Nataša Perin

Novel biologically active nitro and amino substituted benzimidazo[1,2-a]quinolines.

This manuscript described the synthesis and biological activity of novel nitro substituted E-2-styryl-benzimidazoles and E-2-(2-benzimidazolyl)-3-phenylacrylonitriles and nitro and amino substituted benzimidazo[1,2-a]quinolines (4-5, 6-11, 17-20, and 21-32). All of the compounds showed significant growth inhibitory effect towards five tumor cell lines, whereby the IC(50) concentrations of 11, 20, 28, 29, 30, 32 are in the low micromolar range (IC(50)=2-19 μM). The DNA binding experiments did not show significant affinity of two selected compounds towards ct-DNA. The flow cytometry analysis of potential cell cycle perturbations after the treatment with compounds 9, 11, 25, and 29 demonstrated that all of the compounds (5 μM ≈ IC(50)) significantly delayed the progression through G1 phase, as demonstrated by the accumulation of cells in G1 phase, accompanied with the reduction of the cell number in the cells in S phase, which does not point to DNA damage as the main mechanism of action. Also, fluorescence microscopy study showed cytoplasmic distribution of the compounds, demonstrating that DNA is not the primary target of compounds. Thus, considerable antiproliferative effects of studied compounds are due to interactions with other biological targets within cells.

Biological activity and DNA binding studies of 2-substituted benzimidazo[1,2-a]quinolines bearing different amino side chains

This manuscript describes the synthesis and biological activity of 2-substituted benzimidazo[1,2-a]quinolines substituted with different amino side chains on the quinoline nucleus prepared by microwave assisted amination. The majority of compounds were newly synthesized and active at submicromolar IC50 concentrations, while the alkylamino substituents, either acyclic or cyclic, increased antitumor activities in comparison with previously published nitro and amino substituted benzimidazo[1,2-a]quinolines. The compound with the longest tertiary amino side chain (16) was the least active. A series of additional experiments, including DNA binding propensities, topoisomerases I and II inhibition, inhibition of recombinant green fluorescent protein in a cell-free translation system, cell cycle perturbances and cellular localization, was performed to shed more light on the mechanisms of action of the most active compounds. The DNA intercalation activity correlates with anti-proliferative effect. Several DNA intercalators (11, 20 and 21) also evidence some sequence selective DNA binding. However, only N,N-dimethylaminopropyl analogue 11 was unequivocally demonstrated to be a strong DNA-binder and intercalative agent, which efficiently targets DNA in the cells, while the activity of compound 10, with a bulky i-butylamino side chain, points to its potential antimitotic activity.

Fluorescent benzimidazo[1,2-a]quinolines: synthesis, spectroscopic and computational studies of protonation equilibria and metal ion sensitivity

We describe the UV-Vis and fluorescence spectroscopic characterization of newly synthesised amino and diamino substituted benzimidazo[1,2-a]quinolines and their various 1 : 1 metal complexes together with the related computational analysis of their acid/base properties and metal binding affinities. The work was performed in order to evaluate the photophysical features of these compounds and assess their potential chemosensor activity towards pH and metal ions in several polar and non-polar organic solvents. In addition, pH titrations and titration with metal chloride salts were carried out to determine the selectivity towards Co2+, Cu2+, Ni2+ and Zn2+ cations and explore their potential as chemosensors and pH probes. While all systems exhibit notable but impractical differences in sensitivities and spectral responses with the used metals, computational analysis aided in identifying benzimidazo[1,2-a]quinolines mono- and disubstituted with the piperazine fragment as very promising and efficient pH sensors in the acidic environment, particularly in the range of pH ≈ 3, which is extended to pH ≈ 6 upon the addition of metal cations. Their analytical features are significantly better than those involving the chain amino substituents, and their further development is strongly suggested.

Synthesis and Antiproliferative Activity of Novel 2-Substituted N-Methylated Benzimidazoles and Tetracyclic Benzimidazo [1,2-a]Quinolines

ABSTRACT In this paper, the synthesis, antiproliferative activity in vitro and structure–activity relationship of N-methylated 2-benzimidazoles related to 2,3-acrylonitriles and benzimidazo [1,2-a]quinolines bearing halogeno or amino substituent is described. Amino-substituted N-methylated benzimidazo[1,2-a]quinolines were prepared by using microwave-assisted amination from corresponding halogeno-substituted precursors. All newly prepared compounds were tested against tree human cancer cells to assess their antiproliferative activity in vitro. Compounds 4a and 4b display certain selective activity against MCF-7 cells together with the N,N-dimethylamino-substituted derivative 4e with IC50 0.4 µM. Cyclic derivatives 7a, 7b, and 8 were more active with IC50 in micromolar range of concentrations but without any selectivity among tested cells. Among the most active compounds, 2-amino-substituted derivatives 9a and 9b were also selective against HCT116 cells with IC50 values 0.2 µM and 0.4 µM, respectively. The influence of compounds 9a and 9b on the cell cycle of HCT 116 revealed that both compounds induced a strong reduction of the percentage of cells in S phase, along with the induction of cell death.

Different positions of amide side chains on the benzimidazo[1,2-a]quinoline skeleton strongly influence biological activity

Benzimidazo[1,2-a]quinolines substituted with amide chains have been evaluated for their antiproliferative, antibacterial and antiviral activity in vitro. Amido-substituted cyclic derivatives were synthesized by classical organic synthetic reactions in order to study the influence of the type and length of the amide side chain as well as its position on the tetracyclic skeleton on biological activity. The most promising antiproliferative activity (i.e. sub-micromolar IC50 concentrations) was displayed by 6-N,N-dimethylaminopropyl 21, 6-N,N-diethylaminoethyl 22 and the 2- and 6-N,N-dimethylaminopropyl substituted derivative 25. Additionally, micromolar concentrations of compounds 21 and 25 induced apoptosis in human cervical carcinoma HeLa cells. Compounds 28, 29 and 30, substituted with the isobutyl, N,N-dimethylaminopropyl and N,N-diethylaminoethyl amide side chain placed at position 2, displayed antiviral activity against herpes simplex virus (HCV) (EC50 1.8–6.8 μM) and human coronavirus (EC50 4–12 μM). Furthermore, N,N-dimethylaminopropyl 21 and N,N-diethylaminoethyl 22 substituted compounds bearing the amide side chain at position 6 of the tetracyclic skeleton were active against S. epidermidis and C. albicans strains.

Amino-Substituted Benzamide Derivatives as Promising Antioxidant Agents: A Combined Experimental and Computational Study

We prepared a range of N-arylbenzamides with a variable number of methoxy and hydroxy groups, bearing either amino or amino-protonated moieties, and used DPPH and FRAP assays to evaluate their antioxidant capacity. Most of the systems exhibit improved antioxidative properties relative to the reference BHT molecule in both assays. Combining results from both sets of experiments, the most promising antioxidative potential was displayed by the trihydroxy derivative 26, which we propose as a lead compound for a further optimization of the benzamide scaffold. Computational analysis helped in interpreting the observed trends and demonstrated that protonated systems are better antioxidants than their neutral counterparts, while underlying the positive influence of the electron-donating methoxy group on the antioxidant properties, thus confirming the experiments. It also revealed that the introduction of the hydroxy groups shifts the reactivity from both amide and amine groups toward this moiety and additionally enhances antioxidative features. This is particularly evident in 26H•+, which owes its pronounced reactivity to the stabilizing [O•···H-O] hydrogen bonding between the created phenoxyl radical and the two neighboring hydroxy groups. We demonstrated that its antioxidative activities are more favorable than those for analogous trihydroxy derivatives without the N-phenyl group or without the amide moiety, which strongly justifies the employed strategy in utilizing bisphenylamides in designing potent antioxidants.

Synthesis and antiproliferative activity of amino substituted benzimidazo[1, 2-a]quinolines as mesylate salts designed by 3D-QSAR analysis

An experimental search for new benzimidazole derivatives with enhanced antiproliferative activity was successfully guided by QSAR modelling. Robust 3D-QSAR models were derived on an available database of compounds with previously measured activities. Our QSAR analysis revealed that an increase of the antiproliferative activities towards H460, HCT 116, MCF-7 and SW 620 cells will be obtained if new compounds are charged at a pH range from 5 to 7 and if their hydrophobicity is increased compared to the dataset compounds. Novel benzimidazo[1,2-a]quinolines bearing quarternary amino groups with corresponding aliphatic chains were designed, and their antiproliferative activities were computationally predicted. Using uncatalysed microwave-assisted amination reactions, 14 novel compounds were obtained to assess their antiproliferative activities towards H460, HCT 116, MCF-7, and SW 620 tumour cell lines in vitro. Novel compounds showed antiproliferative activities at micromolar and submicromolar inhibition concentrations. Experimental measurements of antiproliferative activities validation the QSAR models showing very good agreement between experimentally measured activities and computational predictions. In an attempt to elucidate the mode of action through which benzimidazole derivatives accomplish their antiproliferative activities, thermal denaturation experiments were performed to test their DNA-binding properties.Graphical Abstract

Synthesis and SAR Study of Novel Amidino 2-substituted Benzimidazoles as Potential Antibacterial Agents

A series of novel 2-substituted benzimidazole derivatives were synthesized and their antibacterial activity was assessed against selected Gram-positive and Gram-negative bacteria. The specific moiety at the 2-position of the benzimidazole was extensively modified with several fused heterocyclic functional groups containing nitrogen and sulfur heteroatoms. In addition, the influence of different amidino groups at the position 5 of benzimidazole scaffold was evaluated. The values of clogP (a partition coefficient) and clogD7.5 (calculated distribution coefficient, pH 7.5) were determined and the lipophilic character of compounds has been found to be important parameter for the observed activity of the tested benzimidazole derivatives against Moraxella catarrhalis. The indolo 2-substituted benzimidazole 13a demonstrated solid activity against Staphylococcus aureus (MICs 16 μg/mL) and Moraxella catarralis (MICs 2 μg/mL) and represents promising lead molecule for further optimization.