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A new class of pyrazole and isoxazole conjugates were synthesized and evaluated for their cytotoxic activity against various human cancer cell lines. These compounds have shown significant cytotoxicity with lower IC50 values. FACS results revealed that A549 cells treated with these compounds arrested cells at the G2/M phase of the cell cycle apart from activating cyclin B1 protein levels. Particularly, compounds 9a and 9b demonstrated a remarkable inhibitory effect on tubulin polymerization and showed a pronounced inhibitory effect on tubulin polymerization with IC50 values of 1.28 µM and 0.28 µM respectively, whereas nocodazole, a positive control, has shown lower antitubulin activity with an IC50 value of 2.64 µM. Furthermore, these compounds induced apoptosis by loss of mitochondrial membrane potential, propidium iodide (PI) staining and the activation of caspase-3. Results of a fluorescence based competitive colchicine binding assay suggest that these conjugates bind successfully at the colchicine binding site of tubulin. These investigations reveal that such conjugates containing pyrazole with a trimethoxy phenyl ring and indole moieties have potential for the development of newer chemotherapeutic agents.
A series of β-carboline–benzimidazole conjugates bearing a substituted benzimidazole and an aryl ring at C3 and C1 respectively were designed and synthesized. The key step of their preparation was determined to involve condensation of substituted o-phenylenediamines with 1-(substituted phenyl)-9H-pyrido- [3,4-b]indole-3-carbaldehyde using La(NO3)3·6H2O as a catalyst and their cytotoxic potential was evaluated. Conjugates 5a, 5d, 5h and 5r showed enhanced cytotoxic activity (GI50 values range from 0.3 to 7.1 μM in most of the human cancer cell lines) in comparison to some of the previously reported β-carboline derivatives. To substantiate the cytotoxic activity and to understand the nature of interaction of these conjugates with DNA, spectroscopy, DNA photocleavage and DNA topoisomerase I inhibition (topo- I) studies were performed. These conjugates (5a, 5d and 5r) effectively cleave pBR322 plasmid DNA in the presence of UV light. In addition, the effect of these conjugates on DNA Topo I inhibition was studied. The mode of binding of these new conjugates with DNA was also examined by using both biophysical as well as molecular docking studies, which supported their multiple modes of interaction with DNA. Moreover, an in silico study of these β-carboline–benzimidazole conjugates reveals that they possess drug-like properties.
Synthesis of arylpyrazole linked benzimidazole conjugates as potential microtubule disruptors
In an attempt to develop potent and selective anticancer agents, a series of twenty arylpyrazole linked benzimidazole conjugates (10a–t) were designed and synthesized as microtubule destabilizing agents. The joining of arylpyrazole to the benzimidazole moiety resulted in a four ring (A, B, C and D) molecular scaffold that comprises of polar heterocyclic rings in the middle associated with rotatable single bonds and substituted aryl rings placed in the opposite directions. These conjugates were evaluated for their ability to inhibit the growth of sixty cancer cell line panel of the NCI. Among these some conjugates like 10a, 10b, 10d, 10e, 10p and 10r exhibited significant growth inhibitory activity against most of the cell lines ranging from 0.3 to 13 lM. Interestingly, the conjugate 10b with methoxy group on D-ring expressed appreciable cytotoxic potential. A549 cells treated with some of the potent conjugates like 10a, 10b and 10d arrested cells at G2/M phase apart from activating cyclin-B1 protein levels and disrupting microtubule network. Moreover, these conjugates effectively inhibited tubulin polymerization with IC50 values of 1.3–3.8 lM. Whereas, the caspase assay revealed that they activate the casepase-3 leading to apoptosis. Particularly 10b having methoxy substituent induced activity almost 3 folds higher than CA- 4. Furthermore, a competitive colchicine binding assay and molecular modeling analysis suggests that these conjugates bind to the tubulin successfully at the colchicine binding site. These investigations reveal that such conjugates having pyrazole and benzimidazole moieties have the potential in the development of newer chemotherapeutic agents
A number of pyrazole–oxadiazole conjugates were synthesized and evaluated for their ability to function as antiproliferative agents on various human cancer cell lines. These conjugates are comprised of pyrazole and oxadiazole scaffolds closely attached to each other without any spacer as two structural classes. The Type I class has a trimethoxy substituent and the type II class has a 3,4-(methylenedioxy) substituent on their A rings. Among these conjugates, 11a, 11d and 11f manifest potent cytotoxicity with IC50 values ranging from 1.5 μM to 11.2 μM and inhibit tubulin polymerization with IC50 values of 1.3 μM, 3.9 μM and 2.4 μM respectively. The cell cycle assay showed that treatment with these conjugates results in accumulation of cells in the G2/M phase and disrupts the microtubule network. Elucidation of zebrafish embryos revealed that the conjugates cause developmental defects. Molecular docking simulations determined the binding modes of these potent conjugates at the colchicine site of tubulin.
A series of twenty one compounds with pyrazole and oxindole conjugates were synthesized by Knoevenagel condensation and investigated for their antiproliferative activity on different human cancer cell lines. The conjugates are comprised of a four ring scaffold; the structural isomers 12b and 12c possess chlorosubstitution in the D ring. Among the congeners 12b, 12c, and 12d manifested significant cytotoxicity and inhibited tubulin assembly. Treatments with 12b, 12c and 12d resulted in accumulation of cells in G2/M phase, disruption of microtubule network, and increase in cyclin B1 protein. Zebrafish screening revealed that 12b, and 12d caused developmental defects. Docking analysis demonstrated that the congeners occupy the colchicine binding pocket of tubulin.
Bioorganic & Medicinal Chemistry, 2009
A series of 3,4,6-triaryl-2-pyranones, new class of anti-breast cancer agents, have been synthesized as a structural variants of cyclic triphenylethylenes by replacing the fused benzene ring with pendant phenyl ring to mimic the phenolic A ring of estradiol. Nine of these newly synthesized pyranones exhibited significant anti-proliferative activity in both ER+ve and ERÀve breast cancer cell lines. Four active non-cytotoxic compounds 5c, 5d, 5g and 5h showed specific and selective cytotoxicity and two compounds 5d and 5h induced significant DNA fragmentation in both MCF-7 and MDA-MB-231 cell lines. Based on RBA studies, the molecules probably act in an ER-independent mechanism. The involved pathway was observed as caspase-dependant apoptosis in MCF-7 cells. However, the particular caspases involved and the possible cellular target through which this series of compounds mediate cell death are not known.
Journal of natural products, 2013
Alternariol and monomethylalternariol are natural phytotoxins produced by some fungal strains, such as Nimbya and Alternaria. These substances confer virulence to phytopathogens, yet no information is available concerning their mode of action. Here we show that in the micromolar range alternariol 9-methyl ether is able to inhibit the electron transport chain (IC50 = 29.1 ± 6.5 μM) in isolated spinach chloroplasts. Since its effectiveness is limited by poor solubility in water, several alternariol analogues were synthesized using different aromatic aldehydes. The synthesized 6H-benzo[c]cromen-6-ones, 5H-chromene[4,3-b]pyridin-5-one, and 5H-chromene[4,3-c]pyridin-5-one also showed inhibitory properties, and three 6H-benzo[c]cromen-6-ones were more effective (IC50 = 12.8-22.8 μM) than the lead compound. Their addition to the culture medium of a cyanobacterial model strain was found to inhibit algal growth, with a relative effectiveness that was consistent with their activity in vitro. ...
European Journal of Medicinal Chemistry, 2005
Nine new (±)-8-alkyl-5,7-dihydroxy-4-(4-hydroxyphenyl)-3,4-dihydrocoumarins have been synthesized from 2,4,6-trimethoxybenzaldehyde via a short, efficient, and regioselective pathway, together with the unsubstituted analogue (±)-5,7-dihydroxy-4-(4-hydroxyphenyl)-3,4dihydrocoumarin. The compounds were tested for estrogenic activity using a yeast-based estrogen screen. Weak estrogenicity was determined for seven members of the series.
2-Aminothienopyridazines as Novel Adenosine A 1 Receptor Allosteric Modulators and Antagonists
Journal of Medicinal Chemistry, 2008
A pharmacophore-based screen identified 32 compounds including ethyl 5-amino-3-(4-tertbutylphenyl)-4-oxo-3,4-dihydrothieno[3,4-d]pyridazine-1-carboxylate (8) as a new allosteric modulator of the adenosine A 1 receptor (A 1 AR). On the basis of this lead, various derivatives were prepared and evaluated for activity at the human A 1 AR. A number of the test compounds allosterically stabilized agonist-receptor-G protein ternary complexes in dissociation kinetic assays, but were found to be more potent as antagonists in subsequent functional assays of ERK1/2 phosphorylation. Additional experiments on the most potent antagonist, 13b, investigating A 1 ARmediated [ 35 S]GTPγS binding and [ 3 H]CCPA equilibrium binding confirmed its antagonistic mode of action and also identified inverse agonism. This study has thus identified a new class of A 1 AR antagonists that can also recognize the receptor's allosteric site with lower potency.
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