Sulfonamide-Based 2-Amino-1,3,4-Oxadiazole Derivatives as Dual Cholinesterase and Carbonic Anhydrase Inhibitors: Design, Synthesis, Kinetic Characterization, Molecular Modeling, and ADMET Evaluation.

In this study, 12 novel sulfonamide derivatives incorporating 2-amino-1,3,4-oxadiazole and 1,3-benzazol-2(3H)-one scaffolds were synthesized and structurally characterized using 1H NMR, 13C NMR, and LC-MS analyses. Their inhibitory activities were evaluated against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carbonic anhydrase I and II (CA I and CA II), and α-glucosidase. Owing to their potent inhibitory profiles, enzyme kinetic studies were performed to determine inhibition constants (Ki) and inhibition mechanisms. The synthesized compounds exhibited potent nanomolar cholinesterase inhibition. Compound 5b was identified as the most active AChE inhibitor (IC50 = 32.6 ± 2.6 nM; Kᵢ = 7.1 ± 0.6 nM), acting through a competitive inhibition mechanism, whereas compound 5g showed the strongest BChE inhibition (IC50 = 34.6 ± 2.8 nM; Kᵢ = 8.4 ± 0.8 nM) with a mixed-type inhibition profile. The derivatives also displayed significant carbonic anhydrase inhibition, with compound 6d emerging as the most potent inhibitor, particularly against CA II (IC50 = 0.9 ± 0.06 μM; Kᵢ = 0.43 ± 0.037 μM), while exhibiting competitive inhibition and strong activity against both CA isoforms. In contrast, α-glucosidase inhibition was generally weak, with compound 5d showing the highest activity (IC50 = 250.5 ± 21.32 μM). Molecular docking studies revealed favorable binding interactions within the catalytic sites of cholinesterase and carbonic anhydrase enzymes, while 200 ns length molecular dynamics simulations confirmed the stability of representative protein-ligand complexes. In silico ADMET and drug-likeness predictions using SwissADME and pkCSM indicated generally acceptable oral drug-likeness. Compound 6c exhibited the most balanced predicted pharmacokinetic profile, whereas 6d, despite its excellent enzyme inhibition, showed potential limitations associated with higher polarity, limited predicted blood-brain barrier penetration, and predicted toxicity risks. Overall, these findings identify the synthesized sulfonamide derivatives as promising scaffolds for the further development of multifunctional cholinesterase and carbonic anhydrase inhibitors.