Thiazolidine-2,4-dione hybrids as dual alpha-amylase and alpha-glucosidase inhibitors: design, synthesis, in vitro and in vivo anti-diabetic evaluation†

Twelve 3,5-disubstituted-thiazolidine-2,4-dione (TZD) hybrids were synthesized using solution phase chemistry. Continuing our previous work, nine O-modified ethyl vanillin (8a–i) derivatives were synthesized and reacted with the TZD core via Knoevenagel condensation under primary reaction conditions to obtain final derivatives 9a–i. Additionally, three isatin–TZD hybrids (11a–c) were synthesized. The intermediates and final derivatives were characterized using ¹H and ¹³C NMR spectroscopy, and the observed chemical shifts agreed with the proposed structures. The in vitro alpha-amylase and alpha-glucosidase inhibitory evaluation of newly synthesized derivatives revealed compounds 9F and 9G as the best dual inhibitors, with IC₅₀ values of 9.8 ± 0.047 μM for alpha-glucosidase (9F) and 5.15 ± 0.0017 μM for alpha-glucosidase (9G), 17.10 ± 0.015 μM for alpha-amylase (9F), and 9.2 ± 0.092 μM for alpha-amylase (9G). The docking analysis of synthesized compounds indicated that compounds have a higher binding affinity for alpha-glucosidase as compared to alpha-amylase, as seen from docking scores ranging from −1.202 to −5.467 (for alpha-amylase) and −4.373 to −7.300 (for alpha-glucosidase). Further, the molecules possess a high LD₅₀ value, typically ranging from 1000 to 1600 mg kg⁻¹ of body weight, and exhibit non-toxic properties. The in vitro cytotoxicity assay results on PANC-1 and INS-1 cells demonstrated that the compounds were devoid of significant toxicity against the tested cells. Compounds 9F and 9G showed high oral absorption, i.e., oral absorption >96%, and their molecular dynamics simulation yielded results closely aligned with the observed docking outcomes. Finally, compounds 9F and 9G were evaluated for in vivo antidiabetic assessment by the induction of diabetes in Wistar rats using streptozotocin. Molecule 9G has been identified as the most effective anti-diabetic molecule due to its ability to modulate several biochemical markers in blood plasma and tissue homogenates. The results were further confirmed by histology investigations conducted on isolated pancreas, liver, and kidney.