Design, synthesis, inhibitory activity, and molecular simulations study for d-glucose-conjugated thioureas containing pyrimidine ring as multitarget inhibitors against α-amylase, α-glucosidase, DDP-4, and PTP1B in Type 2 diabetes mellitus†

A series of tetra-O-acetyl-α-D-glucopyranosyl thioureas 8a–l of substituted 2-aminopyrimidines 4a–l have been designed and synthesized. The latter were prepared from corresponding chalcones 3a–l of p-bromoacetophenone and appropriate substituted benzaldehydes by their reaction with guanidine. The target thiourea compounds 8a–l exhibited significant inhibitory activity in vitro against enzymes that were related to type 2 diabetes mellitus, including α-amylase, α-glucosidase, DPP-4, and PTP1B. Amongst these thioureas, compound 8k with an ortho-methoxy group was the most potential enzyme inhibitor against α-amylase with an IC₅₀ value of 9.72 ± 0.34 μM. Its meta-isomer 8j was the strongest inhibitor against α-glucosidase with IC₅₀ = 9.73 ± 0.72 μM. In the inhibition against DPP-4, compound 8f with a para-bromo substituent exhibited the strongest activity with an IC₅₀ value of 2.53 ± 0.03 nM. In the inhibition against PTP1B, compound 8h with a para-isopropyl substituent had the strongest inhibitory activity with an IC₅₀ value of 2.74 ± 0.03 μM. The enzyme kinetics of the most active compounds, including 8j, 8f and 8h against α-glucosidase, DPP-4, and PTP1B, respectively, were studied. The obtained results showed that 8j was a competitive α-glucosidase inhibitor with an inhibitory constant K_I value of 9.31 μM. Compound 8f was a non-competitive inhibitor for DDP-4 with an inhibitory constant K_I value of 12.57 μM. Compound 8h was also a non-competitive inhibitor for DDP-4 with an inhibitory constant K_I value of 12.41 μM. The cytotoxicity of the most active compounds, including 8f and 8k (against α-amylase), 8i and 8j (against α-glucosidase), 8a, 8f, and 8g (against DPP-4), and 8d, 8f, and 8h (against PTP1B) was screened. The obtained cytotoxicity showed that all tested inhibitors were noncytotoxic to human normal cell line 3T3. Induced fit docking simulations of all synthesized compounds 8a–l were performed on four enzymes 4W93 (for α-amylase), 3TOP (for α-glucosidase), 3W2T (for DPP-4), and 1NNY (for PTP1B). Key interactions of each of these ligands with residues in the active pocket of each studied enzyme have been shown.