The first outbreak in Wuhan, China, in December 2019 was reported about severe acute coronaviral syndrome 2 (SARS-CoV-2). The global coronavirus disease 2019 (COVID-19) pandemic in 2020 resulted in an extremely high potential for dissemination. No drugs are validated in large-scale studies for significant effectiveness in the clinical treatment of COVID-19 patients, despite the worsening trends of COVID-19. This study aims to design a simple and efficient cyclo-condensation reaction of 6-aminouracil derivatives 2a–e and isatin derivatives 1a-c to synthesize spiro-oxindoles 3a–d, 4a–e, and 5a–e. All compounds were tested in vitro against the SARS-CoV-2. Four spiro[indoline-3,5’-pyrido[2 ,3-d:6,5-d’]dipyrimidine derivatives 3a, 4b, 4d, and 4e showed high activities against the SARS-CoV-2 in plaque reduction assay and were subjected to further RNA-dependent-RNA-polymerase (RdRp) and spike glycoprotein inhibition assay investigations. The four compounds exhibited potent inhibitory activity ranging from 40.23 ± 0.09 to 44.90 ± 0.08 nM and 40.27 ± 0.17 to 44.83 ± 0.16 nM, respectively, when compared with chloroquine as a reference standard, which showed 45 ± 0.02 and 45 ± 0.06 nM against RdRp and spike glycoprotein, respectively. The computational study involving the docking studies of the binding mode inside two proteins ((RdRp) (PDB: 6m71), and (SGp) (PDB: 6VXX)) and geometrical optimization used to generate some molecular parameters were performed for the most active hybrids.
3,5-Diamino-4-(3-trifluoromethylphenyldiazenyl)-1H-pyrazole was used as a starting scaffold for the synthesis of new pyrazole-based heterocycles to study their effects on the proliferation of three human cancer cell lines; human liver carcinoma cell line (HepG-2), colon cancer cell line (HCT-116) and human breast cancer cell line (MCF-7) using MTT assay. The synthesized compounds were characterized on the basis of IR, H NMR,C NMR, mass spectral data and elemental analysis results. Cytotoxicity assay results revealed that some of the compounds showed potent growth inhibition against all the cell lines tested, with IC50 values in the range of 0.64-7.73 μg/mL. Breast cancer cells were used for further detailed studies to understand the mechanism of cell growth inhibition and apoptosis-inducing effect of the most active compounds. The results indicated that compounds 3a, 10b and 11a arrested MCF-7 cells at G2/M phase of the cell cycle and might induce apoptosis via caspase-3-dependent pathway. Molecular modeling and binding mode analysis of the most active compounds to caspase 3 active site further provide a synergistic mechanism for their pro-apoptotic effects. In order to explore the structural requirements controlling the observed cytotoxic properties, 3D pharmacophore model was generated.
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