Discovery of new thiazolo[4,5-b] pyridine-based 1,2,3-triazoles as potent antioxidant agents: <i>in vitro</i> and <i>in silico</i> investigation

A new set of thiazolopyridine-carbonitrile derivatives containing 1,2,3-triazole structures ( 9a-j ) was synthesized through a 2-step process. First, thiazolopyridine-carbonitriles underwent propargylation, followed by a copper-catalyzed reaction (CuAAC) with various substituted phenyl azides to form the triazole rings. The heterocyclic hybrid molecules were comprehensively characterized by spectral analysis (Nuclear magnetic resonance ( 1 H, 13 C-NMR), high-resolution mass spectrometry (HR-MS), Fourier-transform infrared (FT-IR)). The final products were evaluated for antioxidant activity using three 2,2-diphenyl-1-picrylhydrazyl radical (DPPH • ), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical (ABTS •+ ), and β-carotene-linoleic acid assays. Among the synthesized compounds, 9e and 9i exhibited significant antioxidant properties, effectively scavenging ABTS •+ radicals with IC 50 values of 18.52 ± 0.18 µM and 15.18 ± 0.25 µM, respectively. These results were comparable to, or even better than, the standard antioxidants Butylated Hydroxyanisole (BHA) and α-tocopherol (α-TOC) used as references. Additionally, 9i and 9e were shown to be comparatively more active in the lipid peroxidation inhibition assay, with respective values of (IC 50 = 09.10 ± 0.46 µM and 16.08 ± 0.18 µM). Additionally, docking simulations demonstrated that compounds 9e and 9i exhibit robust binding at both the nuclear factor erythroid 2–related factor 2 (NRF2)-kelch-like ECH-associated protein 1 (KEAP1) interface and the catalase heme-binding (HEM) site, with binding energies (in kcal/mol) of –9.3; –9.4 and –10.8; –11.0, respectively. The above compounds form critical hydrogen bonds with active residues of NRF2-KEAP1, such as ARG483, SER508, and SER555, alongside stabilizing π-interactions with TYR525 and ALA556. Their binding poses closely overlap with the reference inhibitor (3S)-3-(4-chloro-3-methylphenyl)-3-(1-methyl-1H-benzotriazol-5-yl)propanoic acid (J6Q), suggesting a similar mechanism of action and highlighting their potential as effective modulators of antioxidant defense mechanisms.