assigned using molecular orbitals data obtained by TD-B3LYP calculations with 6-311++G(d,p) basis set, while carbon 13C NMR and proton 1H signal peaks were assigned using the GIAO-B3LYP/6-311++G(d,p) method. In addition, the normal mode calculations of the most and least stable conformers using a scaled force field in terms of nonredundant local symmetry coordinates were carried out to approach the vibrational spectra temperature dependency.