Development of novel 9H-carbazole-4H-chromene hybrids as dual cholinesterase inhibitors for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease affecting mental ability and neurocognitive functions. Cholinesterase enzymes affect concentration of acetylcholine in the brain, leading to dementia. Thus, there is an urgent need to develop novel dual cholinesterase inhibitors as possible anti-AD drugs. Herein, we have designed and synthesized a novel series of 9H-carbazole-4H-chromenes 4(a-l) through a one-pot three-component reaction of salicylaldehydes (1), hydroxycarbazole (2) and N-methyl-1-(methylthio)-2-nitroethenamine (3) using triethylamine as a catalyst in ethanol. Synthetic transformation involves the formation of two C-C bonds and one C-O bond in a single step to obtain desired analogs. The rapid one-pot reaction does not require chromatographic purification, proceeds under mild conditions, and exhibits good tolerance toward various functional groups with high synthetic yields. Synthesized compounds were screened for cytotoxicity using MTT assay in BV-2 microglial cells. These compounds were then in-vitro screened against acetylcholinesterase (AChE) and butyrylcholinestrase (BuChE) enzymes. Most of these ligands have shown dual cholinesterase inhibitory activity compared to the standard drug. In-vitro results showed that the compounds 4a and 4d have promising anticholinesterase response against both cholinesterase enzymes (4a, AChE IC50: 5.76 µM, BuChE IC50: 48.98 µM; 4d, AChE IC50: 3.58 µM, BuChE IC50: 42.73 µM). In-vitro results were validated by molecular docking and dynamic simulation at 100 ns. Molecular docking and molecular dynamics simulation study strongly supported structural features present in these analogs. Together, these analogs could be exploited to develop dual anti-cholinesterase candidates to treat AD in combination with other drugs.

Pd-catalyzed three-component [2 + 2 + 1] cycloamination toward carbazoles

Conventional approaches using hydroxylamine derivatives as single nitrogen sources for the preparation of N-heterocyclic molecules rely on two chemical processes involving sequential nucleophilic and electrophilic C-N bond formations. Herein, we report a novel Suzuki reaction/C-H activation/amination sequence for building a myriad of carbazoles in a single transformation using bifunctional secondary hydroxylamines. It is noteworthy that the synthetic utility of this methodology is highlighted by the total synthesis of clausine V and glycoborine by incorporating the title [2 + 2 + 1] cycloamination as the key step. Control experiments were performed to gain a better understanding of the reaction mechanism.

5,8-Dimethyl-9H-carbazole Derivatives Blocking hTopo I Activity and Actin Dynamics

Over the years, carbazoles have been largely studied for their numerous biological properties, including antibacterial, antimalarial, antioxidant, antidiabetic, neuroprotective, anticancer, and many more. Some of them have gained great interest for their anticancer activity in breast cancer due to their capability in inhibiting essential DNA-dependent enzymes, namely topoisomerases I and II. With this in mind, we studied the anticancer activity of a series of carbazole derivatives against two breast cancer cell lines, namely the triple negative MDA-MB-231 and MCF-7 cells. Compounds 3 and 4 were found to be the most active towards the MDA-MB-231 cell line without interfering with the normal counterpart. Using docking simulations, we assessed the ability of these carbazole derivatives to bind human topoisomerases I and II and actin. In vitro specific assays confirmed that the lead compounds selectively inhibited the human topoisomerase I and interfered with the normal organization of the actin system, triggering apoptosis as a final effect. Thus, compounds 3 and 4 are strong candidates for further drug development in multi-targeted therapy for the treatment of triple negative breast cancer, for which safe therapeutic regimens are not yet available.

Nitrogen Containing Heterocycles as Anticancer Agents: A Medicinal Chemistry Perspective

Cancer is one of the major healthcare challenges across the globe. Several anticancer drugs are available on the market but they either lack specificity or have poor safety, severe side effects, and suffer from resistance. So, there is a dire need to develop safer and target-specific anticancer drugs. More than 85% of all physiologically active pharmaceuticals are heterocycles or contain at least one heteroatom. Nitrogen heterocycles constituting the most common heterocyclic framework. In this study, we have compiled the FDA approved heterocyclic drugs with nitrogen atoms and their pharmacological properties. Moreover, we have reported nitrogen containing heterocycles, including pyrimidine, quinolone, carbazole, pyridine, imidazole, benzimidazole, triazole, β-lactam, indole, pyrazole, quinazoline, quinoxaline, isatin, pyrrolo-benzodiazepines, and pyrido[2,3-d]pyrimidines, which are used in the treatment of different types of cancer, concurrently covering the biochemical mechanisms of action and cellular targets.

Structural diversity-guided optimization of carbazole derivatives as potential cytotoxic agents

Carbazole alkaloids, as an important class of natural products, have been widely reported to have extensive biological activities. Based on our previous three-component reaction to construct carbazole scaffolds, we introduced a methylene group to provide a rotatable bond, and designed series of carbazole derivatives with structural diversity including carbazole amide, carbazole hydrazide and carbazole hydrazone. All synthesized carbazole derivatives were evaluated for their in vitro cytotoxic activity against 7901 (gastric adenocarcinoma), A875 (human melanoma) and MARC145 (African green monkey kidney) cell lines. The preliminary results indicated that compound 14a exhibited high inhibitory activities on 7901 and A875 cancer cells with the lowest IC₅₀ of 11.8 ± 1.26 and 9.77 ± 8.32 μM, respectively, which might be the new lead compound for discovery of novel carbazole-type anticancer agents.

Novel nitric oxide-releasing derivatives of pyranocarbazole as antitumor agents: Design, synthesis, biological evaluation, and nitric oxide release studies

In this study, a series of novel furoxan-based nitric oxide (NO) releasing derivatives of pyranocarbazole alkaloids were designed, synthesized, and biologically evaluated against human cancer cell lines. The derivatives showed considerable antiproliferative activities (IC50 = 0.05-7.55 μM) and most compounds showed higher activity in MDA-MB-231 than H460 and HeLa. Especially, the most active derivative 7a (IC50 = 0.05 μM) against MDA-MB-231 was about 60 times stronger than lead compound, as well as equivalent to positive control taxol, and produced high levels of NO in MDA-MB-231. Furthermore, 7a could significantly inhibit the growth of MDA-MB-231 tumors in vivo with low toxicity and the PI3K/Akt signaling pathway. These results indicated that compound 7a could be a promising lead for further studies.

New Heterocyclic Combretastatin A-4 Analogs: Synthesis and Biological Activity of Styryl-2(3H)-benzothiazolones

Here, we describe the synthesis, characterization, and biological activities of a series of 26 new styryl-2(3H)-benzothiazolone analogs of combretastatin-A4 (CA-4). The cytotoxic activities of these compounds were tested in several cell lines (EA.hy926, A549, BEAS-2B, MDA-MB-231, HT-29, MCF-7, and MCF-10A), and the relations between structure and cytotoxicity are discussed. From the series, compound (Z)-3-methyl-6-(3,4,5-trimethoxystyryl)-2(3H)-benzothiazolone (26Z) exhibits the most potent cytotoxic activity (IC50 0.13 ± 0.01 µM) against EA.hy926 cells. 26Z not only inhibits vasculogenesis but also disrupts pre-existing vasculature. 26Z is a microtubule-modulating agent and inhibits a spectrum of angiogenic events in EA.hy926 cells by interfering with endothelial cell invasion, migration, and proliferation. 26Z also shows anti-proliferative activity in CA-4 resistant cells with the following IC50 values: HT-29 (0.008 ± 0.001 µM), MDA-MB-231 (1.35 ± 0.42 µM), and MCF-7 (2.42 ± 0.48 µM). Cell-cycle phase-specific experiments show that 26Z treatment results in G2/M arrest and mitotic spindle multipolarity, suggesting that drug-induced centrosome amplification could promote cell death. Some 26Z-treated adherent cells undergo aberrant cytokinesis, resulting in aneuploidy that perhaps contributes to drug-induced cell death. These data indicate that spindle multipolarity induction by 26Z has an exciting chemotherapeutic potential that merits further investigation.

A Nitrocarbazole as a New Microtubule-Targeting Agent in Breast Cancer Treatment

Breast cancer is still considered a high-incidence disease, and numerous are the research efforts for the development of new useful and effective therapies. Among anticancer drugs, carbazole compounds are largely studied for their anticancer properties and their ability to interfere with specific targets, such as microtubule components. The latter are involved in vital cellular functions, and the perturbation of their dynamics leads to cell cycle arrest and subsequent apoptosis. In this context, we report the anticancer activity of a series of carbazole analogues 1–8. Among them, 2-nitrocarbazole 1 exhibited the best cytotoxic profile, showing good anticancer activity against two breast cancer cell lines, namely MCF-7 and MDA-MB-231, with IC50 values of 7 ± 1.0 and 11.6 ± 0.8 μM, respectively. Furthermore, compound 1 did not interfere with the growth of the normal cell line MCF-10A, contrarily to Ellipticine, a well-known carbazole derivative used as a reference molecule. Finally, in vitro immunofluorescence analysis and in silico studies allowed us to demonstrate the ability of compound 1 to interfere with tubulin organization, similarly to vinblastine: a feature that results in triggering MCF-7 cell death by apoptosis, as demonstrated using a TUNEL assay.

A novel histone deacetylase inhibitor LT-548-133-1 induces apoptosis by inhibiting HDAC and interfering with microtubule assembly in MCF-7 cells

Many studies have indicated that histone deacetylase inhibitors (HDACis) have a significant antitumor effect in cancer. Here we report a compound named LT-548-133-1 that not only acts as an HDAC inhibitor but also interferes with microtubule assembly to inhibit MCF-7 cell proliferation and induce apoptosis. Consistent with Chidamide, LT-548-133-1 inhibited HDAC activity and increased histone H3 acetylation. But the difference is that it significantly induced cell cycle G2/M arrest while Chidamide caused G0/G1 arrest in MCF-7 cells. By Western blotting, we found the accumulation of CyclinB1 and phosphorylated histone H3 in LT-548-133-1 treated cells. Immunofluorescence based microtubule-repolymerization experiments and immunofluorescence staining of cell microtubules and nuclei showed that LT-548-133-1inhibited microtubule-repolymerization and induced mitotic abnormalities. The decreased expression of Bcl-2 and the increased expression of Bax, p53, p21, and cleaved-Caspase3 indicated the occurrence of apoptosis. Flow cytometry results also showed an increase in the proportion of apoptotic cells after administration of LT-548-133-1 or Chidamide. Therefore, we demonstrated that LT-548-133-1 could act as an HDAC inhibitor while inhibiting microtubule-repolymerization, causing mitosis to be arrested in G2/M. These two effects ultimately lead to proliferation inhibition and apoptosis of MCF-7 cells.

Synthesis and biological evaluation of pyranocarbazole derivatives as Anti-tumor agents

A series of pyrano[3,2-a]carbazole alkaloids were designed and synthesized as derivatives of Girinimbine. The anticancer activities of these derivatives (3, 4a-j, 5a, 5c, 5f, 5i, 6c, 7a, 7c, 7f, 7i) against 10 cancer cell lines were studied. Among them, compounds 3 and 7i with N-methyl piperazine showed significant anticancer activity against MCF-7 cell lines with the IC50 values of 1.77 and 4.32 μM, respectively. Furthermore, their effects on altering cell morphology, inducing cell cycle arrest and apoptosis in MCF-7 cells were studied in vitro. In addition, the molecular docking study was carried out by using Discovery Studio software to predict the interactions between these derivatives and tubulin. All in all, these consequences reveal that pyranocarbazole derivatives with N-methyl piperazine can be used as potential anticancer lead compounds and provide useful points for the further optimization of pyranocarbazole alkaloids.

Synthesis and pharmacological properties of polysubstituted 2-amino-4H-pyran-3-carbonitrile derivatives

2-Amino-3-cyano-4H-chromenes are structural core motifs that received increasing attention in the last years due to their interesting potential pharmacological properties. In this review, the synthetic methods for these compounds are classified based on the type of catalyst in the pertinent reactions. In addition, the wide range of pharmacological properties of these compounds is covered in a separate section.

Carbazole scaffolds in cancer therapy: a review from 2012 to 2018

For over half a century, the carbazole skeleton has been the key structural motif of many biologically active compounds including natural and synthetic products. Carbazoles have taken an important part in all the existing anti-cancer drugs because of their discovery from a large variety of organisms, including bacteria, fungi, plants, and animals. In this article, we specifically explored the literature from 2012 to 2018 on the anti-tumour activities reported to carbazole derivatives and we have critically collected the most significant data. The most described carbazole anti-tumour agents were classified according to their structure, starting from the tricyclic–carbazole motif to fused tetra-, penta-, hexa- and heptacyclic carbazoles. To date, three derivatives are available on the market and approved in cancer therapy.

Design, synthesis and biological evaluation of novel pyrazolochalcones as potential modulators of PI3K/Akt/mTOR pathway and inducers of apoptosis in breast cancer cells

Cancer has been established as the "Emperor of all maladies". In recent years, medicinal chemistry has focused on identifying novel anti-cancer compounds; though discovery of these compounds appears to be a herculean task. In present study, we synthesized forty pyrazolochalcone conjugates and explored their cytotoxic activity against a panel of sixty cancer cell lines. Fifteen conjugates of the series showed excellent growth inhibition (13b-e, 13h-j, 14c-d, 15 a, 15 c-d, 16b, 16d and 18f; GI₅₀ for MCF-7: 0.4-20 μM). Conjugates 13b, 13c, 13d, 16b and 14d were also evaluated for their cytotoxic activity in human breast cancer cell line (MCF-7). The promising candidates induced cell cycle arrest, mitochondrial membrane depolarization and apoptosis in MCF-7 cells at a 2 μM concentration. Furthermore, inhibition of PI3K/Akt/mTOR pathway-regulators such as PI3K, p-PI3K, p-AKT, and mTOR were observed; as well as upregulation of p-GSK3β and tumor-suppressor protein, PTEN. Our study indicates that pyrazolochalcone conjugates could serve as potential leads in the development of tailored cancer therapeutics.

The milk-derived fusion peptide, ACFP, suppresses the growth of primary human ovarian cancer cells by regulating apoptotic gene expression and signaling pathways

Background

ACFP is an anti-cancer fusion peptide derived from bovine milk protein. This study was to investigate the anti-cancer function and underlying mechanisms of ACFP in ovarian cancer.

Methods

Fresh ovarian tumor tissues were collected from 53 patients who underwent initial debulking surgery, and primary cancer cells were cultured. Normal ovarian surface epithelium cells (NOSECs), isolated from 7 patients who underwent surgery for uterine fibromas, were used as normal control tissue. Anti-viabilities of ACFP were assessed by WST-1 (water-soluble tetrazolium 1), and apoptosis was measured using a flow cytometry-based assay. Gene expression profiles of ovarian cancer cells treated with ACFP were generated by cDNA microarray, and the expression of apoptotic-specific genes, such as bcl-xl, bax, akt, caspase-3, CDC25C and cyclinB1, was assessed by real time PCR and western blot analysis.

Results

Treatment with ACFP inhibited the viability and promoted apoptosis of primary ovarian cancer cells but exhibited little or no cytotoxicity toward normal primary ovarian cells. Mechanistically, the anti-cancer effects of ACFP in ovarian cells were shown to occur partially via changes in gene expression and related signal pathways. Gene expression profiling highlighted that ACFP treatment in ovarian cancer cells repressed the expression of bcl-xl, akt, CDC25C and cyclinB1 and promoted the expression of bax and caspase-3 in a time- and dose-dependent manner.

Conclusions

Our results suggest that ACFP may represent a potential therapeutic agent for ovarian cancer that functions by altering the expression and signaling of cancer-related pathways in ovarian cancer cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2281-6) contains supplementary material, which is available to authorized users.

Nano-cuprous oxide catalyzed one-pot synthesis of a carbazole-based STAT3 inhibitor: a facile approach via intramolecular C–N bond formation reactions

In this study, we report the one-pot synthesis of substituted carbazole derivatives using nano cuprous oxide as a catalyst and demonstrated the STAT3 inhibitory activity of new compounds.

Synthesis, molecular docking and in vitro antiproliferative activity of novel pyrano[3,2-c]carbazole derivatives

A new series of polycyclic pyrano[3,2-c]carbazole derivatives were synthesized, of which three compounds displayed pronounced antiproliferative activity on cancer cells.

In vitro anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit

The present study was undertaken to investigate the anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit and to explore the molecular mechanisms of action in MCF-7 cells. Cytotoxic properties of hexane, ethyl acetate and methanol extracts were carried out against MCF-7 cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Ethyl acetate extract showed good cytototoxic activities compared to hexane and methanol extracts. Methyl caffeate was isolated from the ethyl acetate extract using column chromatography. Cytotoxic properties of methyl caffeate was investigated against MCF-7, A549, COLO320, HepG-2 and Vero cells. The compound showed potent cytotoxic properties against MCF-7 cells compared to A549, COLO320 and HepG-2 cells. Methyl caffeate significantly reduced cell proliferation and increased formation of fragmented DNA and apoptotic body in MCF-7 cells. Bcl-2, Bax, Bid, p53, caspase-3, PARP and cytochrome c release were detected by western blot analysis. The activities of caspases-3 and PARP gradually increased after the addition of isolated compound. Bcl-2 protein was down regulated; Bid and Bax were up regulated after the treatment with methyl caffeate. Molecular docking studies showed that the compound bound stably to the active sites of poly (ADP-ribose) polymerase-1 (PARP1), B cell CLL/lymphoma-2 (BCL-2), E3 ubiquitin-protein ligase (MDM2) and tubulin. The results strongly suggested that methyl caffeate induced apoptosis in MCF-7 cells via caspase activation through cytochrome c release from mitochondria.

4-Alkylated Silver-N-Heterocyclic Carbene (NHC) Complexes with Cytotoxic Effects in Leukemia Cells

Computational chemistry has shown that backbone-alkylated imidazoles ought to be efficient ligands for transition metal catalysts with improved carbene-to-metal donation. In this work, such alkylated imidazoles were synthesized and complexed with silver(I) by means of an eight/nine-step synthetic pathway we devised to access a new class of biologically active silver complexes. The synthesis involves selective iodination of the imidazole backbone, followed by Sonogashira coupling to replace the backbone iodine. The installed alkyne moiety is then subjected to reductive hydrogenation with Pearlman's catalyst. The imidazole N1 atom is arylated by the palladium-catalyzed Buchwald N-arylation method. The imidazole N3 position was then methylated with methyl iodine, whereupon the synthesis was terminated by complexation of the imidazolium salt with silver(I) oxide. The synthetic pathway provided an overall yield of ≈20 %. The resulting complexes were tested in vitro against HL60 and MOLM-13 leukemic cells, two human-derived cell lines that model acute myeloid leukemia. The most active compounds exhibiting low IC50 values of 14 and 27 μM, against HL60 and MOLM-13 cells, respectively. The imidazole side chain was found to be essential for high cytotoxicity, as the imidazole complex bearing a C7 side chain at the 4-position was four- to sixfold more potent than the corresponding imidazole elaborated with a methyl group.

Palladium-catalyzed arylation of 2H-chromene: a new entry to pyrano[2,3-c]carbazoles

Various pyrano[2,3-c]carbazoles are synthesized in high yields over five steps from commercially available resorcinol. Palladium-catalyzed arylation remains a key step in this novel strategy. The versatility of this protocol has been demonstrated by the first total synthesis of naturally occurring carbazole clauraila C.