Synthesis, biological evaluations and in silico studies on pyrimidine-appended fused pyrazolones as anticancer and antimicrobial agents

A series of twenty-two new pyrimidine appended fused pyrazolones 6a-k and 7a-k has been efficiently synthesized in good yields. Their structural characterization was achieved by physical and spectral analysis data (FTIR, NMR (1H & 13C), 2D NMR and HRMS) and single-crystal X-ray crystallography. All compounds were assayed for their in vitro anticancer activity against three human cancer cell lines viz. (i) human colorectal carcinoma (HCT116), (ii) human breast carcinoma (MCF7), and (iii) human prostate cancer (PC3) employing sulphorhodamine B assay by taking Camptothecin as a standard reference drug, and were also evaluated for their in vitro antimicrobial activities against two Gram-positive bacterial strains viz. E. faecalis (MTCC 439) and S. aureus (NDRI 110), two Gram-negative bacterial strains viz. E. coli (MTCC 723) and S. Typhi (MTCC 3224), and one fungal strain R. oryzae (MTCC 262) employing a quantitative micro-spectrophotometric assay by taking Tetracycline and Fluconazole as standard reference drugs for the antibacterial and antifungal testing, respectively. Amongst all the newly synthesized pyrazolones, 6e and 6j were found to exhibit maximal inhibitory activity against all the tested cancer cell lines, however, these are well active in comparison to the standard drug Camptothecin. The antimicrobial activity evaluation results revealed that compound 6k showed the highest potency against all the bacterial and fungal strains under study in comparison to the respective standard drugs Tetracycline and Fluconazole. Furthermore, in vitro anticancer activity was supported by docking studies performed on the derivatives 6e and 6j with their binding scores -65.842 and -64.555, respectively whereas the binding score of co-crystallized Topotecan was -65.675. Using X-ray crystal structure of compound 6e, DFT analysis gave energies of HOMO and LUMO as -0.2268 a.u.and -0.0872 a.u., respectively while the calculated dipole moment was 9.202833 D. The HOMO is mainly concentrated on chlorophenyl and indenopyrazolone nucleus while LUMO showed larger coefficient on dimethylpyrimidine ring which is in accord with binding interaction results of docking studies.