Inhibition of iNOS by Benzimidazole Derivatives: Synthesis, Docking, and Biological Evaluations

Abstract

Background: Inducible nitric Oxide Synthase (iNOS) plays a key role in the progression of inflammatory diseases by accelerating the production of NO, which makes it an intriguing target to treat inflammation in complex diseases. Therefore, the search is on to develop molecules as selective iNOS inhibitors. Objective: The present work was aimed to design, synthesize and evaluate benzimidazole-coumarin coupled molecules as anti-iNOS agents through in silico and pharmacological studies. Methods: A critical study of literature reports on iNOS inhibitors led to the selection of a (un)substituted coumarin nucleus, 2-aminobenzimidazole, and a 4-atom linker as important structural components for iNOS inhibition. Two series of compounds (7-16 and 17-26) were designed and synthesized by coupling these components. The compounds were subjected to docking using iNOS (1QW4) and nNOS (1QW6) as targets. All compounds were evaluated for NO and iNOS inhibitory activities in vitro. The selected compound was finally evaluated for anti-inflammatory activity in vivo using the carrageenan-induced rat paw edema model. Results : All compounds showed moderate to good inhibition of NO and iNOS in vitro. Compound 12 was the most potent inhibitor of NO and iNOS. Hence, it was evaluated in vivo for toxicity and anti-inflammatory activity. It was found to be safe in acute toxicity studies, and effective in reducing the rat paw edema significantly. Its anti-inflammatory behaviour was similar to that of aminoguanidine, which is a selective iNOS inhibitor. Conclusion: The newly synthesized benzimidazole-coumarin hybrids may serve as potential leads for the development of novel anti-iNOS agents.

iNOS inhibitors: Benzimidazole-coumarin derivatives to combat inflammation

“…For the synthesis of the designed compounds, 5-(un)substituted-2-aminobenzimidazole intermediate (13a-e) was coupled with (un)substituted coumarin-based intermediates (7-8 and 11-12) by using the methods already reported in literature by our research group [9]. Intermediate 3 was procured commercially and used as such.…”

“…Several 3-substituted compounds were synthesized by our research group [9] to produce the target molecules. A suspension of dried potassium carbonate (2.5 mmol) and a solution of compounds 7 or 8 (0.5 mmol) in DMF (10 mL) was treated with 5-(un)substituted-2-aminobenzimidazole 13a-e (1 mmol).…”

“…Previously, our research team reported a method for preparing these compounds [9]. A solution of compounds 11 or 12 (0.25 mol) in THF (10 mL) was added to an excess of SOCl2 (2-5 mL) and allowed to heat at 40 °C for 30 min.…”

“…The tubes were incubated in a CO2 chamber for 24 h. Finally, Griess reagent was transferred in each test tube, the contents are mixed well, and the tubes are kept in the dark for 10 min. Each tube was shaken gently to mix the content, and the absorbance (OD) is read at 540 nm taking Griess reagent as blank [9,17,18]. NO inhibitory activity of the test and standard compounds was calculated using the Equation (1):…”

“…The compounds showing good potential in vitro are evaluated through an in vivo carrageenan-induced rat paw edema model using L-NAME and AG, respectively, as reference nonselective and selective iNOS inhibitors. Previously, our research group synthesized 3substituted coumarin derivatives as anti-iNOS agents [9]. To check the effect of orientation of -OH group of coumarin on biological activity, the current study was designed.…”