Pyrazole-thiazolidine hybrids as α-amylase inhibitor: a mechanistic and computational investigation

The development of therapeutic agents with dual bioactivity represents a promising strategy in modern drug discovery. In this study, we report the design, synthesis, and characterization of a novel series of pyrazole-thiazolidine hybrids (5a-f). The chemical structures of all synthesized compounds were unequivocally confirmed through comprehensive spectroscopic analysis. The entire series was evaluated for its in vitro biological potential, specifically as antidiabetic agents via α-amylase inhibition and as anticancer agents via cytotoxicity against the PC3 human prostate cancer cell line. In the α-amylase assay, compound 5d, bearing a para-nitro substituent, emerged as the most potent inhibitor with an IC₅₀ value of 15.90 ± 0.88 µg/mL, demonstrating activity nearly equipotent to the standard drug Acarbose. Conversely, in the anticancer screening, compound 5f, with a meta-hydroxyl group, displayed the highest cytotoxicity against PC3 cells (IC₅₀ = 108.39 ± 0.95 µg/ml). A striking divergent Structure-Activity Relationship (SAR) was observed: para-electron-withdrawing groups were optimal for α-amylase inhibition, whereas meta-substitution was critical for anticancer activity. To rationalize these findings, comprehensive computational studies were performed. Molecular docking revealed distinct binding modes and interaction patterns for each biological target, which strongly correlated with the experimental results. Furthermore, 100-nanosecond molecular dynamics (MD) simulations on the most potent α-amylase inhibitors (5c and 5d) confirmed the formation of exceptionally stable protein-ligand complexes, elucidating the dynamic mechanism of inhibition at an atomic level. These results establish the pyrazole-thiazolidine scaffold as a highly promising and "tunable" chemotype for the development of novel therapeutic agents.