Design, Synthesis and Antibacterial Evaluation of (Z)-3-Methyl-2-Oxo-N-(2-((1-phenylethylidene) amino)ethyl)-1,2-Dihydroquinoxaline-6-Sulfonamide Derivatives

Abstract

Background: Multidrug-resistant bacteria continue to create a need for new antibacterial scaffolds, and quinoxaline-sulfonamide derivatives are of interest because of their reported biological activity. Aim: This study synthesised and characterised a series of (Z)-3-methyl-2-oxo-N-(2-((1-phenylethylidene)amino)ethyl)-1,2-dihydroquinoxaline-6-sulfonamide derivatives and evaluated their antibacterial activity against selected bacterial strains. Methods: The target derivatives were prepared by condensation of N-(2-aminoethyl)-3-methyl-2-oxo-1,2-dihydroquinoxaline-6-sulfonamide with substituted aromatic ketones. The products were obtained in moderate to high yields. The synthesised compounds were characterised using FT-IR, ¹H-NMR and ¹³C-NMR spectroscopy. Antibacterial activity was assessed by agar-well diffusion, followed by determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results: All synthesised compounds showed activity against the 10 bacterial strains evaluated. The reported MIC values ranged from 0.0781 to 0.625 mg/mL. The study also reported bactericidal activity based on the MBC assessment, with activity varying among the compounds and test organisms. The findings indicate that structural variation within the synthesised series influenced antibacterial performance under the assay conditions. Conclusion: The synthesised quinoxaline-sulfonamide Schiff bases demonstrated antibacterial activity against the selected Gram-positive and Gram-negative bacterial strains. These results support further investigation of this compound series as a basis for developing and optimising antibacterial candidates.