A rapid and versatile synthesis of novel pyrimido[5,4-b]carbazoles

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.

New Achievements for the Treatment of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) constitutes a heterogeneous group of malignancies that are often aggressive and associated with a poor prognosis. The development of new TNBC treatment strategies has become an urgent clinical need. Diagnosis and subtyping of TNBC are essential to establish alternative treatments and targeted therapies for every TNBC patient. Chemotherapy, particularly with anthracycline and taxanes, remains the backbone for medical management for both early and metastatic TNBC. More recently, immune checkpoint inhibitors and targeted therapy have revolutionized cancer treatment. Included in the different strategies studied for TNBC treatment is drug repurposing. Despite the numerous medications available, numerous studies in medicinal chemistry are still aimed at the synthesis of new compounds in order to find new antiproliferative agents capable of treating TNBC. Additionally, some supplemental micronutrients, nutraceuticals and functional foods can potentially reduce the risk of developing cancer or can retard the rate of growth and metastases of established malignant diseases. Finally, nanotechnology in medicine, termed nanomedicines, introduces nanoparticles of variable chemistry and architecture for cancer treatment. This review highlights the most recent studies in search of new therapies for the treatment of TNBC, along with nutraceuticals and repositioning of drugs.

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.

Carbazole Derivatives as Kinase-Targeting Inhibitors for Cancer Treatment

Protein Kinases (PKs) are a heterogeneous family of enzymes that modulate several biological pathways, including cell division, cytoskeletal rearrangement, differentiation and apoptosis. In particular, due to their crucial role during human tumorigenesis and cancer progression, PKs are ideal targets for the design and development of effective and low toxic chemotherapeutics and represent the second group of drug targets after G-protein-coupled receptors. Nowadays, several compounds have been claimed to be PKs inhibitors, and some of them, such as imatinib, erlotinib and gefitinib, have already been approved for clinical use, whereas more than 30 others are in various phases of clinical trials. Among them, some natural or synthetic carbazole-based molecules represent promising PKs inhibitors due to their capability to interfere with PK activity by different mechanisms of action including the ability to act as DNA intercalating agents, interfere with the activity of enzymes involved in DNA duplication, such as topoisomerases and telomerases, and inhibit other proteins such as cyclindependent kinases or antagonize estrogen receptors. Thus, carbazoles can be considered a promising this class of compounds to be adopted in targeted therapy of different types of cancer.

Carbazole Derivatives as Antiviral Agents: An Overview

Keywords: carbazole; tetrahydrocarbazole; antiviral agents.

N-thioalkylcarbazoles derivatives as new anti-proliferative agents: synthesis, characterisation and molecular mechanism evaluation

Synthetic or natural carbazole derivatives constitute an interesting class of heterocycles, which showed several pharmaceutical properties and occupied a promising place as antitumour tools in preclinical studies. They target several cellular key-points, e.g. DNA and Topoisomerases I and II. The most studied representative, i.e. Ellipticine, was introduced in the treatment of metastatic breast cancer. However, because of the onset of dramatic side effects, its use was almost dismissed. Many efforts were made in order to design and synthesise new carbazole derivatives with good activity and reduced side effects. The major goal of the present study was to synthesise a series of new N-thioalkylcarbazole derivatives with anti-proliferative effects. Two compounds, 5a and 5c, possess an interesting anti-proliferative activity against breast and uterine cancer cell lines without affecting non-tumoural cell lines viability. The most active compound (5c) induces cancer cells death triggering the intrinsic apoptotic pathway by inhibition of Topoisomerase II.

Inhibition of Human Topoisomerase II by N,N,N-Trimethylethanammonium Iodide Alkylcarbazole Derivatives

Chemotherapy is used for the treatment of all stages of breast cancer, including the metastatic stage of the disease. Treatment regimens are generally tailored for each patient's particular situation. However, chemotherapeutic agents are the leading cause of serious drug-related adverse effects; moreover, drug resistance often occurs. In this study, we designed and synthesized a new series of N-alkylcarbazoles derived from ellipticine, an alkaloid with a carbazole skeleton initially used in the treatment of metastatic breast cancer and later dismissed because of poor aqueous solubility and severe side effects. After evaluating the binding modes of our class of newly synthesized compounds with human topoisomerase II (hTopo II), we performed hTopo II decatenation assays, identifying compound 4 f (2-(4-((3-chloro-9H-carbazol-9-yl)pentyl)piperazin-1-yl)-N,N,N-trimethylethanammonium iodide) as a good inhibitor. Moreover, 4 f and 4 g (2-(4-((3-chloro-9H-carbazol-9-yl)hexyl)piperazin-1-yl)-N,N,N-trimethylethanammonium iodide) showed a good anti-proliferative activity toward breast cancer cells, causing apoptosis by activation of the caspase pathway. Interestingly, the activity of these two compounds on triple-negative MDA-MB-231 cells, which tend to be highly metastatic and aggressive, is strictly connected to the observed inhibition of hTopo II.

Design, synthesis and biological evaluation of new carbazole derivatives as anti-cancer and anti-migratory agents

Based on the efficacy of EHop-016 as an inhibitor of migration and Rac1 activation, a new series of carbazole derivatives has been synthesized. Cytotoxic and anti-migratory effects of these compounds were evaluated in MCF-7 and MDA-MB-231 breast cancer cell lines. Preliminary investigations of their anticancer activity demonstrated that several compounds have moderate antiproliferative effects on cancer cell lines with GI50 values in the range of 13-50 µM. Furthermore, compounds 3b and 11b inhibit migration activity of metastatic cell line MDA-MB-231 by 32% and 34%, respectively. Compound 11b was shown to inhibit activation of the Rho GTPase Rac1 by 55% at 250 nM in both MDA-MB-231 and MDA-MB-435 cell lines. Compared with the IC50 of Rac1 inhibition by lead compound EHop-016 of 1.1 µM, compound 11b demonstrates 4X improved in vitro efficacy.

Assessment of antioxidant, antitumor and pro-apoptotic effects of Salvia fruticosa Mill. subsp. thomasii (Lacaita) Brullo, Guglielmo, Pavone & Terrasi (Lamiaceae)

The aim of the present study was to investigate the in vitro antioxidant and antitumor effects of Salvia fruticosa Mill subsp. thomasii (Lacaita) Brullo, Guglielmo, Pavone & Terrasi (Lamiaceae). The aerial parts were extracted by maceration with methanol. This extract was partitioned with methanol and n-hexane. Luteolin, luteolin 7-O-glucoside, rutin and salvigenin were isolated from the methanol-soluble fraction. n-Hexane fraction showed viridiflorol, β-pinene, 1,8-cineole, as main components. The methanol-soluble fraction exerted antitumor activity against human breast cancer (MCF-7 and MDA-MB-231) and human colorectal carcinoma (RKO and Caco-2) cells. TUNEL test revealed that S. fruticosa subsp. thomasii leads to cells death by apoptosis, with low cytotoxic effects on non-tumoral 3T3-L1 cells. Moreover, it exerted the highest protection of lipid peroxidation and reduced the oxidative stress induced by menadione treatment in 3T3-L1 murine fibroblasts. S. fruticosa subsp. thomasii bioactivity could promote its use not only as food but also in nutraceutical/pharmaceutical industries.

Multifaceted properties of 1,4-dimethylcarbazoles: Focus on trimethoxybenzamide and trimethoxyphenylurea derivatives as novel human topoisomerase II inhibitors

Natural or synthetic carbazole derivatives have recently attracted the attention of the scientific world because of their multiple biological activity, leading to an increase of designed, synthesized and studied analogues. In this paper, four 1,4-dimethylcarbazole derivatives, analogues of Ellipticine, have been investigated for their ability to block cancer cells growth, with low effects on the proliferation of normal cells. DNA topoisomerases inhibition assays, docking simulations, stability studies and effects on a membrane model are reported. Particularly, compounds 2 and 3 have been found thermally stable and able to inhibit, strongly and selectively, the human DNA topoisomerase II. These properties confer a good and broad antitumoral activity in vitro, with very low cytotoxic effect on the proliferation of normal cell lines and without damaging, in contrast with Ellipticine, the cell membrane model. The presented outcomes set the most active compounds as good candidates for pre-clinical studies useful in cancer treatment.

3-(Dipropylamino)-5-hydroxybenzofuro[2,3-f]quinazolin-1(2H)-one (DPA-HBFQ-1) plays an inhibitory role on breast cancer cell growth and progression

A series of unknown 3-(alkyl(dialkyl)amino)benzofuro[2,3-f]quinazolin-1(2H)-ones 4-17 has been synthesized as new ellipticine analogs, in which the carbazole moiety and the pyridine ring were replaced by a dibenzofuran residue and a pyrimidine ring, respectively. The synthesis of these benzofuroquinazolinones 4-17 was performed in a simple one-pot reaction using 3-aminodibenzofuran or its 2-methoxy derivative, as starting materials. From 3-(dipropylamino)-5-methoxybenzofuro[2,3-f] quinazolin-1(2H)-one (13), we prepared 3-(dipropylamino)-5-hydroxybenzofuro[2,3-f]quinazolin-1(2H)-one (18), referred to as DPA-HBFQ-1. The cytotoxic activities of all the synthesized compounds, tested in different human breast cancer cell lines, revealed that DPA-HBFQ-1 was the most active compound. In particular, the latter was able to inhibit anchorage-dependent and -independent cell growth and to induce apoptosis in estrogen receptor alpha (ERα)-positive and -negative breast cancer cells. It did not affect proliferation and apoptotic responses in MCF-10A normal breast epithelial cells. The observed effects have been ascribed to an enhanced p21(Cip1/WAF1) expression in a p53-dependent manner of tumor suppressor and to a selective inhibition of human topoisomerase II. In addition, DPA-HBFQ-1 exerted growth inhibitory effects also in other cancer cell lines, even though with a lower cytotoxic activity. Our results indicate DPA-HBFQ-1 as a good candidate to be useful as cancer therapeutic agent, particularly for breast cancer.

Monitoring the Competence of a New Keto-tetrahydrocarbazole Based Fluorosensor Under Homogeneous, Micro-Heterogeneous and Serum Albumin Environments

We present here a detailed photophysical study of a recently synthesised fluorophore 8-methyl-8,9-dihydro-5H-[1,3]dioxolo[4,5-b]carbazol-6(7H)-one. This is a synthetic precursor of bio-active carbazole skeleton Clausenalene. Spectroscopic investigation of the fluorophore has been carried out in different protic and aprotic solvents, as well as in binary solvent mixtures, using absorption, steady-state and time-resolved fluorescence techniques. This fluorophore is particularly responsive to the hydrogen bonding nature as well as polarity of the solvent molecules. When considered in micelles and β-cyclodextrin, this behaves as a reporter of its immediate microenvironment. Steady state and time resolved fluorometric and circular dichroism techniques have been used to explore the binding interaction of the fluorophore with transport proteins, bovine serum albumin and human serum albumin. The probable binding sites of the fluorophore in the proteinous environments have been evaluated from fluorescence resonance energy transfer study. Laser flash photolysis experiments also have been performed to observe the triplet excited state interaction between the fluorophore and albumin proteins.

N-alkyl carbazole derivatives as new tools for Alzheimer's disease: preliminary studies

Alzheimer's disease (AD) is a progressive and age-related neurodegenerative disorder affecting brain cells and is the most common form of "dementia", because of the cognitive detriment which takes place. Neuronal disruption represents its major feature, due to the cytosolic accumulation of amyloid β-peptide (Aβ) which leads to senile plaques formation and intracellular neurofibrillary tangles. Many studies have focused on the design and therapeutic use of new molecules able to inhibit Aβ aggregation. In this context, we evaluated the ability of two recently synthesized series of N-alkyl carbazole derivatives to increase the Aβ soluble forms, through molecular docking simulations and in vitro experiments. Our data evidenced that two carbazole derivatives, the most active, adopt distinct binding modes involving key residues for Aβ fibrillization. They exhibit a good interfering activity on Aβ aggregation in mouse (N2a) cells, stably expressing wild-type human amyloid precursor protein (APP) 695. These preliminary results are promising and we are confident that the N-alkyl carbazole derivatives may encourage next future studies needed for enlarging the knowledge about the AD disease approach.

Magnetic molecularly imprinted polymers (MMIPs) for carbazole derivative release in targeted cancer therapy

Magnetic Molecularly Imprinted Polymers (MMIPs) are synthesized with the aim to prepare novel devices for 9H-carbazole derivative sustained delivery in targeted cancer therapy.

Synthesis and evaluation of cytotoxic activities of new guanidines derived from carbazoles

Several new alkylguanidines derived from carbazole have been synthesized in a simple one-pot reaction starting from 3-aminocarbazole derivatives. The aminocarbazoles were reacted with ethoxycarbonylisothiocyanate, to give thiourea intermediates, followed by the addition of an alkylamine and HgCl2 to give ethoxycarbonylguanidine intermediates. The reaction mixture was then heated at 160 °C to give the N-(1,4-dimethyl-9H-carbazol-3-yl)-N'-alkylguanidines. The cytotoxic activity of all the synthesized guanidines was evaluated against different cell lines.

Catalyst-free synthesis of quinazolin-4-ones from (hetero)aryl-guanidines: application to the synthesis of pyrazolo[4,3-f]quinazolin-9-ones, a new family of DYRK1A inhibitors

A small library of heterocycle-fused quinazolin-4-ones was prepared and evaluated as kinase inhibitors. The key step of the two-step process involves the environmental friendly thermolysis of N-ethoxycarbonyl-N'-(hetero) arylguanidines at 130 °C in water. The cyclization is fully regioselective. The most active molecules, 7-(2-hydroxyethylamino)- and 7-(3-hydroxypropylamino)-pyrazolo[4,3-f]quinazolin-9-ones, inhibit DYRK1A and CLK1 at submicromolar concentrations, indicating the potential interest of this new heterocycle in drug design.

Copper-mediated domino synthesis of pyrimido[4,5-b]carbazolones via Ullmann N-arylation and aerobic oxidative C-H amidation

New pyrimido[4,5-b]carbazolone derivatives have been synthesized through cascade Ullmann N-arylation and aerobic oxidative C-H amidation reactions catalyzed by CuBr under air and ligand-free conditions.