Synthesis of novel piperazine-based bis(thiazole)(1,3,4-thiadiazole) hybrids as anti-cancer agents through caspase-dependent apoptosis.

A series of novel piperazine-based bis(thiazoles) 13a-d were synthesized in moderate to good yields via reaction of the bis(thiosemicarbazones) 7a, b with an assortment of C-acetyl-N-aryl-hydrazonoyl chlorides 8a-f. Similar treatment of the bis(thiosemicarbazone) 7a, b with C-aryl-N-phenylhydrazonoyl chlorides 10a, b afforded the expected bis(thiadiazole) based piperazine products 13b-d in reasonable yields. Cyclization of 7a, b with two equivalents of α-haloketones 14a-d led to the production of the corresponding bis(4-arylthiazol)piperazine derivatives 15a-h in good yields. The structures of the synthesized compounds were confirmed from elemental and spectral data (FTIR, MALDI-TOF, (1)H, and (13)C NMR). The cytotoxicity of the new compounds was screened against hepatoblastoma (HepG2), human colorectal carcinoma (HCT 116), breast cancer (MCF-7), and Human Dermal Fibroblasts (HDF). Interestingly, all compounds showed promising cytotoxicity against most of the cell lines. Interestingly, compounds 7b, 9a, and 9i exhibited IC(50) values of 3.5, 12.1, and 1.2 nM, respectively, causing inhibition of 89.7%, 83.7%, and 97.5%, compared to Erlotinib (IC(50) = 1.3 nM, 97.8% inhibition). Compound 9i dramatically induced apoptotic cell death by 4.16-fold and necrosis cell death by 4.79-fold. Compound 9i upregulated the apoptosis-related genes and downregulated the Bcl-2 as an anti-apoptotic gene. Accordingly, the most promising EGFR-targeted chemotherapeutic agent to treat colon cancer was found to be compound 9i.