Imidazole-1,2,4-oxadiazole-piperazine hybrids as potent anticancer agents: Synthesis, biological evaluation and...

A series of novel imidazole integrated substituted 1,2,4-oxadiazoles coupled with piperazines were synthesized from 5-chloro-4-(p-tolyl)-1H-imidazole-2-carbonitrile through a three-step synthetic pathway, resulting in excellent yields. All 26 hybrid imidazole derivatives were purified and characterized using NMR and HRMS techniques. Their cytotoxic effects were evaluated against five distinct cancer cell lines: MDA-MB-231 (breast), MIA PaCa-2 (pancreatic), DU-145 (prostate), HEP-G2 (liver), and HCT-116 (colorectal) utilizing the SRB assay. Compound 5w demonstrated the highest antiproliferative activity, with low IC₅₀ values ranging from 7.51 ± 1.1 to 33.67 ± 1.4 µM across all evaluated cancer cell lines, whereas it exhibited less cytotoxicity in the normal human embryonic kidney epithelial cells (HEK-293T). Furthermore, compounds 5k, 5o, 5p, and 5q displayed selective cytotoxicity towards MDA-MB-231, while 5y showed anticancer activity exclusively in HEP-G2. Morphological assessments of 5w treated cell lines showed rounding of the cells and cell death. Flowcytometric cell cycle analysis revealed that 5w significantly increased the percentage of G2/M phase cells, indicating the G2/M cell cycle arrest in MDA-MB-231, MIA PaCa-2 and DU-145. Further, Western blot analysis strengthened that the potent compound 5w induced the G2/M cell cycle arrest, 5w treatment decreased the key cell cycle proteins CDK1, CDK2, and Cyclin B1 in a dose-dependent manner. Moreover, molecular docking studies indicated strong interactions between 5w and inhibitor of differentiation/DNA-binding proteins, highlighting its potential as a promising candidate for anticancer drug development.