Synthesis, structure-activity relationship studies and biological evaluation of novel 2,5-disubstituted indole derivatives as anticancer agents

Synthesis and Biological Evaluation of 1-(2-(6-Methoxynaphthalen-2-yl)-6-methylnicotinoyl)-4-Substituted Semicarbazides/Thiosemicarbazides as Anti-Tumor Nur77 Modulators

Nur77 is an orphan nuclear receptor that participates in the occurrence and development of a variety of tumors. Many agonists of Nur77 have been reported to have significant anticancer effects. Our previous studies have found that the introduction of bicyclic aromatic rings, such as naphthalyl and quinoline groups, into the N'-methylene position of indoles' Nur77 modulators can effectively improve the anti-tumor activity of the target compounds. Following our previous studies, a series of novel 1-(2-(6-methoxynaphthalen-2-yl)-6-methylnicotinoyl)-4-substituted semicarbazide/thiosemicarbazide derivatives 9a-9w were designed and synthesized in four steps from 6-methoxy-2-acetonaphthone and N-dimethylformamide dimethylacetal. All compounds were characterized by 1H-NMR, 13C-NMR and HRMS, and their anti-tumor activity on various cancer cell lines such as A549, HepG2, HGC-27, MCF-7 and HeLa are also evaluated. From the series of compounds, 9h exhibited the most potent anti-proliferative activity against several cancer cells. Colony formation and cell cycle experiments showed that compound 9h inhibited cell growth and arrested the cell cycle. Additionally, 9h leads to the cleavage of PARP. We initially explored the mechanism of 9h-induced apoptosis and found that compound 9h can upregulate Nur77 expression and triggered Nur77 nuclear export, indicating the occurrence of Nur77-mediated apoptosis. These results suggested that 9h may be a promising anti-tumor leading compound for the further research.

Synthesis and Antiproliferative Activity of New Thiosemicarboxamide Derivatives

To discover new anticancer agents, two series of thiosemicarboxamide derivatives were synthesized and evaluated for their antiproliferative activity against human cancer cells in vitro. Most target compounds (especially 3f, 3g, and 3h) exhibit potent antiproliferative activity against HeLa cells. Importantly, compound 3h, bearing a 4-methylphenyl substituent at N position of thiourea moiety, has significant and broad-spectrum inhibitory activities against cancer cells (HepG2, HeLa, MDA-MB231, A875, and H460 cells) with low IC₅₀ values (<5.0 μM) and shows low toxicity to normal LO2 and MRC-5 cells. Further studies show that compound 3h exerts high inhibitory activity in cancer cells by inducing the G2/M-phase arrest of cancer cells. Collectively, this study presents compound 3h as a new entity for the development of cell cycle arrest inducers for the treatment of cancer.

Design, synthesis, and biological evaluation of 5-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)-1H-Indole-2-Carbohydrazide derivatives: the methuosis inducer 12A as a Novel and selective anticancer agent

This study describes the synthesis and vacuole-inducing activity of 5-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)-1H-indole-2-carbohydrazide derivatives, including five potent derivatives 12c, 12 g, 12i, 12n, and 12A that exhibit excellent vacuole-inducing activity. Remarkably, 12A effectively induces methuosis in tested cancer cells but not human normal cells. In addition, 12A exhibits high pan-cytotoxicity against different cancer cell lines but is hardly toxic to normal cells. It is found that the 12A-induced vacuoles are derived from macropinosomes but not autophagosomes. The 12A-induced cytoplasmic vacuoles may originate from the endoplasmic reticulum (ER) and be accompanied by ER stress. The MAPK/JNK signalling pathway is involved in the 12A-induced methuotic cell death. Moreover, 12A exhibits significant inhibition of tumour growth in the MDA-MB-231 xenograft mouse model. The excellent potency and selectivity of 12A prompt us to select it as a good lead compound for further development of methuosis inducers and investigation of the molecular and cellular mechanisms underlying methuosis.

Synthesis and Biological Activity of 2-Arylidene-N-(quinolin-6-yl)hydrazine-1-carboxamides

A series of 2-arylidene-N-(quinolin-6-yl)hydrazine-1-carboxamides 5a–5o were synthesized and characterized. The synthesized compounds (5a–5o) were screened in vitro against three breast cancer cell lines: SKBR3, MDA-MB-231, and MCF-7 cancer cell lines by the MTT assay. According to MTT results, compounds 5k and 5l showed better antiproliferative activities over MCF-7 cell lines with IC50 values of 8.50 and 12.51 μM. Colony formation assay indicated 5k/5l treatment obviously inhibited the growth of MCF-7 cells and 5k/5l-induced cell cycle was arrested in the G2-M phase. Moreover, 5k/5l significantly increased the level of cleaved PARP and induced the apoptosis in MCF-7 cells. In addition, compared to Hela cells, MCF-7 cells were more sensitive to 5k/5l treatment.

Isolation and Antibacterial Activity of Indole Alkaloids from Pseudomonas aeruginosa UWI-1

In this study, we report the first isolation of three antibiotic indole alkaloid compounds from a Pseudomonad bacterium, Pseudomonas aeruginosa UWI-1. The bacterium was batch fermented in a modified Luria Broth medium and compounds were solvent extracted and isolated by bioassay-guided fractionation. The three compounds were identified as (1) tris(1H-indol-3-yl) methylium, (2) bis(indol-3-yl) phenylmethane, and (3) indolo (2, 1b) quinazoline-6, 12 dione. A combination of 1D and 2D NMR, high-resolution mass spectrometry data and comparison from related data from the literature was used to determine the chemical structures of the compounds. Compounds 1–3 were evaluated in vitro for their antimicrobial activities against a wide range of microorganisms using the broth microdilution technique. Compounds 1 and 2 displayed antibacterial activity against only Gram-positive pathogens, although 1 had significantly lower minimum inhibitory concentration (MIC) values than 2. Compound 3 displayed potent broad-spectrum antimicrobial activity against a range of Gram positive and negative bacteria. Several genes identified from the genome of P. aeruginosa UWI-1 were postulated to contribute to the biosynthesis of these compounds and we attempted to outline a possible route for bacterial synthesis. This study demonstrated the extended metabolic capability of Pseudomonas aeruginosa in synthesizing new chemotypes of bioactive compounds.

Role of Indole Scaffolds as Pharmacophores in the Development of Anti-Lung Cancer Agents

Lung cancer is the leading cause of death in men and women worldwide, affecting millions of people. Between the two types of lung cancers, non-small cell lung cancer (NSCLC) is more common than small cell lung cancer (SCLC). Besides surgery and radiotherapy, chemotherapy is the most important method of treatment for lung cancer. Indole scaffold is considered one of the most privileged scaffolds in heterocyclic chemistry. Indole may serve as an effective probe for the development of new drug candidates against challenging diseases, including lung cancer. In this review, we will focus on discussing the existing indole based pharmacophores in the clinical and pre-clinical stages of development against lung cancer, along with the synthesis of some of the selected anti-lung cancer drugs. Moreover, the basic mechanism of action underlying indole based anti-lung cancer treatment, such as protein kinase inhibition, histone deacetylase inhibition, DNA topoisomerase inhibition, and tubulin inhibition will also be discussed.

Recent advances in the pharmacological diversification of quinazoline/quinazolinone hybrids

Due to the pharmacological activities of quinazoline and quinazolinone scaffolds, it has aroused great interest in medicinal chemists for the development of new drugs or drug candidates. The pharmacological activities of quinazoline and its related scaffolds include anti-cancer, anti-microbial, anti-convulsant, and antihyperlipidaemia. Recently, molecular hybridization technology is used for the development of hybrid analogues with improved potency by combining two or more pharmacophores of bioactive scaffolds. The molecular hybridization of various biologically active pharmacophores with quinazoline derivatives resulted in lead compounds with multi-faceted biological activity wherein specific as well as multiple targets were involved. The present review summarizes the advances in lead compounds of quinazoline hybrids and their related heterocycles in medicinal chemistry. Moreover, the review also helps to intensify the drug development process by providing an understanding of the potential role of these hybridized pharmacophoric features in exhibiting various pharmacological activities.

Recent advances in quinazoline/quinazolinone hybrid heterocycles in medicinal chemistry and their pharmacological diversification.

Medicinal chemistry of indole derivatives: Current to future therapeutic prospectives

Indole is a versatile pharmacophore, a privileged scaffold and an outstanding heterocyclic compound with wide ranges of pharmacological activities due to different mechanisms of action. It is an superlative moiety in drug discovery with the sole property of resembling different structures of the protein. Plenty of research has been taking place in recent years to synthesize and explore the various therapeutic prospectives of this moiety. This review summarizes some of the recent effective chemical synthesis (2014-2018) for indole ring. This review also emphasized on the structure-activity relationship (SAR) to reveal the active pharmacophores of various indole analogues accountable for anticancer, anticonvulsant, antimicrobial, antitubercular, antimalarial, antiviral, antidiabetic and other miscellaneous activities which have been investigated in the last five years. The precise features with motives and framework of each research topic is introduced for helping the medicinal chemists to understand the perspective of the context in a better way. This review will definitely offer the platform for researchers to strategically design diverse novel indole derivatives having different promising pharmacological activities with reduced toxicity and side effects.

Synthesis, Biological Evaluation and Molecular Docking of Novel Indole-Aminoquinazoline Hybrids for Anticancer Properties

A series of indole-aminoquinazolines was prepared via amination of the 2-aryl-4-chloroquinazolines with the 7-amino-2-aryl-5-bromoindoles. It was then evaluated for cytotoxicity in vitro against human lung cancer (A549), epithelial colorectal adenocarcinoma (Caco-2), hepatocellular carcinoma (C3A), breast adenocarcinoma (MCF-7), and cervical cancer (HeLa) cells. A combination on the quinazoline and indole moieties of a 2-phenyl and 2-(4-fluorophenyl) rings in compound 4b; 2-(4-fluorophenyl) and 3-chlorophenyl rings in compound 4f; or the two 2-(4-fluorophenyl) rings in compound 4g, resulted in significant and moderate activity against the Caco-2 and C3A cell lines. The indole-aminoquinazoline hybrids compounds 4f and 4g induced apoptosis in Caco-2 and C3A cells, and were also found to exhibit moderate (IC₅₀ = 52.5 nM) and significant (IC₅₀ = 40.7 nM) inhibitory activity towards epidermal growth factor receptor (EGFR) against gefitinib (IC₅₀ = 38.9 nM). Molecular docking suggests that 4a–h could bind to the ATP region of EGFR like erlotinib.

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.

The emerging picture of CDK9/P-TEFb: more than 20 years of advances since PITALRE

CDK9 is a prominent member of the transcriptional CDKs subfamily, a group of kinases whose function is to control the primary steps of mRNA synthesis and processing by eukaryotic RNA polymerase II. As a cyclin-dependent kinase, CDK9 activation in vivo depends upon its association with T-type cyclins to assemble the positive transcription elongation factor (P-TEFb). Although CDK9/P-TEFb phosphorylates the C-terminal domain of RNAP II in the same positions targeted by CDK7 (TFIIH) and CDK8 (Mediator), the former does not participate in the transcription initiation, but rather plays a unique role by driving the polymerase to productive elongation. In addition to RNAP II CTD, the negative transcription elongation factors DSIF and NELF also represent major CDK9 substrates, whose phosphorylation is required to overcome the proximal pause of the polymerase. CDK9 is recruited to specific genes through proteins that interact with both P-TEFb and distinct elements in DNA, RNA or chromatin, where it modulates the activity of individual RNAP II transcription complexes. The regulation of CDK9 function is an intricate network that includes post-translational modifications (phosphorylation/dephosphorylation and acetylation/deacetylation of key residues) as well as the association of P-TEFb with various proteins that can stimulate or inhibit its kinase activity. Several cases of CDK9 deregulation have been linked to important human diseases, including various types of cancer and also AIDS (due to its essential role in HIV replication). Not only HIV, but also many other human viruses have been shown to depend strongly on CDK9 activity to be transcribed within host cells. This review summarizes the main advances made on CDK9/P-TEFb field in more than 20 years, introducing the structural, functional and genetic aspects that have been elucidated ever since.