Novel (E)-1-aryl-2-(3,5-dimethyl-4-(aryldiazenyl)-1H-pyrazol-1-yl)ethanones: solvent-free synthesis and antimicrobial, antioxidant and UV-mediated DNA damage protective activity studies

In search of new biologically active compounds, some novel (E)-1-aryl-2-(3,5-dimethyl-4-(aryldiazenyl)-1H-pyrazol-1-yl)ethanones 3a–u have been synthesized via solvent-free greener approach. All compounds were characterized on the basis of a combined use of IR, NMR (1H, 13C), mass spectrometry and elemental analyses. In order to establish the position of methyl groups in the compound 3b, 2D NMR (COSY, HSQC and HMBC) spectroscopic technique has also been used. To explore the biological potential, compounds were evaluated for their antimicrobial, antioxidant and UV-mediated DNA damage protective activity. Among the series, six compounds 3b, 3i, 3k, 3l, 3m and 3t were found to exhibit a very good level of antibacterial activity and four compounds 3g, 3o, 3p and 3t were emerged as an efficient class of antifungal agents in reference to the standard drugs, viz ciprofloxacin and amphotericin B, respectively. In studying the UV-mediated DNA damage protective activity, all compounds 3a–u (except 3d) protected the plasmid DNA from the UV damaging effect in which 3e was found to be the most potent DNA-protecting agent which avoids the transformation of the native supercoiled form into an open circular and linear form. In addition, the compounds 3f, 3m and 3t were found to be active in antioxidant screening using DPPH assay.