Novel Benzo[4,5]imidazo[1,2-a]pyrimidine derivatives as selective Cyclooxygenase-2 Inhibitors: Design, synthesis, docking studies, and biological evaluation

Design, Synthesis, In vitro and In vivo Evaluation of New Imidazo[1,2-a]pyridine Derivatives as Cyclooxygenase-2 Inhibitors

BACKGROUND

Cyclooxygenase-2 (COX-2), the key enzyme in the arachidonic acid conversion to prostaglandins, is one of the enzymes associated with different pathophysiological conditions, such as inflammation, cancers, Alzheimer's, and Parkinson's disease. Therefore, COX-2 inhibitors have emerged as potential therapeutic agents in these diseases.

OBJECTIVE

The objective of this study was to design and synthesize novel imidazo[1,2-a]pyridine derivatives utilizing rational design methods with the specific aim of developing new potent COX-2 inhibitors. Additionally, we sought to investigate the biological activities of these compounds, focusing on their COX-2 inhibitory effects, analgesic activity, and antiplatelet potential. We aimed to contribute to the development of selective COX-2 inhibitors with enhanced therapeutic benefits.

METHODS

Docking investigations were carried out using AutoDock Vina software to analyze the interaction of designed compounds. A total of 15 synthesized derivatives were obtained through a series of five reaction steps. The COX-2 inhibitory activities were assessed using the fluorescent Cayman kit, while analgesic effects were determined through writing tests, and Born's method was employed to evaluate antiplatelet activities.

RESULTS

The findings indicated that the majority of the tested compounds exhibited significant and specific inhibitory effects on COX-2, with a selectivity index ranging from 51.3 to 897.1 and IC50 values of 0.13 to 0.05 μM. Among the studied compounds, derivatives 5e, 5f, and 5j demonstrated the highest potency with IC50 value of 0.05 μM, while compound 5i exhibited the highest selectivity with a selectivity index of 897.19. In vivo analgesic activity of the most potent COX-2 inhibitors revealed that 3-(4-chlorophenoxy)-2-[4-(methylsulfonyl) phenyl] imidazo[1,2-a]pyridine (5j) possessed the most notable analgesic activity with ED50 value of 12.38 mg/kg. Moreover, evaluating the antiplatelet activity showed compound 5a as the most potent for inhibiting arachidonic acidinduced platelet aggregation. In molecular modeling studies, methylsulfonyl pharmacophore was found to be inserted in the secondary pocket of the COX-2 active site, where it formed hydrogen bonds with Arg-513 and His-90.

CONCLUSION

The majority of the compounds examined demonstrated selectivity and potency as inhibitors of COX-2. Furthermore, the analgesic effects observed of potent compounds can be attributed to the inhibition of the cyclooxygenase enzyme.

Synthesis of new imine-/amine-bearing imidazo[1,2-a]pyrimidine derivatives and screening of their cytotoxic activity

Imidazo[1,2-a]pyrimidine derivatives bearing imine groups (3a-e) were successfully synthesized in moderate to good yields using microwave-assisted heating. Corresponding amine derivatives (4a-e) were also obtained by the reduction reaction of the imine derivatives (3a-e). All synthesized products were characterized by FT-IR, 1H NMR, 13C NMR, and LC-MS spectroscopic techniques. In silico ADMET, Lipinski, and drug-likeness studies of the compounds were conducted and all were found to be suitable drug candidates. The cytotoxicity of the potential drug molecules was screened against the breast cancer cell lines MCF-7 and MDA-MB-231 and the healthy model HUVEC by the sulforhodamine B method. According to the antiproliferative studies, compounds 3d and 4d showed remarkable inhibition of MCF-7 cells with IC50 values of 43.4 and 39.0 μM and of MDA-MB-231 cells with IC50 values of 35.9 and 35.1 μM, respectively. In particular, compound 3d selectively inhibited the proliferation of MCF-7 1.6-fold and MDA-MB-231 2.0-fold relative to healthy cells. Moreover, the apoptotic mechanism studies indicated that compound 4d induced apoptosis by moderately increasing the ratio of Bax/Bcl-2 genes. Imidazo[1,2-a]pyrimidine derivative 3d, a promising cytotoxic agent, may be helpful in the discovery of new and more efficient anticancer agents for breast cancer treatment.