Synthesis, Comparative in vitro Antibacterial, Antioxidant & UV fluorescence studies of bis Indole Schiff bases and Molecular docking with ct-DNA & SARS-CoV-2 Mpro.

Singhal, Sugandha; Khanna, Pankaj; Khanna, Leena

In this study, synthesis of fifteen novel bis indole based Schiff bases (SBs) 4a-o was conducted by condensation of 2-(1-aminobenzyl)benzimidazole with symmetrical bis-isatins linked via five alkyl chains (n = 2, 3, 4, 5 and 6). These were subjected to ADME, physiochemical properties, molecular docking, in vitro antibacterial and antioxidant studies. The in silico studies indicated lower toxicity with metabolic stability for nearly all the derivatives proving reliability as drug candidates. The comparative antibacterial study against S. aureus and E. coli, also showed a superior inhibition than reference drug and their mono counterparts. The increase in linker alkyl chain length and variation of substituents in indole, further predicted increased inhibition, with maximum value for compound 4o at 50 μg ml-1 . The in vitro ct-DNA binding ability of compounds 4c, 4f, 4i, 4l, 4m, 4n, and 4o was evaluated via UV/Vis and Fluorescence spectroscopy techniques. A hyperchromic effect was observed with no apparent wavelength shift which predicted for the groove binding mode. A moderate binding constant for 4o, in fluorescence results, confirms groove binding. The molecular docking of 4o with ct-DNA (PDBID:1BNA) and SARS-CoV-2 Mpro (3CL protease, PDBID:6LU7) prove its efficacy as potential DNA binder and antiviral agent.