Novel indole-bearing combretastatin analogues as tubulin polymerization inhibitors

Synthesis, in vitro Α-Glucosidase, and acetylcholinesterase inhibitory activities of novel Indol-Fused Pyrano[2,3-D]Pyrimidine compounds

In this study, new indol-fused pyrano[2,3-d]pyrimidines were designed and synthesized. These products were obtained in moderate to good yields and their structures were assigned by NMR, MS, and IR analysis. Afterwards, the biological important of the products was highlighted by evaluating in vitro for α-glucosidase inhibitory activity as well as acetylcholinesterase (AChE) inhibitory activity. Eleven products revealed substantial inhibitory activity against α-glucosidase enzyme, among which, two most potent products 11d,e were approximately 93-fold more potent than acarbose as a standard antidiabetic drug. Besides that, product 11k exhibited good AChE inhibition. The substituents on the 5-phenyl ring, attached to the pyran ring, played a critical role in inhibitory activities. The biological potencies have provided an opportunity to further investigations of indol-fused pyrano[2,3-d]pyrimidines as potential anti-diabetic agents.

Nitrogen-Containing Heterocycles as Anticancer Agents: An Overview

Background:

Cancer is spreading all over the world, and it is becoming the leading cause of major deaths. Today’s most difficult task for every researcher is to invent a new drug that can treat cancer with minimal side effects. Many factors, including pollution, modern lifestyle and food habits, exposure to oncogenic agents or radiations, enhanced industrialization, etc. can cause cancer. Treatment of cancer is done by various methods that include chemotherapy, radiotherapy, surgery and immunotherapy in combination or singly along with kinase inhibitors. Most of the anti-cancer drugs use the concept of kinase inhibition.

Objective:

The number of drugs being used in chemotherapy has heterocycles as their basic structure in spite of various side effects. Medicinal chemists are focusing on nitrogen-containing heterocyclic compounds like pyrrole, pyrrolidine, pyridine, imidazole, pyrimidines, pyrazole, indole, quinoline, oxadiazole, azole, benzimidazole, etc. as the key building blocks to develop active biological compounds. The aim of this study is to attempt to compile a dataset of nitrogen-containing heterocyclic anti-cancer drugs.

Methods:

We adopted a structural search on notorious journal publication websites and electronic databases such as Bentham Science, Science Direct, PubMed, Scopus, USFDA, etc. for the collection of peer-reviewed research and review articles for the present review. The quality papers were retrieved, studied, categorized into different sections, analyzed and used for article writing.

Conclusion:

As per FDA databases, nitrogen-based heterocycles in the drug design are almost 60% of unique small-molecule drugs. Some of the nitrogen-containing heterocyclic anti-cancer drugs are Axitinib, Bosutinib, Cediranib, Dasatanib (Sprycel®), Erlotinib (Tarceva®), Gefitinib (Iressa®), Imatinib (Gleevec®), Lapatinib (Tykerb ®), Linifanib, Sorafenib (Nexavar®), Sunitinib (Sutent®), Tivozanib, etc. In the present review, we shall focus on the overview of nitrogen-containing heterocyclic active compounds as anti-cancer agents.

Beyond the Paclitaxel and Vinca Alkaloids: Next Generation of Plant-Derived Microtubule-Targeting Agents with Potential Anticancer Activity

Plants are an important source of chemically diverse natural products that target microtubules, one of the most successful targets in cancer therapy. Colchicine, paclitaxel, and vinca alkaloids are the earliest plant-derived microtubule-targeting agents (MTAs), and paclitaxel and vinca alkaloids are currently important drugs used in the treatment of cancer. Several additional plant-derived compounds that act on microtubules with improved anticancer activity are at varying stages of development. Here, we move beyond the well-discussed paclitaxel and vinca alkaloids to present other promising plant-derived MTAs with potential for development as anticancer agents. Various biological and biochemical aspects are discussed. We hope that the review will provide guidance for further exploration and identification of more effective, novel MTAs derived from plant sources.

De novo identification of toxicants that cause irreparable damage to parasitic nematode intestinal cells

Efforts to identify new drugs for therapeutic and preventive treatments against parasitic nematodes have gained increasing interest with expanding pathogen omics databases and drug databases from which new anthelmintic compounds might be identified. Here, a novel approach focused on integrating a pan-Nematoda multi-omics data targeted to a specific nematode organ system (the intestinal tract) with evidence-based filtering and chemogenomic screening was undertaken. Based on de novo computational target prioritization of the 3,564 conserved intestine genes in A. suum, exocytosis was identified as a high priority pathway, and predicted inhibitors of exocytosis were tested using the large roundworm (Ascaris suum larval stages), a filarial worm (Brugia pahangi adult and L3), a whipworm (Trichuris muris adult), and the non-parasitic nematode Caenorhabditis elegans. 10 of 13 inhibitors were found to cause rapid immotility in A. suum L3 larvae, and five inhibitors were effective against the three phylogenetically diverse parasitic nematode species, indicating potential for a broad spectrum anthelmintics. Several distinct pathologic phenotypes were resolved related to molting, motility, or intestinal cell and tissue damage using conventional and novel histologic methods. Pathologic profiles characteristic for each inhibitor will guide future research to uncover mechanisms of the anthelmintic effects and improve on drug designs. This progress firmly validates the focus on intestinal cell biology as a useful resource to develop novel anthelmintic strategies.

Synthesis and Evaluation of Antimicrobial Activities of Novel N-Substituted Indole Derivatives

Indole motifs are one of the most significant scaffolds in the discovery of new drugs. We have described a synthesis of new N-substituted indole derivatives (1-3), and their in vitro antimicrobial activities were investigated. The synthesis of titled compounds has been demonstrated by utilizing commercially available starting materials. The antibacterial and antifungal activities were performed using new strains of bacteria Staphylococcus aureus, Escherichia coli, and Candida albicans using the disc diffusion method. Notably, the compound 4-(1-(2-(1H-indol-1-yl) ethoxy) pentyl)-N,N-dimethyl aniline (1) was found to be most potent than the other analogues (2 and 3), which has shown higher inhibition than the standard drug chloramphenicol.

Design and Synthesis of Novel Cytotoxic Indole-Thiosemicarbazone Derivatives: Biological Evaluation and Docking Study

In this work, two novel series of indole-thiosemicarbazone derivatives were designed, synthesized, and evaluated for their cytotoxic activity against MCF-7, A-549, and Hep-G2 cell lines in comparison to etoposide and colchicine as the reference drugs. Generally, the synthesized compounds showed better cytotoxicity towards A-549 and Hep-G2 than MCF-7. Among them, (2E)-2-{[2-(4-chlorophenyl)-1H-indol-3-yl]methylidene}-N-(4-methoxyphenyl)hydrazinecarbothioamide (8l) was found to be the most potent compound against A-549 and Hep-G2, at least three times more potent than etoposide. The morphological analysis by the acridine orange/ethidium bromide double staining test and flow cytometry analysis indicated that compound 8l induced apoptosis in A-549 cells. Moreover, molecular docking methodology was exploited to elucidate the details of molecular interactions of the studied compounds with putative targets.

1-Arylsulfonyl indoline-benzamides as a new antitubulin agents, with inhibition of histone deacetylase

We report structure-activity relationships of 1-arylsulfonyl indoline based benzamides. The benzamide (9) exhibits striking tubulin inhibition with an IC₅₀ value of 1.1 μM, better than that of combretastain A-4 (3), and substantial antiproliferative activity against a variety of cancer cells, including MDR-positive cell lines with an IC₅₀ value of 49 nM (KB), 79 nM (A549), 63 nM (MKN45), 64 nM (KB-VIN10), 43 nM (KB-S15), and 46 nM (KB-7D). Dual inhibitory potential of compound 9 was found as it demonstrated significant inhibitory potential against HDAC1, 2 and 6 in comparison to MS-275 (6). Some key interactions of 9 with the amino acid residues of the active site of tubulin and with amino acid residues of HDAC 1 isoform have been figured out by molecular modeling. Compound 9 also demonstrated significant in vivo efficacy in the human non-small cell lung cancer A549 xenograft model as well as B-cell lymphoma BJAB xenograft tumor model.

Synthesis, Evaluation of Cytotoxicity and Molecular Docking Studies of the 7-Acetamido Substituted 2-Aryl-5-bromo-3-trifluoroacetylindoles as Potential Inhibitors of Tubulin Polymerization

The 3-trifluoroacetyl⁻substituted 7-acetamido-2-aryl-5-bromoindoles 5a⁻h were prepared and evaluated for potential antigrowth effect in vitro against human lung cancer (A549) and cervical cancer (HeLa) cells and for the potential to inhibit tubulin polymerization. The corresponding intermediates, namely, the 3-unsubstituted 7-acetyl-2-aryl-5-bromoindole 2a⁻d and 7-acetamido-2-aryl-5-bromoindole 4a⁻d were included in the assays in order to correlate both structural variations and cytotoxicity. No cytotoxicity was observed for compounds 2a⁻d and their 3-trifluoroacetyl⁻substituted derivatives 5a⁻d against both cell lines. The 7-acetamido derivatives 4⁻d exhibited modest cytotoxicity against both cell lines. All of the 3-trifluoroacetyl⁻substituted 7-acetamido-2-aryl-5-bromoindoles 5e⁻h were found to be more active against both cell lines when compared to the chemotherapeutic drug, Melphalan. The most active compound, 5g, induced programmed cell death (apoptosis) in a caspase-dependent manner for both A549 and HeLa cells. Compounds 5e⁻h were found to significantly inhibit tubulin polymerization against indole-3-carbinol and colchicine as reference standards. Molecular docking of 5g into the colchicine-binding site suggests that the compounds bind to tubulin by different type of interactions including pi-alkyl, amide-pi stacked and alkyl interactions as well as hydrogen bonding with the protein residues to elicit anticancer activity.

2,4-Diarylpyrano[3,2-c]chromen-5(4H)-ones as Antiproliferative Agents

In the present study, a series of 2,4-diarylpyrano[3,2-c]chromen-5(4H)-ones were synthesised and evaluated as antiproliferative agents. The compounds were evaluated against a panel of human cancer cell lines. CH-1 exhibited significant cytoxicity against HCT 116 cell lines with an IC50 value of 1.4 and 4.3 µM against "MiaPaCa-2" cell lines. The compound CH-1 was found to induce apoptosis as evidenced by phase contrast microscopy, Hoechst 33258 staining and mitochondrial membrane potential (MMP) loss. The cell phase distribution studies indicated that the apoptotic population increased from 10.22% in the control sample to 57.19% in a sample treated with 20 µM compound CH-1.

Combretastatins: In vitro structure-activity relationship, mode of action and current clinical status

For the first time combretastatins were isolated from African willow tree Combretum Caffrum. Subsequent studies have shown the impact of combretastatin A4 phosphate, a water-soluble prodrug, on endothelial cells in tumor vascular system. The same effect was not observed in the vascular system. This selectivity is associated with combretastatins mechanism of action: binding to colchicine domain of microtubules, which affects the cytoskeleton functionality of immature endothelial cells. At the same time, combretastatins directly induce cell death via apoptosis and/or mitotic catastrophe pathways. The combination of both elements makes combretastatin an anticancer compound of high efficiency. The cis-configuration is crucial for its biological activity. To date, many derivatives were synthesized. The attempts to resolve spontaneous isomerization to less active trans-stilbene derivative are still in progress. This issue seems to be overcome by incorporation of the ethene bridge with heterocyclic moiety in combretastatins structure. This modification retains the cis-configuration and prevents isomerization. Nevertheless, combretastatin A4 phosphate disodium is still the most potent compound of this group. The combination therapy, which is the most effective treatment, includes combretastatin A4 phosphate (CA4P) and conventional chemotherapeutics and/or radiotherapy. CA4P is relatively well tolerated giving adverse events of moderate severity, which includes: nausea, vomiting, headache, and tumor pain. The aforementioned effects subside on the day of drug administration or on the following day.

Triazole tethered C5-curcuminoid-coumarin based molecular hybrids as novel antitubulin agents: Design, synthesis, biological investigation and docking studies

Keeping in view the confines allied with presently accessible antitumor agents and success of C5-curcuminoid based bifunctional hybrids as novel antitubulin agnets, molecular hybrids of C5-curcuminoid and coumarin tethered by triazole ring have been synthesized and investigated for in-vitro cytotoxicity against THP-1, COLO-205, HCT-116 and PC-3 human tumor cell lines. The results revealed that the compounds A-2 to A-9, B-2, B-3, B-7 showed significant cytotoxic potential against THP-1, COLO-205 and HCT-116 cell lines, while the PC-3 cell line among these was found to be almost resistant. Structure activity relationship revealed that the nature of Ring X and the length of carbon-bridge (n) connecting triazole ring with coumarin moiety considerably influence the activity. Methoxy substituted phenyl ring as Ring X and two carbon-bridges were found to be the ideal structural features. The most potent compounds (A-2, A-3 and A-7) were further tested for tubulin polymerization inhibition. Compound A-2 was found to significantly inhibit the tubulin polymerization (IC50 = 0.82 μM in THP-1 tumor cells). The significant cytotoxicity and tubulin polymerization inhibition by A-2 was further rationalized by docking studies where it was docked at the curcumin binding site of tubulin.

Triazole linked mono carbonyl curcumin-isatin bifunctional hybrids as novel anti tubulin agents: Design, synthesis, biological evaluation and molecular modeling studies

Keeping in view the limitations associated with currently available anticancer drugs, molecular hybrids of mono carbonyl curcumin and isatin tethered by triazole ring have been synthesized and evaluated for in vitro cytotoxicity against THP-1, COLO-205, HCT-116, A549, HeLa, CAKI-I, PC-3, MiaPaca-2 human cancer cell lines. The results revealed that the compounds SA-1 to SA-9, SB-2, SB-3, SB-4, SB-7 and SC-2 showed a good range of IC50 values against THP-1, COLO-205, HCT-116 and PC-3 cell lines, while the other four cell lines among these were found to be almost resistant. Structure activity relationship revealed that the nature of Ring X and substitution at position R influences the activity. Methoxy substituted phenyl ring as Ring X and H as R were found to be the ideal structural features. The most potent compounds (SA-2, SA-3, SA-4, SA-7) were further tested for tubulin inhibition. Compound SA-2 was found to significantly inhibit the tubulin polymerization (IC50=1.2 μM against HCT-116). Compound SA-2, moreover, lead to the disruption of microtubules as confirmed by immunofluorescence technique. The significant cytotoxicity and tubulin inhibition by SA-2 was streamlined by molecular modeling studies where it was docked at the curcumin binding site of tubulin.

Stabilizing versus destabilizing the microtubules: a double-edge sword for an effective cancer treatment option?

Microtubules are dynamic and structural cellular components involved in several cell functions, including cell shape, motility, and intracellular trafficking. In proliferating cells, they are essential components in the division process through the formation of the mitotic spindle. As a result of these functions, tubulin and microtubules are targets for anticancer agents. Microtubule-targeting agents can be divided into two groups: microtubule-stabilizing, and microtubule-destabilizing agents. The former bind to the tubulin polymer and stabilize microtubules, while the latter bind to the tubulin dimers and destabilize microtubules. Alteration of tubulin-microtubule equilibrium determines the disruption of the mitotic spindle, halting the cell cycle at the metaphase-anaphase transition and, eventually, resulting in cell death. Clinical application of earlier microtubule inhibitors, however, unfortunately showed several limits, such as neurological and bone marrow toxicity and the emergence of drug-resistant tumor cells. Here we review several natural and synthetic microtubule-targeting agents, which showed antitumor activity and increased efficacy in comparison to traditional drugs in various preclinical and clinical studies. Cryptophycins, combretastatins, ombrabulin, soblidotin, D-24851, epothilones and discodermolide were used in clinical trials. Some of them showed antiangiogenic and antivascular activity and others showed the ability to overcome multidrug resistance, supporting their possible use in chemotherapy.

Heterocyclic Anticancer Compounds: Recent Advances and the Paradigm Shift towards the Use of Nanomedicine's Tool Box

The majority of heterocycle compounds and typically common heterocycle fragments present in most pharmaceuticals currently marketed, alongside with their intrinsic versatility and unique physicochemical properties, have poised them as true cornerstones of medicinal chemistry. Apart from the already marketed drugs, there are many other being investigated for their promising activity against several malignancies. In particular, anticancer research has been capitalizing on the intrinsic versatility and dynamic core scaffold of these compounds. Nevertheless, as for any other promising anticancer drugs, heterocyclic compounds do not come without shortcomings. In this review, we provide for a concise overview of heterocyclic active compounds and families and their main applications in medicine. We shall focus on those suitable for cancer therapy while simultaneously addressing main biochemical modes of action, biological targets, structure-activity relationships as well as intrinsic limitation issues in the use of these compounds. Finally, considering the advent of nanotechnology for effective selective targeting of drugs, we shall discuss fundamental aspects and considerations on nanovectorization of such compounds that may improve pharmacokinetic/pharmacodynamic properties of heterocycles.

Chalcone based azacarboline analogues as novel antitubulin agents: design, synthesis, biological evaluation and molecular modelling studies

The present study involves the design of a series of 3-aryl-9-acetyl-pyridazino[3,4-b]indoles as constrained chalcone analogues. A retrosynthetic route was proposed for the synthesis of target compounds. All the synthesized compounds were evaluated for in-vitro cytotoxicity against THP-1, COLO-205, HCT-116 and A-549 human cancer cell lines. The results indicated that 2a, 3a, 5a and 6a possessed significant cytotoxic potential with an IC50 value ranging from 1.13 to 5.76 μM. Structure activity relationship revealed that the nature of both Ring A and Ring B influences the activity. Substitution of methoxy groups on the phenyl ring (Ring A) and unsubstituted phenyl ring (Ring B) were found to be the preferred structural features. The most potent compound 2a was further tested for tubulin inhibition. Compound 2a was found to significantly inhibit the tubulin polymerization (IC50 value - 2.41 μM against THP-1). Compound 2a also caused disruption of microtubule assembly as evidenced by Immunoflourescence technique. The significant cytotoxicity and tubulin inhibition by 2a was rationalized by molecular modelling studies. The most potent structure was docked at colchicine binding site (PDB ID-1SA0) and was found to be stabilized in the cavity via various hydrophobic and hydrogen bonding interactions.