Synthesis and biological evaluation of halogenated phenoxychalcones and their corresponding pyrazolines as cytotoxic agents in human breast cancer

Abstract

Novel halogenated phenoxychalcones 2a-f and their corresponding N-acetylpyrazolines 3a-f were synthesised and evaluated for their anticancer activities against breast cancer cell line (MCF-7) and normal breast cell line (MCF-10a), compared with staurosporine. All compounds showed moderate to good cytotoxic activity when compared to control. Compound 2c was the most active, with IC₅₀ = 1.52 µM and selectivity index = 15.24. Also, chalcone 2f showed significant cytotoxic activity with IC₅₀ = 1.87 µM and selectivity index = 11.03. Compound 2c decreased both total mitogen activated protein kinase (p38α MAPK) and phosphorylated enzyme in MCF-7 cells, suggesting its ability to decrease cell proliferation and survival. It also showed the ability to induce ROS in MCF-7 treated cells. Compound 2c exhibited apoptotic behaviour in MCF-7 cells due to cell accumulation in G2/M phase and elevation in late apoptosis 57.78-fold more than control. Docking studies showed that compounds 2c and 2f interact with p38alpha MAPK active sites.

Keywords: Halogenated chalcones; ROS; breast cancer; cell cycle profile; diaryl ether; p38 MAPK; pyrazoline.

Figure 1.

Structures of some reported diaryl ether chalcones I–V and halogenated chalcones II–X with cytotoxic activity.

Figure 2.

Molecular hybridisation of halogenated chalcones and diaryl ether chalcones to yield the designed chalcones 2a–f and N-acetylpyrazoline derivatives 3a–f upon cyclisation.

Scheme 1.

Synthesis of phenoxy halogenated chalcones 2a–f and N-acetylpyrazolines 3a–f. Reagents and conditions: (i) p-Substituted acetophenone, 40% KOH, 95% ethanol, 0 °C, (ii) Hydrazine hydrate, GAA, reflux 3 h.

Figure 3.

ABX spin system on the pyrazoline derivatives 3a–f.

Figure 4.

Structure activity relationship (SAR) of the synthesised chalcones 2a–f and their cyclized derivatives N-acetylpyrazolines 3a–f.

Figure 5.

(A) Graphical representation of the effect of compound 2c on the cell cycle stages of MFC-7 cells. (B) Effect of compound 2c (1.52 µM) on DNA-ploidy flow cytometric analysis of MFC-7 cells after 24 h.

Figure 6.

(A). Percentage and stages of induced apoptosis in control MFC-7 and MFC-7 treated with compound 2c. (B) Representative dot plots of MCF-7 cells treated with 2c (1.52 µM) for 24 h and analysed by flow cytometry after double staining of the cells with Annexin-V-FITC and PI.

Figure 7.

Graphical representation to show the increase of intercellular ROS in 2c treated MCF-7 cells compared to H₂O₂ treated MCF-7 and untreated MCF-7 cells. ROS content was reported as relative fluorescence units (RFU).

Figure 8.

Graphical representation to show that 2c treated MCF-7 cells decreased both total p38 MAPK (p38T) and phosphorylated p38 MAPK (p38P) compared to untreated MCF-7 cells.

Figure 9.

2D interactions of PQA within p38alpha MAP kinase active site.

Figure 10.

3D representation of the superimposition of the co-crystallised (red) and the docking pose (green) of PQA in the active site of p38alpha MAP kinase enzyme.

Figure 11.

(A) 2 D interactions of compound 2c within p38alpha MAP kinase active site; (B) 3 D diagram of compound 2c interactions within p38alpha MAP kinase active site.

Figure 12.

(A) 2 D interactions of compound 2f within p38alpha MAP kinase active site; (B) 3 D diagram of compound 2f interactions within p38alpha MAP kinase active site.