Kundan Tayade

In this study, novel benzopyrazine-based motif 2-((2,3-bis(4-bromophenyl)quinoxalin-6-yl)(phenyl)-methylene)-1-((2,3-bis(4-bromophenyl)-quinoxalin-7-yl)(phenyl)methylene)hydrazine (compound 2) was synthesized and characterized. Among the tested microbes, compound 2 has demonstrated potent activity against the bacterial strains B. subtilis and B. megaterium (with MICs of 31.25 and 15.62, respectively), as well as the fungal strains R. oryzae, P. chrysogenum and A. niger (with MICs of 31.25, 62.5 and 62.5, respectively). Compound 2 (1 mg/mL) was also found to be a potent DPPH-reducing agent as compared to ascorbic acid. In vitro hemolytic assay revealed negligible activity (within 5% permissible limit) as compared to positive control Triton-X 100. Molecular docking studies indicated that compound 2 binds to the GyrB ATP-binding site through hydrogen bonds, hydrophobic interactions, and π-cation interactions, demonstrating favourable in silico interaction energy scores. Exploration of DFT shows that HOMO & LUMO are mainly located around the benzene rings and nitrogen atoms rather than bromine.

The hydrazine derivatives are known to possess several biological activities including anticancer, antibacterial and anti-fungal, anticonvulsant, and antioxidant. This communication presents the synthesis, X-ray crystal structure analysis, DFT calculations, cell cytotoxicity, and antioxidant activity of the Schiff base 4,4′-((1E,1′E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (compound 2). We have also isolated the side product compound 1 and characterized it using single X-ray crystallography. The crystal structure of compound 1 depicts that the ensuing C–H···N hydrogen bonding interaction is presented and discussed herein. In addition, the calculations using density functional theory (DFT) approximation supported by experimental ¹H and ¹³C NMR studies on the key compound 2 are reported. The results of theoretical and experimental ¹H and ¹³C NMR were concordant. The antioxidant activity of compound 2 was determined by using 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS^•+) radical cation assays and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. Compound 2 demonstrated excellent antioxidant activity in ABTS assay (IC₅₀ = 4.30 ± 0.21 µM) and DPPH assay (IC₅₀ = 81.06 ± 0.72 µM) with almost no cytotoxicity below 25 µM.

We have developed a novel isonicotiamide-based fluorescent “turn-on” chemosensor 1 for the selective detection of Zn²⁺ and HSO₄⁻.