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[Display omitted] • Novel 2-phenyl-1 H -benzo[ d ]imidazole-based α-glucosidase inhibitors were identified. • Some of derivatives significantly increased α-glucosidase inhibition. • The non-competitive inhibitors 15o and 22d did not have cytotoxicity towards LO2 cells. • Compound 15o showed significant in vivo anti-hyperglycaemic activity. In the present study, a series of 2-phenyl-1 H -benzo[ d ]imidazole-based α-glucosidase inhibitors were synthesized and evaluated for their in vitro and in vivo anti-diabetic potential. Screening of an in-house library revealed a moderated α-glucosidase inhibitor, 6a with 3-(1 H -benzo[ d ]imidazol-2-yl)aniline core, and then the structural optimization was performed to obtain more efficient derivatives. Most of these derivatives showed increased activity than 6a , and the most promising inhibitors were found to be compounds 15o and 22d with IC 50 values of 2.09 ± 0.04 and 0.71 ± 0.02 µM, respectively. Fluorescence quenching experiment confirmed the direct binding of compounds 15o and 22d with α-glucosidase. Kinetic study revealed that both compounds were non-competitive inhibitors, that was consistent with the result of molecular docking studies where they located at the allosteric site of the enzyme. Cell viability evaluation demonstrated the non-cytotoxicity of 15o and 22d against LO2 cells. Furthermore, the in vivo pharmacodynamic study revealed that compound 15o showed significant hypoglycemic activity and improved oral sucrose tolerance, comparable to the positive control acarbose. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel tetrahydrobenzo[ b ]thiophen-2-yl)urea derivatives were designed and synthesized. • Tetrahydrobenzo[ b ]thiophen-2-yl)urea derivatives significantly increased α-glucosidase inhibition. • The most potent compounds 8r and 8s showed non-toxicity towards LO2 and HepG2 cells. • Compound 8r showed promising in vivo anti-hyperglycaemic activity. α-Glucosidase inhibitors, which can inhibit the digestion of carbohydrates into glucose, are one of important groups of anti-type 2 diabetic drugs. In the present study, we report our effort on the discovery and optimization of α-glucosidase inhibitors with tetrahydrobenzo[ b ]thiophen-2-yl)urea core. Screening of an in-house library revealed a moderated α-glucosidase inhibitors, 5a , and then the following structural optimization was performed to obtain more efficient derivatives. Most of these derivatives showed increased inhibitory activity against α-glucosidase than the parental compound 5a (IC 50 of 26.71 ± 1.80 μM) and the positive control acarbose (IC 50 of 258.53 ± 1.27 μM). Among them, compounds 8r (IC 50 = 0.59 ± 0.02 μM) and 8s (IC 50 = 0.65 ± 0.03 μM) were the most potent inhibitors, and showed selectivity over α-amylase. The direct binding of both compounds with α-glucosidase was confirmed by fluorescence quenching experiments. Kinetics study revealed that these compounds were non-competitive inhibitors, which was consistent with the molecular docking results that compounds 8r and 8s showed high preference to bind to the allosteric site instead of the active site of α-glucosidase. In addition, compounds 8r and 8s were not toxic (IC 50 > 100 μM) towards LO2 and HepG2 cells. Finally, the in vivo anti-hyperglycaemic activity assay results indicated that compounds 8r could significantly decrease the level of plasma glucose and improve glucose tolerance in SD rats treated with sucrose. The present study provided the tetrahydrobenzo[ b ]thiophen-2-yl)urea chemotype for developing novel α-glucosidase inhibitors against type 2 diabetes. [ABSTRACT FROM AUTHOR]