Synthesis of imidazo-thiadiazole linked indolinone conjugates and evaluated their microtubule network disrupting and apoptosis inducing ability.

A series of imidazo[2,1-b][1,3,4]thiadiazole linked indolinone conjugates were synthesized and investigated for antiproliferative activity in different human cancer cell lines by changing various substitutions at indolinone and phenyl ring systems. Among them conjugates 7, 14 and 15 were exhibited potent antiproliferative activity with GI50 values from 0.13 to 3.8 µΜ and evaluated for cell cycle analysis, tubulin polymerization assay and apoptosis. Treatment with 7, 14 and 15 were resulted in accumulation of cells in G2/M phase, inhibition of tubulin assembly, disruption of microtubule network. Inhibition of tubulin polymerization was further supported by Western blot analysis. In addition, the conjugates (7, 14 and 15) also showed apoptosis in HeLa cell line, detailed biological studies such as Hoechst 33,258 staining, DNA fragmentation and caspase-3 assays suggested that these compounds induce cell death by apoptosis. Docking studies revealed that these compounds (7, 14 and 15) bind with αAsn101, αThr179, αSer178, ßCys241, ßLys254 and ßLys352 in the colchicine-binding site of the tubulin.

Synthesis of novel tetrazole containing hybrid ciprofloxacin and pipemidic acid analogues and preliminary biological evaluation of their antibacterial and antiproliferative activity.

A series of 1-substituted-1H-tetrazole-5-thiol building blocks were synthesized and introduced to the N-4 piperazinyl group at C-7 position of the quinolone core, and these novel compounds (5a-g and 8a-g) were screened for their antibacterial and antiproliferative activities. Bioactive assay studies manifested that most of new compounds exhibited significant antibacterial activity against the tested strains, including multi-drug-resistant MRSA in comparison with reference drugs ciprofloxacin, streptomycin B and pipemidic acid. Among the synthesized compounds, only ciprofloxacin (5a-g) derivatives displayed significant activity ([Formula: see text]) compared to reference drugs. In addition, these compounds were evaluated for their in vitro inhibition of human cancer cell lines viz human cervical carcinoma cell line (SiHA), breast adenocarcinoma (MDA-MB-235) and human pancreas carcinoma (PANC-1) cell lines by using the SRB assay method. Most of the target compounds showed broad potent growth inhibition activity ([Formula: see text]) against all the tested cancer cell lines compared with reference drug. The most promising active compounds in this series were 5c, 5d, 8c, 8d and 8f endowed with excellent antiproliferative activity. A new class of compounds was designed rationally by introducing tetrazole building block on N-4 piperazinyl group at C-7 position of quinolones core. The titled compounds were evaluated for their preliminary antibacterial and antiproliferative activities.

Potential anti-proliferative agents from 1,4-benzoxazinone-quinazolin-4(3H)-one templates.

A novel synthetic protocol has been developed for the synthesis of 1,4-benzoxazinone-acetylphenylallyl quinazolin-4(3H)-one hybrids 7a-n by employing Pd-catalyzed CH arylation in presence of 5-10% phosphine ligand in good to excellent yields and evaluated for their anti-proliferative activity against three cancer cell lines such as A549 (lung), HeLa (cervical), MDA-MB-231 (breast). Compounds 7d, 7f, 7l and 7n exhibited promising anti-proliferative activity with GI50 values ranging from 0.37 to 2.73 µM respectively against A549, HeLa, and MDA-MB-231, while compound 7f showed significant activity against MDA-MB-231 with GI50 value 0.58 µM, 7j showed significant activity against A549 with GI50 value 0.32 µM and 7l showed significant activity against HeLa with GI50 value 0.37 µM. This is the first report on the synthesis and in vitro anti-proliferative evaluation of 1,4-benzoxazinone-acetylphenylallyl quinazolin-4(3H)-one hybrids.

Design, synthesis and docking studies of novel 1,2-dihydro-4-hydroxy-2-oxoquinoline-3-carboxamide derivatives as a potential anti-proliferative agents.

A new series of 4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinoline-3-carboxamide hybrids 8a-l have been designed and synthesized using peptide coupling agents with substituted N-phenyl piperazines and piperidines with good to excellent yields. The synthesized compounds were evaluated for their in vitro anti-proliferative activity against PANC 1, HeLa and MDA-MB-231. The compounds 8d, 8e, 8f, 8g, 8h and 8k exhibited considerable anti-proliferative activity with GI50 values ranging from 0.15 to 1.4 µM. The structure and anti-proliferative activity relationship was further supported by in silico molecular docking study of the active compounds against tubulin protein.

Synthesis and biological evaluation of novel tamoxifen-1,2,4-triazole conjugates.

A new class of compounds, structurally related to the breast cancer drug tamoxifen, was designed and synthesized. The McMurry coupling reaction was used as the key synthetic step in the preparation of these analogs, and the structural assignments were made on the basis of [Formula: see text] NMR, [Formula: see text] NMR, and HRMS studies. The absolute stereochemistry of E and Z isomers was unambiguously confirmed by a single-crystal X-ray diffraction analysis. Water was found to be an inexpensive nontoxic and effective medium for the C-N bond formation. Utilizing this protocol, various tamoxifen derivatives were synthesized in good yields. Environmental acceptability, low cost, and high yields are the important features of this protocol. These compounds were evaluated for their antiproliferative activity on five human tumor cell lines. Compound 4p ([Formula: see text]) showed improved antiproliferative activity against breast cancer cell line (MDA-MB-231) compared to tamoxifen ([Formula: see text]), while the compound 4o ([Formula: see text]) exhibited similar activity against SiHa compared to the reference drug, tamoxifen ([Formula: see text]). In addition, these analogs were investigated for their antibacterial activity against six bacterial strains. Preliminary results indicate that some of the newly synthesized title compounds exhibited promising antibacterial activity compared with the standard drug, vancomycin. A new class of compounds were designed rationally by the replacement of a ethyl group in tamoxifen with a methylene (1H-1,2,4-triazole) group. The absolute stereochemistry of E and Z isomers were unambiguously confirmed by a single-crystal X-ray diffraction analysis. The title compounds were evaluated for their antiproliferative and antibacterial activities.

Quinazolinones-Phenylquinoxaline hybrids with unsaturation/saturation linkers as novel anti-proliferative agents.

A new series of novel quinazolinones with allylphenyl quinoxaline hybrids 9a-n were efficiently synthesized in good yields by the reaction of 3-allyl-2-methylquinazolin-4(3H)-one (5a-n) with bromophenyl)quinoxaline (8) utilizing Pd catalyzed Heck-cross coupling and evaluated for anti-proliferative activity against four cancer cell lines such as HeLa (cervical), MIAPACA (pancreatic), MDA-MB-231 (breast) and IMR32 (neuroblastoma). Compounds 9a, 9e, 9g and 9h exhibited promising anti-proliferative activity with GI50 values ranging from 0.06 to 0.2µM against four cell lines, while compounds 9e and 9k showed significant activity against HeLa and MIAPACA cell lines and compounds 9b, 9d, 9h and 9j showed selective potency against IMR32 and MDA-MB-231 cell lines. This is the first report on the synthesis and in vitro anti-proliferative evaluation of E-2-(4-substituted)-3-(3-(4-(quinoxalin-2-yl)phenyl)allyl)quinazolin-4(3H)-ones (9a-n). Docking results indicate a sign of good correlation between experimental activity and calculated binding affinity (dock score), suggesting that these compounds could act as promising DNA intercalates.

Synthesis and antiproliferative activity of imidazo[1,2-a]pyrimidine Mannich bases.

A series of imidazo[1,2-a]pyrimidine Mannich bases were designed, synthesized in two phases. Mannich bases were obtained by one pot three component condensation of imidazo[1,2-a]pyrimidine with secondary amine or piperazine and excess of formaldehyde solution in methanol. The synthesized Mannich bases were screened for in vitro growth inhibition against a panel of 3 different human cancer cell lines. Most of the synthesized compounds exhibited antiproliferative activity with GI50 values ranging from 0.01 to 79.4 µM. Compounds 5e, 6b and 7k were found to be effective inhibitors of growth of all cell lines, with GI50 values similar to that of standard drug. The structure and activity relationship has been disclosed.

Synthesis and evaluation of benzosuberone embedded with 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole moieties as new potential anti proliferative agents.

As an aspect of our ongoing research in search of new anti proliferative agents, a series of novel analogs of benzosuberone embedded with 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole moieties were synthesized in excellent yields (82-93%). All the newly synthesized compounds were characterized by (1)H NMR, (13)C NMR, ESI/LC-MS, HRMS and evaluated for their in vitro anti proliferative activity against four human cancer cell lines (cervical, breast, pancreatic and alveolar). Among the synthesized compounds, 4b, 6a, 7d and 7l showed potent anti proliferative activity with GI50 values range of 0.079-0.957µM against four human cancer cell lines. However, it was revealed that the compound 7d have shown very close GI50 value 0.079µM as compared with positive control of colchicine against cervical cancer cell line.

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 13µM. 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 1.3-3.8µM. 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.

Synthesis of (Z)-(arylamino)-pyrazolyl/isoxazolyl-2-propenones as tubulin targeting anticancer agents and apoptotic inducers.

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.

Rational design, synthesis and anti-proliferative evaluation of novel 1,4-benzoxazine-[1,2,3]triazole hybrids.

A series of novel 1,2,3-triazole-1,4-benzoxazine hybrids 5a-n were efficiently synthesized employing click chemistry approach and evaluated for anti-proliferative activity against four cancer cell lines such as HeLa (cervical), MIAPACA (pancreatic), MDA-MB-231 (breast) and IMR32 (neuroblastoma). Compounds 5n and 5g exhibited promising anti-proliferative activity with GI50 values ranging from 1.2 to 2.5 µM and 0.1-1.1 µM respectively against all cell lines, like HeLa, MDA-MB-231, MIAPACA and IMR32, while compound 5l showed significant activity against MDA-MB-231 and IMR32 with GI50 values ranging from 1.1 and 1.4 µM. This is the first report on the synthesis and in vitro anti-proliferative evaluation of 1,2,3-triazole-1,4-benzoxazine hybrids.

The protecting-group directed diastereoselective Nozaki-Hiyama-Kishi (NHK) reaction: total synthesis and biological evaluation of zeaenol, 7-epi-zeaenol and its analogues.

The stereoselective total synthesis of zeaenol and 7-epi-zeaenol is achieved in a convergent manner using Julia-Kocienski olefination, protecting group-directed intermolecular diastereoselective Nozaki-Hiyama-Kishi (NHK) reaction, De Brabander's lactonization reaction and CBS reduction as the key steps. In this article, we have observed the most suitable protecting groups with respect to selectivity during the protecting group directed intermolecular asymmetric Nozaki-Hiyama-Kishi reaction. The zeaenol, 7-epi-zeaenol and its derivatives were analyzed for their biological activity and screened in four cancer cell lines.

Pyrazole-oxadiazole conjugates: synthesis, antiproliferative activity and inhibition of tubulin polymerization.

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.

Design and synthesis of aminostilbene-arylpropenones as tubulin polymerization inhibitors.

A series of aminostilbene-arylpropenones were designed and synthesized by Michael addition and were investigated for their cytotoxic activity against various human cancer cell lines. Some of the investigated compounds exhibited significant antiproliferative activity against a panel of 60 human cancer cell lines of the US National Cancer Institute, with 50 % growth inhibition (GI50) values in the range from < 0.01 to 19.9 µM. One of the compounds showed a broad spectrum of antiproliferative efficacy on most of the cell lines, with a GI50 value of < 0.01 µM. All of the synthesized compounds displayed cytotoxicity against A549 (non-small-cell lung cancer), HeLa (cervical carcinoma), MCF-7 (breast cancer), and HCT116 (colon carcinoma) with 50 % inhibitory concentration (IC50) values ranging from 0.011 to 8.56 µM. A cell cycle assay revealed that these compounds arrested the G2/M phase of the cell cycle. Two compounds exhibited strong inhibitory effects on tubulin assembly with IC50 values of 0.71 and 0.79 µM. Moreover, dot-blot analysis of cyclin B1 demonstrated that some of the congeners strongly induced cyclin B1 protein levels. Molecular docking studies indicated that these compounds occupy the colchicine binding site of tubulin.

Synthesis and biological evaluation of podophyllotoxin congeners as tubulin polymerization inhibitors.

A series of new podophyllotoxin derivatives containing structural modifications at C-7, C-8, and C-9 were synthesized and evaluated for their cytotoxic activity against three human cancer cell lines. All the synthesized compounds showed significant growth inhibition with GI50 values in micromolar levels while some of the compounds were several times more potent against MCF-7 and HeLa cell lines than MIAPACA cell line. Three compounds (12a, 12d and 12e) emerged as potent compounds with broad spectrum of cytotoxic activity against all the tested cell lines with GI50 values in the range of 0.01-2.1 µM. These compounds induce microtubule depolymerization and arrests cells at the G2/M phase of the cell cycle. Moreover, compounds 12d and 12e disrupted microtubule network and accumulated tubulin in the soluble fraction in a similar manner to their parent podophyllotoxin scaffold. In addition, structure activity relationship studies within the series were also discussed. Molecular docking studies of these compounds into the colchicine-binding site of tubulin, revealed possible mode of inhibition by these compounds.

Synthesis and biological evaluation of 4-aza-2,3-dihydropyridophenanthrolines as tubulin polymerization inhibitors.

A series of novel 4-aza-2,3-dihydropyridophenanthrolines 12(a-t) were synthesized by a one-step three component condensation of 1,10-phenanthroline amine, tetronic acid and various aromatic aldehydes. These were evaluated for their antiproliferative activity against three human cancer cell lines (MIAPACA, MCF-7 and HeLa) using SRB assay. Majority of the tested compounds exhibited significant anticancer activity on these cell lines and interestingly compounds 12h and 12i were more potent than etoposide and podophyllotoxin against all three tested cancer cell lines with GI50 values in the range of 0.01-0.5 µM. Furthermore, these compounds showed significant inhibition of tubulin polymerization which is comparable to that of podophyllotoxin and disrupted microtubule network by accumulating tubulin in the soluble fraction. The flow cytometry analysis confirmed that the synthesized compounds led to cell cycle arrest at the G2/M phase. Moreover, the structure activity relationship studies in this series are also discussed.

Synthesis and biological evaluation of imidazo[2,1-b][1,3,4]thiadiazole-linked oxindoles as potent tubulin polymerization inhibitors.

A series of imidazo[2,1-b][1,3,4]thiadiazole-linked oxindoles composed of an A, B, C and D ring system were synthesized and investigated for anti-proliferative activity in various human cancer cell lines; test compounds were variously substituted at rings C and D. Among them, compounds 7 ((E)-5-fluoro-3-((6-p-tolyl-2-(3,4,5-trimethoxyphenyl)-imidazo[2,1-b][1,3,4]thiadiazol-5-yl)methylene)indolin-2-one), 11 ((E)-3-((6-p-tolyl-2-(3,4,5-trimethoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl)methylene)indolin-2-one), and 15 ((E)-6-chloro-3-((6-phenyl-2-(3,4,5-trimethoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl)methylene)indolin-2-one) exhibited potent anti-proliferative activity. Treatment with these three compounds resulted in accumulation of cells in G2 /M phase, inhibition of tubulin assembly, and increased cyclin-B1 protein levels. Compound 7 displayed potent cytotoxicity, with an IC50 range of 1.1-1.6 µM, and inhibited tubulin polymerization with an IC50 value (0.15 µM) lower than that of combretastatin A-4 (1.16 µM). Docking studies reveal that compounds 7 and 11 bind with αAsn101, ßThr179, and ßCys241 in the colchicine binding site of tubulin.