RESUMO
Bis(benzimidazol-2-yl)amine scaffold is not present in dipeptidyl peptidase-4 (DPP-4) inhibitors published so far. Herein, the inhibitory potential of bis(benzimidazol-2-yl)amine derivatives against DPP-4 was evaluated. In non-competitive inhibition mode, three representatives 5, 6, and 7 inhibited DPP-4 in vitro with IC50 values below 50 µM. The assessed binding pocket of DPP-4 for these benzimidazoles includes the S2 extensive subsite's residues Phe357 and Arg358. None of the lead compounds showed cytotoxicity to human neuroblastoma SH-SY5Y cells at concentrations lower than 10 µM. None showed significant binding affinity for dopamine D2, D3, and histamine H1, H3 receptors, at concentrations lower than 10 µM, leading to preferable outcomes due to mutually opposite effects of these neurotransmitters on each other. The potential beneficial effects on dopamine synthesis and the survival of dopaminergic neurons could be mediated by DPP-4 inhibition. These effective noncompetitive DPP-4 inhibitors, with inhibitory potential better than reference diprotin A (relative inhibitory potency compared to diprotin A is 3.39 and 1.54 for compounds 7 and 5, respectively), with the absence of the cytotoxicity to SH-SY5Y cells, are valuable candidates for further evaluation for the treatment of diabetes and associated disruption of neuronal homeostasis.
