Imidazole-2-thione and Acylhydrazone Derivatives Targeting Carbonic Anhydrase-II: Synthesis, In-Vitro Evaluations, and MM-GBSA Calculation.

Introduction: Several pathological conditions, including glaucoma, malignant brain tumors, and renal, gastric, and pancreatic carcinomas, are commonly associated with carbonic anhydrase type II (CA-II). Additionally, CA-II plays a critical role in regulating bicarbonate concentration in the eyes. The inhibition of CA-II reduces aqueous humor production and thus lowers intraocular pressure associated with glaucoma.

Objectives: This study aimed to synthesize potent CA-II inhibitors, 5-nitro-1H-benzo[ d]imidazole-2(3H)-thione (5NBIT) and acylhydrazone derivatives (1-13).

Methods: In this study, a new series of potent CA-II inhibitors, 5-nitro-1H-benzo[d]imidazole- 2(3H)-thione (5NBIT) and acylhydrazone derivatives (1-13), were synthesized and characterized by IR, NMR, UV and mass spectroscopy and evaluated against bovine carbonic anhydrase-II (bCA-II).

Results: Interestingly, most of the compounds showed better inhibition than the standard drug, acetazolamide (IC50: 18.2±0.51 μM), such as compounds 1 (IC50: 10.5±0.81 μM), 2 (IC50: 11.3±0.36 μM), 3 (IC50: 16.5±0.53 μM), 4 (IC50: 15.8±1.02 μM), 5 (IC50: 13.7±1.03 μM), and 9 (IC50: 12.2±1.03 μM). Among the synthesized compounds, compound 7 (IC50: 8.2±0.32 μM) exhibited the highest and compound 6 (IC50: 27.6±0.39 μM) showed the lowest inhibition. Structure-activity relationships suggest that the presence of nitro group on the phenyl ring contributed significantly to the overall inhibitory activity. Molecular docking of all the active compounds was performed to predict their binding behavior, which indicated good agreement between docking and experimental findings. Moreover, the MD simulation of compound 7 also showed excellent binding behavior and binding energy within the binding cavity of bCA-II.

Conclusion: These findings suggest that the synthesized 5NBIT and acylhydrazone derivatives exhibited potent CA-II inhibition, with several compounds outperforming the standard drug acetazolamide. These results provide valuable insights for the development of novel CA-II inhibitors with potential therapeutic applications in glaucoma and other related conditions.