2-Oxo-1,2,3,4-tetrahydropyrimidines Ethyl Esters as Potent β-Glucuronidase Inhibitors: One-pot Synthesis, In vitro and In silico Studies

Background: Glucuronidation is essential for the metabolism and excretion of toxic substances. β-Glucuronidase enzyme slows down the process of glucuronidation, and thus plays an important role in the on-set of colorectal carcinoma, and many other diseases. Inhibition of β- glucuronidase activity is thus identified as an important approach for the treatment of several diseases. Objective: Current study was aimed to synthesize a library of 2-oxo-1,2,3,4-tetrahydropyrimidine and to evaluate their β-glucuronidase inhibitory activity, and their mode of enzyme inhibition. Method: We synthesized a series of 2-oxo-1,2,3,4-tetrahydropyrimidines 1-25 by fusing urea, ethyl acetoacetate, and a variety of aldehydes using copper nitrate trihydrate as catalyst. All synthesized compounds were evaluated for their in vitro β-glucuronidase inhibitory activity. In addition, molecular docking studies were also performed by using MOE docking tools. Results: Eighteen compounds showed inhibitory activity better than the standard D-saccharic acid 1,4-lactone, a well known β-glucuronidase inhibitor (IC50 = 45.75 ± 2.16 μM). Compound 20 (IC50 = 1.36 ± 0.03 μM) showed an excellent inhibitory activity, thirty-five folds superior to the standard. Docking results highlighted the role of various chemical moieties at different positions on 2- oxo-1,2,3,4-tetrahydropyrimidine skeleton in enzyme inhibitory activity. Conclusion: This study has identified a class of potent β-glucuronidase inhibitors with the potential to be investigated further.