Synthesis, Biological Evaluation And Molecular Docking Studies Of Novel 1-(4,5-dihydro-1H-pyrazol-1-yl)Ethanone-containing 1-methylindol Derivatives As Potential Tubulin Assembling Inhibitors

Microtubules (MTs) are a broadly exploited target for the development of new effective anticancer agents. MTs are highly dynamic polymers mainly composed of a, /β-tubulin heterodimers which turn over continuously. Their polymerization-depolymerization dynamics play a crucial role in various fundamental cellular processes including mitotic spindle formation, organization of intracellular structure, and intracellular transport, as well as cell signaling and secretion. Hence, interfering with MTs function can block cell division and cause cell damage, which is an established strategy to inhibit the proliferation of cancer cells.In the last two decades, an ever increasing number of synthetic indoles which are able to inhibit tubulin polymerization have been reported. The indole nucleus also has been reported to be one of the core nucleuses for potent inhibitors of tubulin polymerization. Furthermore, the addition of methyl to the N atom of indole would be better for the inhibition of tubulin polymerization and cytotoxicity. Also, pyrazolines have gained prominence due to its broad spectrum of biological activities including anticancer, antimicrobial and anti-inflammatory, as well as producing useful intermediates in several organic preparations. It was also reported some pyrazoline derivatives can inhibit tubulin polymerization by binding to the colchicine-site.Therefore, due to these previous researches and molecule modeling studies, we attempt to integrate 1-methylindol with 1-(4,5-dihydro-1H-pyrazol-1-yl)ethanone to screen novel compounds (6a-6v) as potential anti-tubulin agents. A series of novel compounds (6a-6v) containing 1-methylindol and 1-(4,5-dihydro-1H-pyrazol-1-yl)ethanone skeleton were designed, synthesized and biologically evaluated as potential tubulin polymerization inhibitors and anticancer agents. All the synthesized compounds were characterized by 1H NMR,13C-NMR, elemental analysis and ESI-MS. Besides, the crystal structure of compound 60 was determined by X-ray diffraction analysis. The results of biological assay indicated that compound 6q showed the most potent tubulin polymerization inhibitory activity (IC50 = 1.98 μM) and in vitro growth inhibitory activity against A549, MCF-7 and HepG2 cell lines, with IC50 values of 0.15 μM,0.17 μM, and 0.25μM respectively, being comparable to the positive control. Furthermore, compound 6q was a potent inducer of apoptosis in A549 cells and it had typical cellular effects for microtubule interacting agents, causing arrest of the cell cycle in G2/M phase. Confocal microscopy assay and molecular docking results further demonstrated that 6q could bind tightly to the colchicine-site of tubulin and act as an anti-tubulin agent. These studies, along with 3D-QSAR modeling provided an important basis for further optimization of compound 6q as a potential anticancer agent.