Synthesis of terphenyl benzimidazoles as tubulin polymerization inhibitors.

A series of new terphenyl benzimidazoles (3a-z and 3aa-ad) were synthesized and evaluated for their anticancer activity. All the 30 compounds have shown moderate to good anticancer potency, however some of the compounds (3j, 3m-t and 3aa-ad) exhibited prominent anticancer potency with GI(50) values ranging from <0.1 to 9.72 µM. These compounds exhibit G2/M phase arrest and the analysis of tubulin by Western blot experiments in case of 3t and 3ad shows the disturbances that are caused in the ratio of soluble versus polymerized tubulin in cells. Compounds 3t and 3ad are the most promising candidates amongst the series and has the potential to be taken up for further detailed studies either alone or in combination with the existing therapies.

3-substituted 2-phenylimidazo[2,1-b]benzothiazoles: synthesis, anticancer activity, and inhibition of tubulin polymerization.

A new series of 3-substituted 2-phenylimidazo[2,1-b]benzothiazoles (3 a-h) were synthesized by C-arylation of 2-arylimidazo[2,1-b]benzothiazoles using palladium acetate as catalyst, and the resulting compounds were evaluated for their anticancer activity. Compounds 3 a, 3 e, and 3 h exhibited good antiproliferative activity, with GI50 values in the range of 0.19-83.1 µM. Compound 3 h showed potent anticancer efficacy against 60 human cancer cell lines, with a mean GI50 value of 0.88 µM. This compound also induced cell-cycle arrest in the G2/M phase and inhibited tubulin polymerization followed by activation of caspase-3 and apoptosis. A high-throughput tubulin polymerization assay showed that the level of inhibition for compound 3 h is similar to that of combretastatin A-4. Molecular modeling studies provided a molecular basis for the favorable binding of compounds 3 a, 3 e, and 3 h to the colchicine binding pocket of tubulin.

Synthesis, anticancer activity and apoptosis inducing ability of bisindole linked pyrrolo[2,1-c][1,4]benzodiazepine conjugates.

A series of bisindole-pyrrolobenzodiazepine conjugates (5a-f) linked through different alkane spacers was prepared and evaluated for their anticancer activity. All compounds exhibited significant anticancer potency and the most potent compounds 5b and 5e were taken up for detailed studies on MCF-7 cell line. Cell cycle effects were examined apart from investigating the inhibition of tubulin polymerization for compounds 2a, 2b, 5b and 5e at 2µM. FACS analysis showed that at higher concentrations (4 and 8µM) there was an increase of sub-G1 phase cells and decrease of G2/M phase cells, thus indicating that compounds 5b and 5e are effective in causing apoptosis in MCF-7 cells. It was also observed that compounds 5b and 5e showed the down regulation of histone deacetylase protein levels such as HDAC1, 2, 3, 8 and increase in the levels of p21, followed by apoptotic cell death. The apoptotic nature of these compounds was further evidenced by increased expression of cleaved-PARP and active caspase-7 in MCF-7 cells.

2-Anilinonicotinyl linked 2-aminobenzothiazoles and [1,2,4]triazolo[1,5-b] [1,2,4]benzothiadiazine conjugates as potential mitochondrial apoptotic inducers.

A series of N-(2-anilino-pyridyl) linked 2-amino benzothiazoles (4a-n) and [1,2,4]triazolo [1,5-b]benzothiadiazine conjugates (5a-j) have been designed, synthesized and evaluated for their antiproliferative activity. Some of these compounds (4h-k, 4n, and 5e) have exhibited potent cytotoxicity specifically against human leukemia HL-60 cell lines with IC(50) values in the range of 0.08-0.70 µM. All these compounds were tested for their effects on the cell cycle perturbations and induction of apoptosis. Morphological evidences of apoptosis, including fragmentation of nuclei and inter nucleosomal DNA laddering formation were clearly observed after 24h exposure to compound 4i. Flow cytometry analysis revealed that compound 4i showed drastic cell cycle perturbations due to concentration dependant increase in the sub-G0 region which comprises of both the apoptotic and debris fraction, thus implying the extent of cell death. These compounds trigger the mitochondrial apoptotic pathway that results in the loss of mitochondrial membrane potential through activation of multiple caspases followed by activation of caspase-3, and finally cleavage of PARP. Further the mechanism of cell death was analysed by fluorescent microscopic analysis and also by scanning electron microscopy. The cytotoxicity of 4i correlated with induction of apoptosis, caspases activation and DNA damage and thus indicating the apoptotic pathway of anticancer effect of these compounds.

Synthesis of aryl-substituted naphthalene-linked pyrrolobenzodiazepine conjugates as potential anticancer agents with apoptosis-inducing ability.

A library of new aryl-substituted naphthalene C8-linked pyrrolo[2,1-c][1,4]benzodiazepine (PBD) conjugates with various linker architectures were designed, synthesized, and evaluated for their anticancer activity against a panel of 11 human cancer cell lines. All 32 conjugates show anticancer potential, with some of them exhibiting particularly high activity (0.01-0.19 µM). Thermal denaturation studies showed effective DNA binding capacity relative to DC-81. In assays for biological activity relating to cell-cycle distribution, these PBD conjugates induce G0/G1-phase arrest and also cause an increase in the levels of p53 and caspase-9 proteins, followed by apoptotic cell death. One conjugate in particular is the most promising candidate of the series, with the potential to be selected for further studies, either alone or in combination with existing anticancer therapies.

Synthesis and biological evaluation of estradiol linked pyrrolo[2,1-c][1,4]benzodiazepine (PBD) conjugates as potential anticancer agents.

A series of new estradiol linked pyrrolo[2,1-c][1,4]benzodiazepine (E(2)-PBD) conjugates (3a-f, 4a-f and 5a-f) with different linker architectures including a triazole moiety have been designed and synthesized. All the 18 compounds have been evaluated for their anticancer activity and it is observed that some of the compounds particularly 4c-e and 5c,d exhibited significant anticancer activity. The detailed biological aspects relating to the cell cycle effects and tubulin depolymerization activity have been examined with a view to understand the mechanism of action of these conjugates. Among all these conjugates, one of the compound 5c could be considered as the most effective compound particularly against MCF-7 breast cancer cell line.

Synthesis and anticancer activities of new Benzothiadiazinyl Hydrazinecarboxamides and Anilino[1,2,4]triazolo[1,5-b][1,2,4]thiadiazine 5,5-diones.

Two series of compounds (5-14 and 15-23) based on the scaffolds of 2-(1,1-dioxido-4-phenyl-4Hbenzo[e][1,2,4]thiadiazin-3-yl)-N-(4-methoxyphenyl)hydrazinecarboxamide (5) and 2-((4-methoxyphenyl)amino)-10-phenyl-10H-benzo[e][1,2,4]triazolo[1,5-b][1,2,4]thiadiazine 5,5-dioxide (15) respectively, were designed and synthesized. These compounds were tested for anticancer activity against various cancer cell lines including lung, ovary, prostate, breast and colon cancers. They exhibited moderate to good inhibitory activity against the above cell lines and compound 9 was found to be the most active one from these two series. Further studies showed that cancer cell growth inhibition by compounds 22 and 23 could be in part due to the inhibition of tubulin polymerization, with the IC50 values of 4.70 and 5.25 µM, respectively.

Synthesis of 3,3-diindolyl oxyindoles efficiently catalysed by FeCl3 and their in vitro evaluation for anticancer activity.

A simple and highly efficient method has been developed for the synthesis of 3,3-diindolyl oxyindoles by the reaction of indoles with isatin or 5-fluoro isatin using a catalytic amount (5 mol%) of FeCl(3) at room temperature in a short reaction time in high yields. All these compounds were evaluated against a panel of five human cancer lines and most of them showed potent cytotoxicity. Compound 4b showed IC(50) of 4.7 and 5 microM against SK-N-SH and DU-145 cell lines, respectively, whereas 4c, 4d, 4f and 4k showed IC(50) of 2.2, 1.2, 3.6 and 3.6 microM, respectively, against DU-145 cell line. Interestingly, some of the compounds are selectively potent in prostate cancer (DU-145) with IC(50) values of 1.2-19.6 microM.

An efficient synthesis of bis(indolyl)methanes and evaluation of their antimicrobial activities.

A versatile and efficient method has been developed for the synthesis of bis(indolyl)methanes by using aluminium triflate (0.5 mol%) as a novel catalyst. Further, some of the synthesized compounds were evaluated for their efficacy as antibacterial and antifungal activities. Most of the compounds have shown moderate to good inhibitory activity.

Synthesis, DNA-binding ability and evaluation of antitumour activity of triazolo[1,2,4]benzothiadiazine linked pyrrolo[2,1-c][1,4]benzodiazepine conjugates.

A series of triazolobenzothiadiazine-pyrrolobenzodiazepine conjugates linked through different alkane spacers have been prepared. These compounds have exhibited significant cytotoxicity against most of the cell lines examined. Compound 5a displays GI(50) values from 1.83 to 2.38 microM against seven human tumour cell lines, and is identified as a promising lead compound from this series. Their DNA thermal denaturation studies have also been carried out, and one of the compounds 5c elevates the DNA helix melting temperature of the CT-DNA by 2.6 degrees C after incubation for 36 h.

Synthesis, structural characterization and biological evaluation of novel [1,2,4]triazolo [1,5-b][1,2,4]benzothiadiazine-benzothiazole conjugates as potential anticancer agents.

Two series of 10-substituted 5,5-dioxo-5,10-dihydro[1,2,4]triazolo[1,5-b][1,2,4]benzothiadiazine 2-methyl/ethyl sulfanyl benzothiazole derivatives (5a-d) and 10-substituted 5,5-dioxo-5,10-dihydro[1,2,4]triazolo[1,5-b][1,2,4] benzothiadiazine 2-phenoxy benzothiazole derivatives (16a-c) were synthesized and their structures confirmed by NMR, MS, IR and X-ray crystallography. These compounds were evaluated for their cytotoxicity against 60 human tumour cell lines. One of the synthesized compounds (5b) exhibited significant inhibitory activity against most of the cell lines and has been further evaluated for the five-dose screening.