New isoxazoline‐linked 1,3,4‐thiadiazole derivatives: Synthesis, antiproliferative activity, molecular docking, molecular dynamics and DFT

Utilising (D)-Limonene as the starting material, this study reports the efficient synthesis of two series of isoxazoline derivatives linked with the 1,3,4-thiadiazole moiety. The synthesised compounds were obtained in good yields and characterised by ¹H- and ¹³C[sbnd]NMR spectroscopy, alongside high-resolution mass spectrometry (HRMS). Further anticancer evaluations were conducted against four human cancer cell lines (HT-1080, A-549, MCF-7, and MDA-MB-231) for the newly synthesised isoxazoline-1,3,4-thiadiazoles and their intermediate derivatives. Most of these compounds demonstrated moderate to potent antiproliferative activity. Notably, compounds 12c and 12b exhibited the highest activity, with IC₅₀ values ranging from 16.58± 1.49 µM to 17.76 ± 1.69 µM, respectively. Molecular modelling analyses were conducted to elucidate the findings from experimental wet-lab studies. Specifically, the affinity of the most potent synthesised compounds, 12b and 12c, towards caspase-3 and Bcl-2 was examined through molecular docking. The stability of the resultant complexes was assessed using molecular dynamics (MD) simulations. The docking analysis revealed that the active compounds exhibited greater binding affinity towards caspase-3. Furthermore, MD simulations indicated that the caspase-3–12c complex derived from the docking process might be the most stable among the investigated complexes. Additionally, density functional theory (DFT) was employed to examine the electronic and frontier molecular orbitals of the compounds, suggesting consistent chemical stability for analogous derivatives within the series.