Discovery of Amide-Functionalized Benzimidazolium Salts as Potent α-Glucosidase Inhibitors

α-Glucosidase inhibitors (AGIs) are used as medicines for the treatment of diabetes mellitus. The α-Glucosidase enzyme is present in the small intestine and is responsible for the breakdown of carbohydrates into sugars. The process results in an increase in blood sugar levels. AGIs slow down the digestion of carbohydrates that is helpful in controlling the sugar levels in the blood after meals. Among heterocyclic compounds, benzimidazole moiety is recognized as a potent bioactive scaffold for its wide range of biologically active derivatives. The aim of this study is to explore the α-glucosidase inhibition ability of benzimidazolium salts. In this study, two novel series of benzimidazolium salts, i.e., 1-benzyl-3-{2-(substituted) amino-2-oxoethyl}-1H-benzo[d]imidazol-3-ium bromide 9a-m and 1-benzyl-3-{2-substituted) amino-2-oxoethyl}-2-methyl-1H-benzo[d] imidazol-3-ium bromide 10a-m were screened for their in vitro α-glucosidase inhibitory potential. These compounds were synthesized through a multistep procedure and were characterized by 1H-NMR, 13C-NMR, and EI-MS techniques. Compound 10d was identified as the potent α-glucosidase inhibitor among the series with an IC50 value of 14 ± 0.013 μM, which is 4-fold higher than the standard drug, acarbose. In addition, compounds 10a, 10e, 10h, 10g, 10k, 10l, and 10m also exhibited pronounced potential for α-glucosidase inhibition with IC50 value ranging from 15 ± 0.037 to 32.27 ± 0.050 µM when compared with the reference drug acarbose (IC50 = 58.8 ± 0.12 μM). A molecular docking study was performed to rationalize the binding interactions of potent inhibitors with the active site of the α-glucosidase enzyme.