Synthesis of Enduracididine Free Linear Teixobactin Analogs:Molecular Docking, DFT Calculations, and Their AntimicrobialActivities, Bacterial Cell Wall Lysis and Glucose Assay

Introduction: Teixobactin (TX) is a new class of antibiotics with a unique structure and strong efficacy against gram-positive bacteria. It is a "head-to-side-chain" cyclodepsipeptide with considerable potential as a lead molecule for creating novel antibiotics to combat multidrug-resistant pathogens. Methods: In this study, we systematically design, synthesize, and evaluate modified Teixobactin analogs (TX1-TX5) for antimicrobial activity. This study presents a novel peptide derived from linearized Teixobactin, with amino acid substitutions at aa1 (N-Me-D-Phe-OH), aa5 (HL- allo-Ile-OH), and the exclusion of L-allo-Enduracididine at aa10, synthesized using solidphase peptide synthesis. We employed various software tools, including Molinspiration and SwissADME, to estimate the pharmacokinetic features of the synthesized TX analogs. Molecular docking studies were performed using AutoDock Vina, and PyMOL and Biovia Discovery Studio visualizer were utilized to visualize the protein-ligand interactions. The molecular structures of TX and TX analogs were modeled using the Sinapsis software. Results: Antimicrobial susceptibility tests against Staphylococcus aureus, Bacillus subtilis, E. coli, Pseudomonas sp., Aspergillus niger, and Fusarium sp. identified novel TX analogs exhibiting strong bactericidal and fungicidal activity at 80 μg/mL. Bacterial cell wall lysis assays confirmed significant cell wall breakdown upon TX analog treatment. Glucose assay results indicate reduced glucose uptake in bacterial cells treated with TX analogs. Docking studies revealed that the synthesized TX analogs exhibited good binding affinity, ranging from -5.0 to - 12.5 kcal/mol, compared with bacterial and fungal proteins, as well as the Delafloxacin and Ketoconazole standards. Density Functional Theory (DFT) computations were employed to investigate chemical reactivity descriptors. Discussion: In-vitro studies indicated that TX1 and TX3 showed excellent bactericidal activity by forming inhibition zone diameters (mm) from 6.49 ±0.31 to 11.50 ±0.59 at 70 and 80 μg/mL concentrations against Staphylococcus aureus, Bacillus subtilis, E. coli, and Pseudomonas sp., compared to the standards Streptomycin (+ve) and DMSO (-ve). The TX2, TX3, and TX5 exhibit excellent fungicidal activity with inhibition zone diameters (mm) from 7.23 ±0.25 to 10.23 ±0.30 at 70 and 80 μg/mL concentrations against Aspergillus niger and Fusarium sp., compared to the standards ketoconazole (+ve) and DMSO (-ve). The bacterial cells treated with TX1 displayed more dead cells than the control in all bacterial strains, indicating excellent cell lysis. Conclusion: Mass, 1H NMR, and HPLC analysis characterized the synthesized fine TX analogs (TX1-TX5). The DFT and docking studies' electronic characteristic calculations predicted that halogenated (TX1, TX2, and TX4) and methoxy (TX3) substituted analogs have higher stability and electrophilicity, making them suitable agents for antimicrobial activity.