Design and Biological Profiling of a Drug-like Chloropyridine Diamine as a Dual Antioxidant–Antimicrobial Lead: In Vitro Evaluation and In Silico Multi-Target Studies

Abstract

Bacterial and fungal infections, together with oxidative stress-mediated damage, remain major challenges in human health and in the protection of materials, highlighting the need for new multifunctional molecules that combine antioxidant and antimicrobial properties. In this context, a new chloropyridine-based derivative, N4,N4-bis((6-chloropyridin-3-yl)methyl)-N1,N1-diethylpentane-1,4-diamine (AMZ), was synthesized via a simple, catalyst-free N-alkylation of N1,N1-diethylpentane-1,4-diamine with 2-chloro-4-(chloromethyl)pyridine in acetonitrile at 55 °C, affording a 62% yield. The structure of AMZ was confirmed by melting point determination, 1H and 13C NMR spectroscopy, and EI–MS analysis. Its antioxidant activity was evaluated using DPPH and FRAP assays with BHT as a reference standard, while antibacterial and antifungal activities were assessed via disk diffusion and microdilution methods to determine inhibition zones and MIC/MBC values. In silico investigations included drug-likeness and ADMET predictions, as well as molecular docking on catalase (PDB: 2CAG) and fungal CYP51 (PDB: 1EA1). AMZ exhibited dose-dependent radical scavenging in the DPPH assay, reaching 76.88 ± 3.20% inhibition at 1000 µg/mL, with an EC50 of 26.03 ± 0.21 µg/mL, close to that of BHT (23.65 ± 0.22 µg/mL). In the FRAP assay, AMZ showed a higher reducing power than BHT at a low concentration (OD50 µg/mL 0.177 ± 0.023 vs. 0.134 ± 0.017), although its FRAP EC50 was higher (700.48 ± 22.54 vs. 400.16 ± 8.67 µg/mL). AMZ displayed broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi, with particularly strong effects on Bacillus subtilis (44.5 ± 0.5 mm; MIC/MBC 0.008 mg/mL) and Aspergillus niger (30 mm; MIC/MBC 0.030 mg/mL), in some cases comparable or superior to streptomycin and fluconazole. In silico analysis indicated that AMZ fulfilled major drug-likeness rules, showed high predicted intestinal absorption (91.14%), and was classified as non-AMES toxic, while docking predicted favorable binding to catalase and CYP51, in agreement with the experimental antioxidant and antifungal activities. These findings highlight the potential of AMZ as a multi-target pyridine-based lead compound that warrants further structural optimization and in vivo evaluation for applications in oxidative-stress-related and infectious conditions.