5-methyl-N'-(thiophen-2-ylmethylene)-1H-pyrazole-3-carbohydrazide as potent anticancer agent: Synthesis, spectroscopic characterization, anticancer activity and DFT studies

Abstract

A new pyrazole-hydrazide hydrazone derivative, named 5-methyl-N'-(thiophen-2-ylmethylene)-1H-pyrazole-3-carbohydrazide (TMPC) has been synthesized and characterized by FT-IR, UV–Vis, ¹H NMR, ¹³C NMR, and HRMS-ESI. Its cytotoxic activity was tested on various cancer and healthy cell lines using the XTT method. In addition, the advanced anticancer mechanism was investigated by flow cytometry analysis. Hybrid B3LYP/6–311++G** calculations reveal two stable C1 and C2 conformers of TMPC with energy differences of 28.96 kJ/mol in the gas phase and 8.50 kJ/mol in ethanol solution. Comparisons among the experimental NMR, UV and infrared spectra with the predicted ones support the presence of both forms in solution. The presence of dimer C2 justify the intensities and numerous bands observed in the IR spectrum in the 2000–10 cm⁻¹ region. Probably, the repulsion between the N7 and O1 atoms in C1 explain its lower stability and the higher solvation energy (-108.20 kJ/mol) observed for this form in ethanol than C2 (-88.01 kJ/mol). NBO calculations suggest that both forms are stable in the two media while the AIM analyses evidence the higher stability of C2 than C1 due to the N9-H22···N7 interaction observed only for this conformer in the gas phase. Gap values suggest high reactivities of both forms, as compared with similar pyrazole-carbohydrazide species. Full vibrational assignments are reported for both forms of TMPC together with the main scaled force constants. The XTT results showed that TMPC exhibited a selective cytotoxic effect on the tested cancer cell lines in a dose- and time-dependent manner, and also displayed the most potent cytotoxic activity against breast cancer MCF-7 cells with an IC₅₀ value of 22.79 µM after 48 h Flow cytometric analyses showed that TMPC induced apoptosis and suppressed PI3K/Akt signaling in MCF-7 cells.