Discovery of certain benzyl/phenethyl thiazolidinone-indole hybrids as potential anti-proliferative agents: Synthesis, molecular modeling and tubulin polymerization inhibition study.

A series of certain benzyl/phenethyl thiazolidinone-indole hybrids were synthesized for the study of anti-proliferative activity against A549, NCI-H460 (lung cancer), MDA-MB-231 (breast cancer), HCT-29 and HCT-15 (colon cancer) cell lines by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). We found that compound G37 displayed highest cytotoxicity with IC50 value of 0.92 ±â€¯0.12 µM towards HCT-15 cancer cell line among all the synthesized compounds. Moreover, compound G37 was also tested on normal human lung epithelial cells (L132) and was found to be safe in contrast to HCT-15 cells. The lead compound G37 showed significant G2/M phase arrest in HCT-15 cells. Additionally, compound G37 significantly inhibited tubulin polymerization with IC50 value of 2.92 ±â€¯0.23 µM. Mechanistic studies such as acridine orange/ethidium bromide (AO/EB) dual staining, DAPI nuclear staining, annexinV/propidium iodide dual staining, clonogenic growth inhibition assays inferred that compound G37 induced apoptotic cell death in HCT-15 cells. Moreover, loss of mitochondrial membrane potential with elevated intracellular ROS levels was observed by compound G37. These compounds bind at the active pocket of the α/ß-tubulin with higher number of stable hydrogen bonds, hydrophobic and arene-cation interactions confirmed by molecular modeling studies.

New (3-(1H-benzo[d]imidazol-2-yl))/(3-(3H-imidazo[4,5-b]pyridin-2-yl))-(1H-indol-5-yl)(3,4,5-trimethoxyphenyl)methanone conjugates as tubulin polymerization inhibitors.

A series of new (3-(1H-benzo[d]imidazol-2-yl))/(3-(3H-imidazo[4,5-b]pyridin-2-yl))-(1H-indol-5-yl)(3,4,5-trimethoxyphenyl)methanone conjugates 4-6(a-i) were synthesized and evaluated for their antiproliferative activity on selected human cancer cell lines such as prostate (DU-145), lung (A549), cervical (HeLa) and breast (MCF-7). Most of these conjugates showed considerable cytotoxicity with IC50 values ranging from 0.54 to 31.86 µM. Among them, compounds 5g and 6f showed significant activity against human prostate cancer cell line DU-145 with IC50 values of 0.68 µM and 0.54 µM, respectively. Tubulin polymerization assay and immunofluorescence analysis results suggest that these compounds effectively inhibit microtubule assembly formation in DU-145. Further, the apoptosis-inducing ability of these derivatives (5g and 6f) was confirmed by Hoechst staining, measurement of mitochondrial membrane potential and ROS generation and annexin V-FITC assays.

Telomerase Inhibition and Human Telomeric G-Quadruplex DNA Stabilization by a ß-Carboline-Benzimidazole Derivative at Low Concentrations.

Guanine rich regions in DNA, which can form highly stable secondary structures, namely, G-quadruplex or G4 DNA structures, affect DNA replication and transcription. Molecules that stabilize G4 DNA have become important in recent years. In this study, G4 DNA stabilization, inhibition of telomerase, and anticancer activity of synthetic ß-carboline-benzimidazole derivatives (5a, 5d, 5h, and 5r) were studied. Among them, derivatives containing a 4-methoxyphenyl ring at C1 and a 6-methoxy-substituted benzimidazole at C3 (5a) were found to stabilize telomeric G-quadruplex DNA efficiently. The stoichiometry and interaction of a synthetic, ß-carboline-benzimidazole derivative, namely, 3-(6-methoxy-1H-benzo[d]imidazol-2-yl)-1-(4-methoxyphenyl)-9H-pyrido[3,4-b]indole (5a), with human intermolecular G-quadruplex DNA at low concentrations were examined using electrospray ionization mass spectrometry. Spectroscopy techniques indicate that 5a may intercalate between the two stacks of G-quadruplex DNA. This model is supported by docking studies. When cancer cells are treated with 5a, the cell cycle arrest occurs at the sub-G1 phase. In addition, an apoptosis assay and fluorescence microscopy studies using cancer cells indicate that 5a can induce apoptosis. Results of biochemical assays such as the polymerase chain reaction stop assay and telomerase activity assay indicate that 5a has the potential to stabilize G-quadruplex DNA, and thereby, it may interfere with in vitro DNA synthesis and decrease telomerase activity. The results of this study reveal that the ß-carboline-benzimidazole derivative (5a) is efficient in G-quadruplex DNA stabilization over double-stranded DNA, inhibits telomerase activity, and induces apoptosis in cancer cells.

Synthesis of thiazole linked indolyl-3-glyoxylamide derivatives as tubulin polymerization inhibitors.

A series of thiazole linked indolyl-3-glyoxylamide derivatives were synthesized and evaluated for their in vitro cytotoxic activity against DU145 (prostate), PC-3 (prostate), A549 (lung) and HCT-15 (colon) cancer cell lines by employing the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Among all the synthesized compounds, compound 13d displayed cytotoxicity of IC50 = 93 nM towards DU145 cancer cell line. The most active compound 13d was also tested on RWPE-1 cells and was found to be safe compared to the DU145 cells. The target compounds were also evaluated for their inhibition activity of tubulin polymerization. Further, the treatment of compound 13d on DU145 cells led to the inhibition of cell migration ability. The detailed studies such as acridine orange/ethidium Bromide (AO/EB), DAPI, annexin V-FITC/propidium iodide staining assay suggested that the compound 13d induced apoptosis in DU145 cells. The influence of the cytotoxic compound 13d on the cell cycle distribution was assessed on the DU145 cell line, exhibiting a cell cycle arrest at the G2/M phase. Moreover, the treatment with compound 13d caused collapse of mitochondrial membrane potential and elevated intracellular ROS levels in DU145 cells. The results from molecular modelling studies revealed that these compounds bind at the colchicine binding site of the tubulin. Thus, this new molecular scaffold could be a new lead for the development of anticancer agents that target tubulin.

Synthesis of C5-tethered indolyl-3-glyoxylamide derivatives as tubulin polymerization inhibitors.

A series of C5-tethered Indolyl-3-glyoxylamide derivatives were synthesized and evaluated for their in vitro cytotoxic activity against DU145 (prostate), PC-3 (prostate), A549 (lung) and HCT-15 (colon) cancer cell lines by employing the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Among all the synthesized compounds, compound 7f displayed cytotoxicity of IC50 = 140 nM towards DU145 cancer cell line. The treatment of DU145 cells with 7f led to inhibition of cell migration ability. Futher, the detailed studies such as acridine orange/ethidium Bromide (AO/EB), DAPI, annexin V-FITC/propidium iodide staining assay suggested that the compound 7f induced apoptosis in DU145 cells. The influence of the cytotoxic compound 7f on the cell cycle distribution was assessed on the DU145 cell line, exhibiting a cell cycle arrest at the G2/M phase (hallmark of tubulin polymerization) and next inhibited tubulin polymerization with IC50 0.40 µM. Furthermore, the treatment with compound 7f caused collapse of mitochondrial membrane potential and elevated intracellular superoxide ROS levels in DU145 cells. Western blotting was performed to examine the levels of apoptotic proteins (Bcl-2 and Bax); the study confirmed that compound 7f induced apoptosis through apoptosis-related protein expression. Thus, these studies provided a new molecular scaffold for the further development of anticancer agents that target tubulin.

Synthesis and apoptosis inducing studies of triazole linked 3-benzylidene isatin derivatives.

In our venture towards the development of effective cytotoxic agents, a panel of triazole linked 3-benzylidene isatin hybrids were synthesized and characterized by IR, 1H NMR, 13C NMR and Mass spectral analysis. All the newly synthesized target compounds were assessed against DU145 (prostate), PC-3 (prostate), MDA-MB-231 (breast), BT549 (breast), A549 (lung) and HeLa (cervical) human cancer cell lines by employing MTT assay for their cytotoxic potential. Significantly, compound Z-8l was found to be most potent amongst all the tested compounds with an IC50 value of (3.7 ± 0.05 µM) on DU145 cells. The most active compound (Z-8l) was also tested on RWPE-1 (normal prostate) cells and was found to be safe compared to the DU145 cells. The influence of the cytotoxic compound Z-8l on the cell cycle distribution was assessed on the DU145 cell line, exhibiting a cell cycle arrest at the G2/M phase. Additionally, treatment with compound Z-8l caused collapse of mitochondrial membrane potential (DΨm) in DU145 cells. Moreover, acridine orange/ethidium bromide staining, DAPI nuclear staining, DCFDA staining and annexin V binding assay confirmed that compound Z-8l can induce cell apoptosis in DU145 cells. Western blotting was performed to examine the appearance of active forms of cytochrome c, Bax, Bcl2 and PARP (Poly ADP ribose polymerase), indicator proteins of apoptosis in DU145 cells; the study confirmed the triggering of mitochondrial mediated apoptotic pathway upon exposure of compound Z-8l.

Synthesis and biological evaluation of oxindole linked indolyl-pyrimidine derivatives as potential cytotoxic agents.

In our endeavor towards the development of effective cytotoxic agents, a series of oxindole linked indolyl-pyrimidine derivatives were synthesized and characterized by IR, (1)H NMR, (13)C NMR and Mass spectral analysis. All the newly synthesized target compounds were assessed against PA-1 (ovarian), U-87MG (glioblastoma), LnCaP (prostate), and MCF-7 (Breast) cancer cell lines for their cytotoxic potential, with majority of them showing inhibitory activity at low micro-molar concentrations. Significantly, compound 8e was found to be most potent amongst all the tested compounds with an IC50 value of (2.43±0.29µM) on PA-1 cells. The influence of the most active cytotoxic compound 8e on the cell cycle distribution was assessed on the PA-1 cell line, exhibiting a cell cycle arrest at the G2/M phase. Moreover, acridine orange/ethidium bromide staining and annexin V binding assay confirmed that compound 8e can induce cell apoptosis in PA-1 cells. These preliminary results persuade further investigation on the synthesized compounds aiming to the development of potential cytotoxic agents.

Aldehyde-Promoted One-Pot Regiospecific Synthesis of Acrylamides Using an in Situ Generated Molybdenum Tetracarbonyl Amine [Mo(CO)4(amine)2] Complex.

A novel complex system generated in situ from Mo(CO)6 and an amine is described for the regiospecific aminocarbonylation of various terminal alkynes. The Mo(CO)6-amine system played a dual role as complexing agent and as CO donor, thus making this process palladium-free.