Current status of carbazole hybrids as anticancer agents

Access to Piperazine-Fused Pyrrolocarbazoles Enabled by Acid-Catalyzed Stereoselective Hydroarylation of Ynamide-Indoles and Subsequent Diels-Alder Reactions/Aromatizations

Pyrrolocarbazole skeletons are well known to possess a variety of biological activities that might be therapeutically useful in the treatment of cancers. Herein, an acid-catalyzed stereoselective hydroarylation/Diels-Alder cycloaddition/aromatization of ynamide-indoles is described. We newly designed and synthesized a variety of piperazine-fused pyrrolocarbazole derivatives that could be further applied to the synthesis of potent Wee1 inhibitors.

Structure-activity relationship study of new carbazole sulfonamide derivatives as anticancer agents with dual-target mechanism

A series of novel carbazole sulfonamide derivatives were synthesized and evaluated for antiproliferative activity. Among them, compounds 7 and 15 showed strong potency (IC50 values of 0.81-31.19 nM) against five different cancer cells including multidrug-resistant MCF7/ADR cells. Compound 15 displayed a high cancer cell selectivity (IC50(L02)/average IC50: SI = 7.7). The l-valine prodrug 7a and the phosphate prodrug 15a exerted rohust in vivo antitumor efficacies and accepted safety prolifes. Further mechanism studies revealed that 7 and 15 directly bind to the colchicine site in tubulin to block tubulin polymerization, promote microtubule fragmentation at the cellular level, and induce apoptosis with G2/M cell cycle arrest. These compounds also inhibit HEMC-1 cells migration and vascular tube formation. Additionally, compound 7 displayed a selective inhibition of Topo I. Collectively, these studies suggest that 7 and 15 represents a promising new generation of tubulin inhibitors for cancer treatment.

Synthesis of Functionalized 4-Hydroxy Carbazoles and Carbazole Alkaloids via Ring Expansion of Indole Cyclopentanone

The exploration of a ring expansion reaction from indole cyclopentanone to generate a range of diversely functionalized 4-hydroxyl carbazole frameworks, representing the core structure of numerous carbazole alkaloids, has been conducted under mild reaction conditions. This approach exhibits broad functional group tolerance and moderate to good yields. The practical applicability of this strategy has been demonstrated through the concise syntheses of carbazomycins A, D, and G.

Potential of covalently linked tamoxifen hybrids for cancer treatment: recent update

Cancer is a complex disease and the second leading cause of death globally, and breast cancer is still a leading cause of cancer death in women. Tamoxifen is the most commonly used drug for breast cancer (ER-positive) treatment and chemoprevention, saving the lives of millions of patients every year. In addition, the tamoxifen template has been explored extensively for the development of selective estrogen receptor modulators (SERMs) applicable in breast cancer, osteoporosis, and postmenopausal symptom treatment. Numerous anticancer drugs, including tamoxifen, are in use, but the complexity and heterogeneous nature of cancer complicate the effect of conventional targeted drugs, leading to adverse reactions and resistance. One of the significant approaches to overcome these shortcomings is drug hybrids, generated by covalently linking two or more active pharmacophores. These drug hybrids are remarkably effective in acting on multiple drug targets with higher selectivity and specificity. In recent years, several tamoxifen hybrids have been discovered as potential candidates for cancer treatment. The review highlights the recent progress in developing anticancer hybrids, including organometallic, fluorescent, photocaged, and novel ligand-based tamoxifen hybrids. It also demonstrates the significance of merging various pharmacophores with tamoxifen to produce more potent, precise, and effective anticancer agents. The study offers valuable knowledge to researchers working on cancer research with the hope of enhancing drug potency and reducing drug toxicity to improve cancer patients' lives.

Perfluoroalkylation of Triarylamines by EDA Complexes and Ulterior Sensitized [6π]-Electrocyclization to Perfluoroalkylated Endo-Carbazoles. Mechanistic and Photophysical Studies

Blue LEDs-irradiation of a mixture of N,N,N',N'-tetramethylethylenediamine (TMEDA) and perfluoroalkyl iodides (RF-I) - Electron Donor Acceptor (EDA)-complex - in the presence of triphenylamines (TPAs) in an aqueous solvent mixture afforded mono-perfluoroalkylated triphenylamines (RF-TPA) in good yields. These RF-TPA were further subjected to acetone-sensitized [6π]-electrocyclization at 315 nm-irradiation affording exclusively perfluoroalkylated endo-carbazole derivatives (RF-CBz) in quantitative yields. Mechanistic studies and photophysical properties of products are studied.

Novel carbazolyl-thiazolyl-chromone and carbazolyl-thiazolyl-pyrazole hybrids: synthesis, cytotoxicity evaluation and molecular docking studies

A simple synthetic method was performed to design a novel series of polycyclic systems consisting of carbazole-thiazolidinone-chromone hybrids 4a-e and carbazole-thiazolidinone-pyrazole hybrids 5a-e in excellent yields. The methodology depended on the one-pot four-component reaction of 3-amino-9-ethylcarbazole, substituted isothiocyanates, ethyl bromoacetate and 6-methyl-3-formylchromone in ethanol under ultrasound waves at 50 °C to give the carbazole-thiazolidinone-chromone hybrids 4a-e. The latter isolated products were treated with hydrazine hydrate in ethanol under ultrasound waves at 50 °C affording the corresponding carbazole-thiazolidinone-pyrazole hybrids 5a-e. Spectral and analytical data confirmed the structures of all the synthesized compounds. The target compounds were screened for their in vitro anticancer activities against HCT116, PC3 and HepG2 cancer cell lines using the standard SRB method. Fortunately, both compounds 5dand5e were the most active against all cancer cell lines compared with doxorubicin and can be promising anticancer agents. Both bioactive products 5band5e were studied by the molecular docking to see how they bind with VEGFR-2 receptor. The results indicated that those compounds exhibited high affinities towards VEGFR-2 and established remarkably similar interactions to those of the powerful VEGFR-2-KDR.

Cascade hydroarylation/Diels-Alder cycloaddition of alkynylindoles with electron-deficient alkynes and alkenes

Herein, a novel cascade gold(I)-catalyzed hydroarylation of alkynylindoles and subsequent Diels-Alder cycloaddition with electron-deficient alkynes and alkenes is described. A variety of azepino-fused hydrocarbazoles and carbazoles were obtained in moderate to excellent yields. Key features of this methodology are low catalyst loadings, high regioselectivity, broad functional group tolerances, access to important heterocycles, and 100% atom economy.

Synthesis of benzo[a]carbazole derivatives via intramolecular cyclization using Brønsted acidic carbonaceous material as the catalyst

In this work, a new procedure for the synthesis of benzo[a]carbazole from 1,3-diketones, primary amines, phenylglyoxal monohydrate, and malononitrile employing a solid acidic catalyst has been developed. The multicomponent reaction provided 3-cyanoacetamide pyrrole as an intermediate and then the formation of benzo[a]carbazole via intramolecular ring closure. The reaction was carried out for 2 h at 240 °C, resulting in the desired product with 73% yield. Acidic sites on the solid acid catalyst, made from rice husk-derived amorphous carbon with a sulfonic acid core (AC-SO3H), provided the best activity. Acidic sites on the surface of the catalyst, including carboxylic, phenolic, and sulfonic acids, were 4.606 mmol g-1 of the total acidity. AC-SO3H demonstrated low cost, low toxicity, porosity, stability, and flexibility of tuning and reusability.

Proapoptotic effects of halogenated bis-phenylthiourea derivatives in cancer cells

New halogenated thiourea derivatives were synthesized via the reaction of substituted phenylisothiocyanates with aromatic amines. Their cytotoxic activity was examined in in vitro studies against solid tumors (SW480, SW620, PC3), a hematological malignance (K-562), and normal keratinocytes (HaCaT). Most of the compounds were more effective against SW480 (1a, 3a, 3b, 5j), K-562 (2b, 3a, 4a), or PC3 (5d) cells than cisplatin, with favorable selectivity. Their anticancer mechanisms were studied by Annexin V-fluorescein-5-isothiocyanate apoptosis, caspase-3/caspase-7 assessment, cell cycle analysis, interleukin-6 (IL-6) release inhibition, and reactive oxygen species (ROS) generation assay. Thioureas 1a, 2b, 3a, and 4a were the most potent activators of early apoptosis in K-562 cells, and substances 1a, 3b, 5j triggered late-apoptosis or necrosis in SW480 cells. This proapoptotic effect was proved by the significant increase of caspase-3/caspase-7 activation. Cell cycle analysis revealed that derivatives 1a, 3a, 5j increased the number of SW480 and K-562 cells in the sub-G1 and/or G0/G1 phases, and one evoked cycle arrest at the G2 phase. The most potent thioureas inhibited IL-6 cytokine secretion from PC3 cells and both colon cancer cell lines. Apoptosis-inducing compounds also increased ROS production in all tumor cell cultures, which may enhance their anticancer properties.

Design, synthesis, molecular docking and biological evaluation of new carbazole derivatives as anticancer, and antioxidant agents

BACKGROUND

The carbazole skeleton is an important structural motif occurring naturally or synthesized chemically and has antihistaminic, antioxidant, antitumor, antimicrobial, and anti-inflammatory activities.

OBJECTIVES

This study aimed to design and synthesize a novel series of carbazole derivatives and evaluate their antiproliferative and antioxidant activities.

METHODS

The synthesized compounds were characterized utilizing HRMS, ¹H-, and ¹³C_APT-NMR, and assessed for their anticancer, antifibrotic, and antioxidant effects utilizing reference biomedical procedures. In addition, the AutoDock Vina application was used to perform in-silico docking computations.

RESULTS

A series of carbazole derivatives were synthesized and characterized in the current study. Compounds 10 and 11 were found to have a stronger antiproliferative effect than compounds 2-5 against HepG2, HeLa, and MCF7 cancer cell lines with IC₅₀ values of 7.68, 10.09, and 6.44 µM, respectively. Moreover, compound 9 showed potent antiproliferative activity against HeLa cancer cell lines with an IC₅₀ value of 7.59 µM. However, except for compound 5, all of the synthesized compounds showed moderate antiproliferative activities against CaCo-2 with IC₅₀ values in the range of 43.7-187.23 µM. All of these values were compared with the positive control anticancer drug 5-Fluorouracil (5-FU). In addition, compound 9 showed the most potent anti-fibrotic compound, and the cellular viability of LX-2 was found 57.96% at 1 µM concentration in comparison with the positive control 5-FU. Moreover, 4 and 9 compounds showed potent antioxidant activities with IC₅₀ values of 1.05 ± 0.77 and 5.15 ± 1.01 µM, respectively.

CONCLUSION

Most of the synthesized carbazole derivatives showed promising antiproliferative, antioxidant, and antifibrotic biological effects, and further in-vivo investigations are needed to approve or disapprove these results.

Oral Delivery of Anti-Parasitic Agent-Loaded PLGA Nanoparticles: Enhanced Liver Targeting and Improved Therapeutic Effect on Hepatic Alveolar Echinococcosis

Background

Alveolar echinococcosis (AE) is a lethal parasitic disease caused by infection with the metacestode of the dog/fox tapeworm Echinococcus multilocularis, which primarily affects the liver. Although continued efforts have been made to find new drugs against this orphan and neglected disease, the current treatment options remain limited, with drug delivery considered a likely barrier for successful treatment.

Methods

Nanoparticles (NPs) have gained much attention in the field of drug delivery due to their potential to improve delivery efficiency and targetability. In this study, biocompatible PLGA nanoparticles encapsulating a novel carbazole aminoalcohol anti-AE agent (H1402) were prepared to promote the delivery of the parent drug to liver tissue for treating hepatic AE.

Results

H1402-loaded nanoparticles (H1402-NPs) had a uniform spherical shape and a mean particle size of 55 nm. Compound H1402 was efficiently encapsulated into PLGA NPs with a maximal encapsulation efficiency of 82.1% and drug loading content of 8.2%. An in vitro uptake assay demonstrated that H1402-NPs rapidly penetrated the in vitro cultured pre-cyst wall and extensively accumulated in the pre-cysts of E. multilocularis within only 1 h. The biodistribution profile of H1402-NPs determined through ex vivo fluorescence imaging revealed significantly enhanced liver distribution compared to unencapsulated H1402, which translated to improved therapeutic efficacy and reduced systemic toxicity (especially hepatotoxicity and cytotoxicity) in a hepatic AE murine model. Following a 30-day oral regimen (100 mg/kg/day), H1402-NPs significantly reduced the parasitic burden in both the parasite mass (liver and metacestode total weight, 8.8%) and average metacestode size (89.9%) compared to unmedicated infected mice (both p-values < 0.05); the treatment outcome was more effective than those of albendazole- and free H1402-treated individuals.

Conclusion

Our findings demonstrate the advantages of encapsulating H1402 into PLGA nanoparticles and highlight the potential of H1402-NPs as a promising liver-targeting therapeutic strategy for hepatic AE.

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.

Therapeutic significance of molecular hybrids for breast cancer research and treatment

Worldwide, breast cancer is still a leading cause of cancer death in women. Indeed, over the years, several anti-breast cancer drugs have been developed; however, the complex heterogeneous nature of breast cancer disease reduces the applicability of conventional targeted therapies with the upsurge in side effects and multi-drug resistance. Molecular hybrids generated by a combination of two or more active pharmacophores emerged as a promising approach in recent years for the design and synthesis of anti-breast cancer drugs. The hybrid anti-breast cancer molecules are well known for their several advantages compared to the parent moiety. These hybrid forms of anti-breast cancer molecules demonstrated remarkable effects in blocking different pathways contributing to the pathogenies of breast cancer and improved specificity. In addition, these hybrids are patient compliant with reduced side effects and multi-drug resistance. The literature revealed that molecular hybrids are applied to discover and develop novel hybrids for various complex diseases. This review article highlights the recent progress (∼2018-2022) in developing molecular hybrids, including linked, merged, and fused hybrids, as promising anti-breast cancer agents. Furthermore, their design principles, biological potential, and future perspective are discussed. The provided information will lead to the development of novel anti-breast cancer hybrids with excellent pharmacological profiles in the future.

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.

Characterization of Novel Derivatives of MBQ-167, an inhibitor of the GTP-binding proteins Rac/Cdc42

Rac and Cdc42, are homologous GTPases that regulate cell migration, invasion, and cell cycle progression; thus, representing key targets for metastasis therapy. We previously reported on the efficacy of MBQ-167, which blocks both Rac1 and Cdc42 in breast cancer cells and mouse models of metastasis. To identify compounds with increased activity, a panel of MBQ-167 derivatives was synthesized, maintaining its 9-ethyl-3-(1H-1,2,3-triazol-1-yl)-9H-carbazole core. Similar to MBQ-167, MBQ-168 and EHop-097, inhibit activation of Rac and Rac1B splice variant and breast cancer cell viability, and induce apoptosis. MBQ-167 and MBQ-168 inhibit Rac and Cdc42 by interfering with guanine nucleotide binding, and MBQ-168 is a more effective inhibitor of PAK (1,2,3) activation. EHop-097 acts via a different mechanism by inhibiting the interaction of the guanine nucleotide exchange factor (GEF) Vav with Rac. MBQ-168 and EHop-097 inhibit metastatic breast cancer cell migration, and MBQ-168 promotes loss of cancer cell polarity to result in disorganization of the actin cytoskeleton and detachment from the substratum. In lung cancer cells, MBQ-168 is more effective than MBQ-167 or EHop-097 at reducing ruffle formation in response to EGF. Comparable to MBQ-167, MBQ-168 significantly inhibits HER2+ tumor growth and metastasis to lung, liver, and spleen. Both MBQ-167 and MBQ-168 inhibit the cytochrome P450 (CYP) enzymes 3A4, 2C9, and 2C19. However, MBQ-168 is ~10X less potent than MBQ-167 at inhibiting CYP3A4, thus demonstrating its utility in relevant combination therapies. In conclusion, the MBQ-167 derivatives MBQ-168 and EHop-097 are additional promising anti metastatic cancer compounds with similar and distinct mechanisms.

Design, Synthesis and Anti-Tumor Activity Evaluation of Novel 3,4-(Methylenedioxy)cinnamic Acid Amide-Dithiocarbamate Derivatives

The fragments, 3,4-(methylenedioxy)cinnamic acid amide and dithiocarbamates, have received increasing attention because of their multiple pharmacological activities in recent years, especially in anti-tumor. We synthesized 17 novel 3,4-(methylenedioxy)cinnamic acid amide-dithiocarbamate derivatives based on the principle of pharmacophore assembly and discovered that compound 4a₇ displayed the most potent antiproliferative activity against HeLa cells with IC₅₀ value of 1.01 μM. Further mechanistic studies revealed that 4a₇ triggered apoptosis in HeLa cells via activating mitochondria-mediated intrinsic pathways and effectively inhibited colony formation. Also, 4a₇ had the ability to arrest cell cycle in the G2/M phase as well as to inhibit the migration in HeLa cells. More importantly, acute toxicity experiments showed that 4a₇ had good safety in vivo. All the results suggested that compound 4a₇ might serve as a promising lead compound that merited further attention in future anti-tumor drug discovery.

Photoinduced [6π]-Electrocyclic Reaction of Mono-, Di-, and Trisubstituted Triphenylamines in Acetonitrile. A Steady-State Investigation

Direct irradiation of mono-, di-, and trisubstituted triphenylamine derivatives in acetonitrile as solvent with light of 254 nm has been systematically investigated, revealing that the exo/endo carbazole derivatives were formed as the main photoproducts from modest to good yields for triphenylamines substituted with electron-donor and neutral substituents. The kinetic profiles of the photoreaction were also recorded, and the consumption rate constants (k) were measured. These kinetic parameters show dependence on the nature of the substituents, and linear Hammett correlations were carried out to showcase the substituent effect. On the other hand, the spectroscopic behavior of the electron-rich substituted triphenylamines has been analyzed, suggesting that the fluorescence emission spectra display a mirror image of the lower energy absorption bands, while for those amines bearing electron-acceptor groups the formation of charge-transfer complexes and their fluorescence emissions constitute the main deactivation pathway of the photoreaction.

Construction of carbazole-based unnatural amino acid scaffolds via Pd(II)-catalyzed C(sp3)-H functionalization

We report the synthesis of carbazole-based unnatural α-amino acid and non-α-amino acid derivatives via a Pd(II)-catalyzed bidentate directing group 8-aminoquinoline-aided β-C(sp³)-H activation/functionalization method. Various N-phthaloyl, DL-, L- and D-carboxamides derived from their corresponding α-amino acids, non-α-amino acids and aliphatic carboxamides were subjected to the β-C(sp³)-H functionalization with 3-iodocarbazoles in the presence of a Pd(II) catalyst to afford the corresponding carbazole moiety installed unnatural amino acid derivatives and aliphatic carboxamides. Carbazole motif-containing racemic (DL) and enantiopure (L and D) amino acid derivatives including phenylalanine, norvaline, leucine, norleucine and 2-aminooctanoic acid with anti-stereochemistry and various non-α-amino acid derivatives including GABA have been synthesized. Removal of the 8-aminoquinoline directing group, deprotection of the phthalimide moiety and the preparation of carbazole amino acid derivatives containing free amino- and carboxylate groups are shown. The carbazole motif is prevalent in alkaloids and biologically active molecules and functional materials. Thus, this work on the synthesis of carbazole-based unnatural amino acid derivatives would enrich the libraries of unnatural amino acid derivatives and carbazoles.