Phthalimide–benzoic acid hybrids as potent aldose reductase inhibitors: Synthesis, enzymatic kinetics, and in silico characterization

Abstract

Aldose reductase (ALR2; AKR1B1) is implicated in hyperglycemia-driven tissue injury and remains a tractable enzymatic target. We developed a concise, chromatography-free two-step route to phthalimide–benzoic acid hybrids (5a–5m) and profiled their biochemical activity against human ALR2. Across the series, halogenated analogs were most active, with the para-bromophenyl derivative 5d emerging as the top hit (K_I = 7.56 nM). Steady-state kinetic analysis indicated a competitive inhibition mechanism. Molecular docking to the ALR2 active site (PDB 4JIR), supported by MM-GBSA rescoring, yielded a catalytically consistent binding mode featuring hydrogen-bonding within the anion-binding region (Tyr48, His110) and complementary hydrophobic contacts (Trp111, Trp219), with Cys298 contributing as a proximal hydrophobic contact. In cell-based assays (A549, Hep3B, L929), the compounds generally showed low intrinsic cytotoxicity at the tested concentrations, suggesting a favorable preliminary safety margin aligned with their ALR2-directed pharmacology. In silico ADME/Tox assessments further supported oral drug-likeness. Overall, these results identify phthalimide–benzoic acid hybrids as tractable ALR2 inhibitor scaffolds that combine potent biochemical inhibition with a competitive kinetic profile and encouraging early safety signals, warranting in vivo evaluation and SAR-guided optimization.