Pyrrolidine-2-carbonitrile Derivatives as Multifunctional Antidiabetic Agents: Inhibition of α-Amylase, α-Glucosidase, and DPP-IV With Structure-Activity Relationships, HSA Binding, and Molecular Docking Studies

Abstract

A series of pyrrolidine-2-carbonitrile derivatives was designed, synthesized, and evaluated for their antidiabetic potential. The synthesized compounds exhibited notable inhibitory activity, with IC₅₀ values ranging from 9.36 to 21.54 µg/mL for α-amylase, 13.32 to 46.14 µg/mL for α-glucosidase, and 22.87 to 42.12 µg/mL for DPP-IV. Among the evaluated derivatives, compounds bearing para-methyl (6b) and para-chloro (6c) substituents demonstrated the most potent inhibitory activity across all three enzymatic targets. To elucidate the underlying trends, a SAR analysis was conducted, revealing that both electronic properties and steric effects of the substituents significantly influenced enzyme inhibition potency. The molecular docking studies showed strong and specific interactions between the active compounds and key residues within the catalytic sites of the target enzymes. In addition, UV-visible absorption and fluorescence spectroscopy studies demonstrated high binding affinities for both 6b and 6c with HSA, having binding constant (K_a) values of 7.31 × 10⁵ M⁻¹ and 7.43 × 10⁵ M⁻¹, respectively. Taken together, these findings highlight compounds 6b and 6c as promising lead candidates for the development of multitarget antidiabetic agents.