Chitosan-based Schiff base polymer derived from acetyl triazolyl uracil: Synthesis, characterization, evaluation of antimicrobial and antioxidant activities, and density functional theory calculations

Abstract

This work aimed to synthesize a new acetyl triazolyl uracil (UT) compound and subsequently utilize it to obtain a new chitosan-based Schiff base polymer (CH-UT). The new derivative was characterized using elemental analysis, FTIR, ¹H NMR, XRD, TGA, DSC, and SEM analyses. Both UT and CH-UT were evaluated for their antibacterial activities against various Gram-positive and Gram-negative bacteria. The results demonstrated that the CH-UT displayed significant antibacterial activity against E. coli and L. monocytogenes, with inhibition ability of 44 % and 53 %, respectively, and low minimum inhibitory concentration (MIC) values of 31 μg/mL for E. coli and 15 μg/mL for L. monocytogenes. Additionally, the biofilm inhibitory activity showed that chitosan alone reduced E. coli biofilms by 10.25 %, whereas the combination of chitosan with UT in CH-UT increased inhibition to 43.00 %. The maximum biofilm inhibition for S. aureus was 42.02 % with UT alone, surpassing both chitosan and CH-UT. Furthermore, the CH-UT derivative showed notable antioxidant activity, with a value of 72.76 %. Results from frontier molecular orbitals (FMOs) analysis indicated that CH-UT exhibits higher reactivity due to its lower HOMO-LUMO energy gap and modified structure. The triazole group in CH-UT contributes to its potential antibacterial activity through hydrogen bonding and electronic properties.