Synthesis of substituted phenanthrene-9-benzimidazole conjugates: Cytotoxicity evaluation and apoptosis inducing studies

A Critical Review on Therapeutic Potential of Benzimidazole Derivatives: A Privileged Scaffold

Benzimidazole nucleus is a predominant heterocycle displaying a wide spectrum of pharmacological activities. The privileged nature of the benzimidazole scaffold has been revealed by its presence in most small molecule drugs and in its ability to bind multiple receptors with high affinity. A literature review of the scaffold reveals several instances where structural modifications of the benzimidazole core have resulted in high-affinity lead compounds against a variety of biological targets. Hence, this structural moiety offers opportunities to discover novel, better, safe and highly potent biological agents. The goal of the present review is to compile the medicinal properties of benzimidazole derivatives with a focus on SAR (Structure-Activity Relationships).

Triazolo-linked benzimidazoles as tubulin polymerization inhibitors and DNA intercalators: Design, synthesis, cytotoxicity, and docking studies

A simple "click" protocol was employed in the quest of synthesizing 1,2,3-triazole-linked benzimidazoles as promising anticancer agents on various human cancer cell lines such as A549, HCT116, SK-Mel-28, HT-29, and MCF-7. Compound 12j demonstrated significant cytotoxic potential towards SK-Mel-28 cancer cells (IC₅₀ : 4.17 ± 0.09 µM) and displayed no cytotoxicity (IC₅₀ : > 100 µM) against normal human BEAS-2B cells inferring its safety towards normal healthy cells. Further to comprehend the underlying apoptosis mechanisms, AO/EB, dichlorodihydrofluorescein diacetate (DCFDA), and 4',6-diamidino-2-phenylindole (DAPI) staining were performed, which revealed the nuclear and morphological alterations. Compound 12j displayed impairment in cellular migration and inhibited colony formation. The annexin V binding assay and JC-1 were implemented to evaluate the scope of apoptosis and the loss of the mitochondrial transmembrane potential in SK-Mel-28 cells. Cell-cycle analysis revealed that compound 12j arrested the cells at the G2/M phase in a dose-dependent manner. Target-based assays established the inhibition of tubulin polymerization by 12j at an IC₅₀ value of 5.65  ± 0.05 μM and its effective binding with circulating tumor DNA as a DNA intercalator. The detailed binding interactions of 12j with tubulin and DNA were examined by docking studies on PDB ID: 3E22 and DNA hexamer (PDB ID: 1NAB), respectively.

DNA Intercalators as Anticancer Agents

Cancer is one of the most prevailing disease conditions which occurs due to uncontrolled cell division either due to natural mutation to the genes or due to changes induced by physical, chemical, or biological carcinogens. According to WHO, it is the second leading cause of death worldwide and has reported 10 million deaths in 2020. Hence there arises the need for better chemotherapies and DNA intercalators are one such emerging therapy for cancer. DNA intercalating agents reversibly intercalate with the double-helical structure of DNA by interacting with adjacent base pairs and disrupting the structure of DNA and thereby causing cell death. Here we discuss the different classes of organo-intercalators used in cancer therapy describing their anticancer and intercalation ability by different methods along with their structure-activity relationship and mechanism of action.

Expedition of sulfur-containing heterocyclic derivatives as cytotoxic agents in medicinal chemistry: A decade update

This review article proposes a comprehensive report of the design strategies engaged in the development of various sulfur-bearing cytotoxic agents. The outcomes of various studies depict that the sulfur heterocyclic framework is a fundamental structure in diverse synthetic analogs representing a myriad scope of therapeutic activities. A number of five-, six- and seven-membered sulfur-containing heterocyclic scaffolds, such as thiazoles, thiadiazoles, thiazolidinediones, thiophenes, thiopyrans, benzothiazoles, benzothiophenes, thienopyrimidines, simple and modified phenothiazines, and thiazepines have been discussed. The subsequent studies of the derivatives unveiled their cytotoxic effects through multiple mechanisms (viz. inhibition of tyrosine kinases, topoisomerase I and II, tubulin, COX, DNA synthesis, and PI3K/Akt and Raf/MEK/ERK signaling pathways), and several others. Thus, our concise illustration explains the design strategy and anticancer potential of these five- and six-membered sulfur-containing heterocyclic molecules along with a brief outline on seven-membered sulfur heterocycles. The thorough assessment of antiproliferative activities with the reference drug allows a proficient assessment of the structure-activity relationships (SARs) of the diversely synthesized molecules of the series.

Synthesis and in Vitro Cytotoxicity Evaluation of Phenanthrene Linked 2,4- Thiazolidinediones as Potential Anticancer Agents

OBJECTIVE

To synthesize a series of phenanthrene-thiazolidinedione hybrids and explore their cytotoxic potential against human cancer cell lines of A-549 (lung cancer), HCT-116 and HT-29 (colon cancer), MDA MB-231 (triple-negative breast cancer), BT-474 (breast cancer) and (mouse melanoma) B16F10 cells.

METHODS

A new series of phenanthrene-thiazolidinedione hybrids was synthesized via Knoevenagel condensation of phenanthrene-9-carbaldehyde and N-alkylated thiazolidinediones. The cytotoxicity (IC₅₀) of the synthesized compounds was determined by MTT assay. Apoptotic assays like (AO/EB) and DAPI staining, cell cycle analysis, JC-1 staining and Annexin V binding assay studies were performed for the most active compound (Z)- 3-(4-bromobenzyl)-5-((2,3,6,7-tetramethoxyphenanthren-9-yl)methylene)thiazolidine-2,4-dione (17b). Molecular docking, dynamics and evaluation of pharmacokinetic (ADME/T) properties were also carried out by using Schrödinger.

RESULTS AND DISCUSSION

From the series of tested compounds, 17b unveiled promising cytotoxic action with an IC₅₀ value of 0.985±0.02μM on HCT-116 human colon cancer cells. The treatment of HCT-116 cells with 17b demonstrated distinctive apoptotic morphology like shrinkage of cells, horseshoe-shaped nuclei formation and chromatin condensation. The flow-cytometry analysis revealed the G0/G1 phase cell cycle arrest in a dosedependent fashion. The AO/EB, DAPI, DCFDA, Annexin-V and JC-1 staining studies were performed in order to determine the effect of the compound on cell viability. Computational studies were performed by using Schrödinger to determine the stability of the ligand with the DNA.

CONCLUSION

The current study provides an insight into developing a series of phenanthrene thiazolidinedione derivatives as potential DNA interactive agents which might aid in colon cancer therapy.

Recent advancements on Benzimidazole: A versatile scaffold in medicinal chemistry

Benzimidazole is nitrogen containing fused heterocycle which has been extensively explored in medicinal chemistry. Benzimidizole nucleus has been found to possess various biological activities such as anticancer, antimicrobial, anti-inflammatory, antiviral, antitubercular and antidiabetic. A number of benzimidazoles such as bendamustine, pantoprazole have been approved for the treatment of various illnesses whereas galeterone and GSK461364 are in clinical trials. The present review article gives an overview about the different biological activities exhibited by the benzimidazole derivatives as well as different methods used for the synthesis of benzimidazole derivatives for the past ten years.

Anticancer potential of spirocompounds in medicinal chemistry: A pentennial expedition

Spirocompounds constitute an important class of organic frameworks enveloping numerous pharmacological activities, among them, the promising anticancer potential of spirocompounds have enthused medicinal chemists to explore new spiro derivatives with significantly improved pharmacodynamic and pharmacokinetic profile along with their mechanism of action. The current review intends to provide a sketch of the anticancer activity of various spirocompounds like spirooxindole, spiroisoxazole, spiroindole etc, from the past five years unfolding various aspects of pharmacological activities and their structure-activity relationships (SARs). This literature analysis may provide future direction for the efficient design of novel spiromolecules with enhanced safety and efficacy.

Recent Progress of Benzimidazole Hybrids for Anticancer Potential

This review presents the detailed account of factors leading to cancer and design strategy for the synthesis of benzimidazole derivatives as anticancer agents. The recent survey for cancer treatment in Cancer facts and figures 2017 American Chemical Society has shown progressive development in fighting cancer. Researchers all over the world in both developed and developing countries are in a continuous effort to tackle this serious concern. Benzimidazole and its derivatives showed a broad range of biological activities due to their resemblance with naturally occurring nitrogenous base i.e. purine. The review discussed benzimidazole derivatives showing anticancer properties through a different mechanism viz. intercalation, alkylating agents, topoisomerases, DHFR enzymes, and tubulin inhibitors. Benzimidazole derivatives act through a different mechanism and the substituents reported from the earlier and recent research articles are prerequisites for the synthesis of targeted based benzimidazole derivatives as anticancer agents. The review focuses on an easy comparison of the substituent essential for potency and selectivity through SAR presented in figures. This will further provide a better outlook or fulfills the challenges faced in the development of novel benzimidazole derivatives as anticancer.

Synthesis and biological evaluation of substituted N-(2-(1H-benzo[d]imidazol-2-yl)phenyl)cinnamides as tubulin polymerization inhibitors

A new series of N-(2-(1H-benzo[d]imidazol-2-yl)phenyl) cinnamides was prepared and evaluated for their in vitro cytotoxic activity using various cancer cell lines viz. A549 (human non-small cell lung cancer), MDA-MB-231 (human triple negative breast cancer), B16-F10 (mouse melanoma), BT-474 (human breast cancer), and 4 T1 (mouse triple negative breast cancer). In the series of tested compounds, 12h showed potent cytotoxic activity against non-small cell lung cancer cell line with IC₅₀ value of 0.29 ± 0.02 µM. The cytoxicity of most potent compound 12h was also tested on NRK-52E (normal rat kidney epithelial cell line) and showed less cytotoxicity compared to cancer cells. Tubulin polymerization assay indicated that the compound 12h was able to impede the cell division by inhibiting tubulin polymerization. Moreover, molecular docking study also suggested the binding of 12h at the colchicine-binding site of the tubulin protein. Cell cycle analysis revealed that the compound 12h arrests G2/M phase. In addition, 12h induced apoptosis in A549 cell lines was evaluated by various staining studies like acridine orange, DAPI, analysis of mitochondrial membrane potential, annexin V-FITC, and DCFDA assays.

Antiviral Activity of Chitosan Nanoparticles Encapsulating Curcumin Against Hepatitis C Virus Genotype 4a in Human Hepatoma Cell Lines

Purpose

Current direct-acting antiviral agents for treatment of hepatitis C virus genotype 4a (HCV-4a) have been reported to cause adverse effects, and therefore less toxic antivirals are needed. This study investigated the role of curcumin chitosan (CuCs) nanocomposite as a potential anti-HCV-4a agent in human hepatoma cells Huh7.

Methods

Docking of curcumin and CuCs nanocomposite and binding energy calculations were carried out. Chitosan nanoparticles (CsNPs) and CuCs nanocomposite were prepared with an ionic gelation method and characterized with TEM, zeta size and potential, and HPLC to calculate encapsulation efficiency. Cytotoxicity studies were performed on Huh7 cells using MTT assay and confirmed with cellular and molecular assays. Anti-HCV-4a activity was determined using real-time PCR and Western blot.

Results

The strength of binding interactions between protein ligand complexes gave scores with NS3 protease, NS5A polymerase, and NS5B polymerase of -124.91, -159.02, and -129.16, for curcumin respectively, and -68.51, -54.52, and -157.63 for CuCs nanocomposite, respectively. CuCs nanocomposite was prepared at sizes 29-39.5 nm and charges of 33 mV. HPLC detected 4% of curcumin encapsulated into CsNPs. IC50 was 8 µg/mL for curcumin and 25 µg/mL for the nanocomposite on Huh7 but was 25.8 µg/mL and 34 µg/mL on WISH cells. CsNPs had no cytotoxic effect on tested cell lines. Apoptotic genes' expression revealed the caspase-dependent pathway mechanism. CsNPs and CuCs nanocomposite demonstrated 100% inhibition of viral entry and replication, which was confirmed with HCV core protein expression.

Conclusion

CuCs nanocomposite inhibited HCV-4a entry and replication compared to curcumin alone, suggesting its potential role as an effective therapeutic agent.

Synthesis and Biological Evaluation of Novel Heterocyclic Imines Linked Coumarin- Thiazole Hybrids as Anticancer Agents

Background:

Human Galectin-1, a protein of lectin family showing affinity towards β-galactosides has emerged as a critical regulator of tumor progression and metastasis, by modulating diverse biological events including homotypic cell aggregation, migration, apoptosis, angiogenesis and immune escape. Therefore, galectin-1 inhibitors might represent novel therapeutic agents for cancer.

Methods:

A new series of heterocyclic imines linked coumarin-thiazole hybrids (6a-6r) was synthesized and evaluated for its cytotoxic potential against a panel of six human cancer cell lines namely, lung (A549), prostate (DU-145), breast (MCF-7 & MDA-MB-231), colon (HCT-15 & HT-29) using MTT assay. Characteristic apoptotic assays like DAPI staining, cell cycle, annexin V and Mitochondrial membrane potential studies were performed for the most active compound. Furthermore, Gal-1 inhibition was confirmed by ELISA and fluorescence spectroscopy.

Results:

Among all, compound 6g 3-(2-(2-(pyridin-2-ylmethylene) hydrazineyl) thiazol-4-yl)-2H-chromen-2- one exhibited promising growth inhibition against HCT-15 colorectal cancer cells with an IC50 value of 1.28 ± 0.14 µM. The characteristic apoptotic morphological features like chromatin condensation, membrane blebbing and apoptotic body formation were clearly observed with compound 6g on HCT-15 cells using DAPI staining studies. Further, annexin V-FITC/PI assay confirmed effective early apoptosis induction by treatment with compound 6g. Loss of mitochondrial membrane potential and enhanced ROS generation were confirmed with JC-1 and DCFDA staining method, respectively by treatment with compound 6g, suggesting a possible mechanism for inducing apoptosis. Moreover, flow cytometric analysis revealed that compound 6g blocked G0/G1 phase of the cell cycle in a dose-dependent manner. Compound 6g effectively reduced the levels of Gal-1 protein in a dose-dependent manner. The binding constant (Ka) of 6g with Gal-1 was calculated from the intercept value which was observed as 1.9 x 107 M-1 by Fluorescence spectroscopy. Molecular docking studies showed strong interactions of compound 6g with Gal-1 protein.

Conclusion:

Our studies demonstrate the anticancer potential and Gal-1 inhibition of heterocyclic imines linked coumarin-thiazole hybrids.

Synthesis of enamino-2-oxindoles via conjugate addition between α-azido ketones and 3-alkenyl oxindoles: Cytotoxicity evaluation and apoptosis inducing studies

A facile method for the construction of double bond between 3-ylidene oxindoles and α-azido ketones has been successfully accomplished with a mild base. This method features azido reduction with concomitant double bond formation to provide the new class of bioactive enamino-2-oxindoles. These new compounds were screened for their in vitro cytotoxic potential on selected human cancer cell lines such as colon, lung, breast, and cervical cancer cells. Among them, representative compounds 3a, 3h, 3k, 3p, 3w and 3x showed notable cytotoxicity profile with IC₅₀ values ranging from 1.40 ± 0.10 to 28.7 ± 0.36 µM. Compound 3k displayed most potent cytotoxicity against lung cancer (NCI-H460) cells with an IC₅₀ value of 1.40 ± 0.10 µM. 3k also arrested the G2/M phase of the cell cycle and induced distinctive apoptotic features on lung cancer cells. The apoptosis induction is supported by various cellular assays such as AO/EB, DAPI, and DCFDA staining studies including clonogenic assay. Extent of apoptosis was also analyzed by Annexin binding and JC-1 staining. Moreover, this method is amenable for the generation of a library of new class of stable bioactive enamino-2-oxindoles.

A novel series of pyrazole-platinum(II) complexes as potential anti-cancer agents that induce cell cycle arrest and apoptosis in breast cancer cells

Six novel compounds of platinum(II) with pyrazole derivatives PtPz1-PtPz6 were synthesised and characterised (PtPz1 - [Pt₂N-hydroksymethyl-3,5-dimethylpyrazole₄(berenil)₂]Cl₄; PtPz2 - [Pt₂3,5-dimethylpyrazole₄(berenil)₂]Cl₄; PtPz3 - [Pt₂3,4-dimethylpyrazole₄(berenil)₂]Cl₄; PtPz4 - [Pt₂pyrazole₄(berenil)₂]Cl₄; PtPz5- [Pt₂5-methylpyrazole₄(berenil)₂]Cl₄; PtPz6 - [Pt₂N-ethylpyrazole₄(berenil)₂]Cl₄). The cytotoxic activity of these complexes against MCF-7 and MDA-MB-231 breast cancer cell lines was determined using the MTT assay. Evaluation of apoptosis induction was done with the Annexin V-fluorescein isothiocyanate/propidium iodide assay. In addition, using a flow cytometer, we determined the influence of test compounds on the cell cycle and caspase-3, -8, and -9 activity. The obtained results of caspase activity were confirmed by cell imaging. Moreover, using the flow cytometer, the effects of the test compounds on mitochondrial potential change were assessed. The test results showed that novel pyrazole-platinum(II) complexes exhibited stronger anti-proliferative activity against two breast cancer cell lines than reference cisplatin. Compounds PtPz1, PtPz2, and PtPz3 with methyl substituents at the pyrazole ring showed stronger activity than pyrazole or ethylpyrazole containing complexes. Studies have shown that inhibition of cell survival occurs by arresting the G1 cell cycle and inducing apoptosis. Our analysis associated with the response of MCF-7 and MDA-MB-231 cells to treatment with PtPz1-PtPz6 showed that it leads the cells through the external and intrinsic (mitochondrial) apoptotic pathway via indirect DNA damage.

Synthesis and characterization of novel classes of PDE10A inhibitors - 1H-1,3-benzodiazoles and imidazo[1,2-a]pyrimidines

New compounds containing [1,2,4]triazolo [1,5-a]pyridine (I), pyrazolo [1,5-a]pyridine (II), 1H-1,3-benzodiazole (III) and imidazo [1,2-a]pyrimidine (IV) backbones were designed and synthesized for PDE10A interaction. Among these compounds, 1H-1,3-benzodiazoles and imidazo [1,2-a]pyrimidines showed the highest affinity for PDE10A enzyme as well as good metabolic stability. Both classes of compounds were identified as selective and potent PDE10A enzyme inhibitors.

Synthesis and in vitro cytotoxicity evaluation of β-carboline-linked 2,4-thiazolidinedione hybrids: potential DNA intercalation and apoptosis-inducing studies

A series of β-carboline-linked 2,4-thiazolidinedione hybrids was synthesized and studied for their DNA affinities and cytotoxicities. The most potent compound was 19e with IC₅₀ of 0.97 ± 0.13 μM.