Design, Synthesis And Biological Evaluation Of New Substituted Heterocyclic Scaffolds As Potential Antimicrobial And Antioxidant Agents

Abstract

A series of novel substituted heterocyclic scaffolds were designed and synthesised through stepwise condensation and cyclisation reactions, by which structurally diverse derivatives were obtained in good yields. The synthesised compounds were characterised using spectroscopic techniques, including FT-IR, ¹H NMR, ¹³C NMR, and mass spectrometry, which confirmed heterocyclic ring formation and structural integrity. Biological evaluation was carried out to assess antimicrobial activity against selected Gram-positive and Gram-negative bacterial strains, as well as fungal strains, using standard in-vitro methods. Several compounds exhibited moderate to good inhibitory activity, where derivatives bearing electron-withdrawing substituents showed enhanced antimicrobial effects, particularly against Gram-positive bacteria. Antioxidant potential was evaluated using a DPPH free radical scavenging assay, which revealed concentration-dependent activity. Compounds containing electron-donating substituents demonstrated superior antioxidant performance, attributed to effective radical stabilisation. The study establishes a clear structure–activity relationship for antimicrobial and antioxidant activity, where substituent electronics govern antimicrobial and antioxidant responses. These findings highlight the potential of substituted heterocyclic frameworks as promising leads for further optimisation and biological investigation.