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This work describes the synthesis, spectroscopy, time-dependent density-functional theory (TDDFT) studies and electrocatalytic activity towards the CO2 reduction of 4′-substituted terpyridine ligand-coordinated Re(i) complexes.

A pharmacophore model was generated and validated by using known human DNA ligase inhibitors for the identification of a novel series of monocarbonyl curcumin–thiourea/thiazole hybrids as human DNA ligase I (hLigI) inhibitors. These compounds (14–49) were synthesized and their antiligase and cytotoxic activities were evaluated in vitro. Several compounds from this series have shown significant inhibition of purified hLigI activity and exhibited a low micro molar range of cytotoxic activity against one or more cancer cell lines, with IC50 values ranging from 1.3–48.8 μM. Among these, compound 23 showed antiligase activity at an IC50 value 24.9 ± 1.8 μM, and selective cytotoxicity against DLD1 cancer cell line (IC50 value 8.7 ± 1.9 μM) compared to the reference curcumin (IC50 values were 51.9 ± 8.7 μM and 33.2 ± 1.8 μM for antiligase and cytotoxic activities against DLD1 cell line, respectively), and docking studies showed considerable interactions of compound 23 with hLigI. This new class of potent hLigI inhibitors will serve as a potential lead for further optimization and drug development.

A series of new dihydropyrimidinone–semicarbazone hybrids were successfully synthesised by integrating regioselective multicomponent reaction with the pharmacophore hybridization approach. All the synthesised compounds were evaluated for their hLig1 inhibition potency and most of them were found to be good to moderately active. Out of the tested derivatives, compound 6f showed selective anti-proliferative activity against HepG2 cells in a dose-dependent manner with an IC50 value of 10.07 ± 1.2. It also reduced cell survival at ≤20 μM concentration. Further, analysis of treated HepG2 cell lysates by western blot assay showed increased γ-H2AX levels and upregulation of p53, leading to apoptosis. In silico docking results explain the binding modes of compound 6f to the DNA-binding domain of hLig1 enzyme thereby preventing its nick sealing activity. In addition, the favourable pharmacokinetic properties suggest that this new class of hLig1 inhibitors could be promising leads for further drug development.

The processes of DNA replication and repair are accomplished by the concerted action of several proteins. Among them human DNA ligases play an important role during the last step of almost all DNA replication and repair processes, where they seal the nicks between DNA strands. In humans, three kinds of DNA ligases (human DNA ligase I, III, IV) are found. DNA ligase I (hLigI) is involved in both DNA replication as well as in DNA repair pathways and is reported to be over-expressed in rapidly dividing cells, including cancer cells. For this reason, in this study we have targeted hLigI for studying its response as a novel anticancer target. We have screened for ligase I inhibitors from our in-house small molecule library by a previously validated pharmacophore based virtual screening method and found a novel hLigI inhibitor. This compound (S-097/98) demonstrated antiproliferative activities specifically in DLD-1 (colon), MDA-MB-231 (triple negative breast) and HepG2 (liver) cancer cell lines at low micromolar concentrations of 6–7 μM. Mechanistic studies show that the compound can directly interacts with the hLigI protein and inhibits ligation of both the purified protein in vitro, as well as in cell lysate of DLD-1 cells treated with the inhibitor. The compound also arrests cell cycle progression at the G2/M phase and increases the nuclear size of DLD-1 cancer cells, thereby demonstrating its antiproliferative activity. Finally, the compound promotes cellular apoptosis in DLD-1 cells.