Marijana Hranjec

Novel Amidino-Substituted Thienyl-and Furylvinylbenzimidazole : Derivatives and Their Photochemical Conversion into Corresponding Diazacyclopenta[c]fluorenes. Synthesis, Interactions with DNA and RNA, and Antitumor Evaluation. 4

Synthesis of novel nonfused amidino-substituted thienyl- and furylvinylbenzimidazole: derivatives and their photochemical cyclization into corresponding diazacyclopenta[ c]fluorenes is described. All studied compounds showed prominent growth inhibitory effect. The fused compounds showed stronger activity than nonfused ones, whereby imidazolyl-substituted compound 11 proved to be the most active one. Besides, it induced strong G2/M arrest of the cell cycle followed by drastic apoptosis, which is in accordance with the DNA intercalative binding mode determined by the spectroscopic studies. Nonfused derivatives induced strong S phase arrest of the cell cycle followed by apoptosis that together with DNA minor groove binding mode pointed to topoisomerase I inhibition. In addition, all nonfused compounds revealed pronounced selectivity toward tumor cells in comparison with nontumor cells. On the basis of the presented results, both nonfused and fused thiophene-containing imidazolyl derivatives should be considered as promising lead compounds for further investigation.

Benzimidazole derivatives related to 2,3-acrylonitriles, benzimidazo[1,2-a]quinolines and fluorenes: Synthesis, antitumor evaluation in vitro and crystal structure determination

A synthesis and biological evaluation of new benzimidazole derivatives, related to 2,3-disubstituted acrylonitriles, benzimidazo[1,2-a]quinoline-6-carbonitriles and heteroaromatic fluorenes was described. The molecular and crystal structures of three compounds 4, 16 and 17 reveal that non-fused fluoro derivative, 4, deviates from planarity by 13.11(2) degrees, while fused methyl, 16, and fluoro, 17, derivatives are planar within 4 degrees exhibiting a planar aromatic surface capable to intercalate into double-stranded DNA. Compound 4 exists as E-isomer. The crystal structures confirmed that hydrogen bonding patterns are characterized dominantly by the weak C-H...N(F) bonds, except in the case of 4 where the presence of ethanol molecule of crystallization resulted in the N-H...O and O-H...N hydrogen bonds formation. In the crystal structures of 16 and 17 cyano group participates in hydrogen bonding formation, while in 4 this is not the case. All compounds, except 16 and 14 exerted pronounced antiproliferative activity on five tumor cell lines, whereby 2-benzimidazolyl-3-N-methylpyrolyl-acrylonitrile 13 and its fused analogue 23 exerted the highest activity on all cell lines (IC50=0.8-30 microM) and showed a special selectivity toward HeLa cells. There is no major difference in the biological activity between non-fused and fused analogues. Similarly, all compounds showed significant interaction with ct-DNA, supporting the fact that their antitumor activity could partially be the consequence of DNA-binding. The cyano moiety is important for the activity, but not the selectivity of tested compounds.

Synthesis, spectroscopic characterization and antiproliferative evaluation in vitro of novel Schiff bases related to benzimidazoles.

A series of novel benzimidazole substituted Schiff bases were synthesized by reaction of aromatic aldehydes with corresponding 2-aminobenzimidazoles. Their structure has been studied by 1H and 13C NMR, IR and UV/Vis spectroscopy. Majority of prepared Schiff bases were tested on their antiproliferative activity in vitro and exerted non-specific antiproliferative activity on the tested cell lines at the highest tested concentration. Compounds 18 and 19 exerted the strongest non-specific antiproliferative effect on all cell lines and a concentration-dependent effect on HeLa and MCF-7 cell lines at micromolar concentrations but simultaneously being highly cytotoxic on human fibroblasts as well.

Differential antiproliferative mechanisms of novel derivative of benzimidazo[1,2-α]quinoline in colon cancer cells depending on their p53 status

In the present article, we describe a mechanistic study of a novel derivative of N-amidino-substituted benzimidazo[1,2-α]quinoline in two human colorectal cancer cell lines differing in p53 gene status. We used a proteomic approach based on two-dimensional gel electrophoresis coupled with mass spectrometry to complement the results obtained by common molecular biology methods for analyzing cell proliferation, cell cycle, and apoptosis. Tested quinoline derivative inhibited colon cancer cell growth, whereby p53 gene status seemed to be critical for its differential response patterns. DNA damage and oxidative stress are likely to be the common triggers of molecular events underlying its antiproliferative effects. In HCT 116 (wild-type p53), this compound induced a p53-dependent response resulting in accumulation of the G1- and S-phase cells and induction of apoptosis via both caspase-3-dependent and caspase-independent pathways. Quinoline derivative triggered transient, p53-independent G2-M arrest in mutant p53 cells (SW620) and succeeding mitotic transition, whereby these cells underwent cell death probably due to aberrant mitosis (mitotic catastrophe). Proteomic approach used in this study proved to be a valuable tool for investigating cancer cell response to newly synthesized compound, as it specifically unraveled some molecular changes that would not have been otherwise detected (e.g., up-regulation of the p53-dependent chemotherapeutic response marker maspin in HCT 116 and impairment in ribosome biogenesis in SW620). Finally, antiproliferative effects of tested quinoline derivative on SW620 cells strongly support its possible role as an antimetastatic agent and encourage further in vivo studies on the chemotherapeutic potential of this compound against colorectal carcinoma. [Mol Cancer Ther 2008;7(7):2121–32]

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.

Novel imidazo[4,5-b]pyridine and triaza-benzo[c]fluorene derivatives: Synthesis, antiproliferative activity and DNA binding studies

In the present paper, we have described the synthesis and biological activity of the novel derivatives of imidazo[4,5-b]pyridines and triaza-benzo[c]fluorenes (7-21, 24-26, 28-29). A preponderance of these compounds exerted strong cytostatic effects on the panel of seven human tumour cell lines in a dose-dependent manner. In particular, imidazo[4,5-b]pyridines and triaza-benzo[c]fluorenes including 2-imidazolinyl derivatives showed the most potent antitumour activity. Similarly, triaza-benzo[c]fluorenes 18 and 20 induced strong growth inhibition of tested tumour cell lines, and showed low cytotoxicity in normal human fibroblasts. DNA interaction studies of these compounds demonstrated that N-methylated 16 and 2-imidazolinyl 28 triaza-benzo[c]fluorenes bind to DNA in an intercalative mode.

Synthesis and antitumor evaluation of some new substituted amidino-benzimidazolyl-furyl-phenyl-acrylates and naphtho[2,1-b]furan-carboxylates.

The multistep synthesis of a series of substituted amidino-benzimidazolyl-furyl-phenyl-acrylic acids esters and substituted amidino-benzimidazolyl-naphtho[2,1-b]furan-carboxylic acids esters is described starting from corresponding 3-(2-furyl)-2-phenyl-acrylic acids. The new compounds were tested on the cytostatic activities against malignant cell lines: pancreatic carcinoma (MiaPaCa2), breast carcinoma (MCF7), cervical carcinoma (HeLa), laryngeal carcinoma (Hep2), colon carcinoma (HT 29), melanoma (HBL), and human fibroblasts cell line (WI38). All compounds inhibited the proliferation of tumor cell lines. Inhibitory effect of examined compounds depended on concentration, but without significant difference among the type of tumor cells. The compounds 2 and 5 exerted very low inhibitory effect on the growth of human fibroblasts. Unsubstituted derivative 8 has not inhibited any tested cell lines.

Synthesis of Novel Benzimidazolyl-substituted Acrylonitriles and Amidino-substituted Benzimidazo[1,2-a]Quinolines

A series of novel benzimidazole derivatives 3-10 were synthesized. Benzimidazolyl-substituted acrylonitriles 3 and 4 underwent a photochemical dehydrocyclization reaction to give the corresponding mono- and dicyano-substituted benzimidazo[1,2-a] quinolines 5 and 6. Pinner reaction of these compounds did not give the expected mono- and diamidines, but rather only compounds 7-10, with amido groups at 6-position were isolated. A mechanism for the reaction is proposed. Acyclic compounds 3 and 4, as well as cyclic benzimidazo[1,2-a]quinolines 5-8, exhibit interesting spectroscopic properties and are potential biologically active compounds.

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.