Metal complexes of β-carboline: Advances in anticancer therapeutics

Reversible Restrain and Release of the Dynamic Valence Isomerization in a Shape-shifting Bullvalene by Complex Formation

In search for structural features that enable the control of the valence isomerization of the fluxional bullvalene, a bullvalene-bis(harmane) conjugate is identified that acts as chelating ligand in complexes with metal ions. Spectrometric titrations show that this ligand forms 1 : 1 complexes with Ag+, Cu+, Cu2+, and Zn2+. Most importantly, detailed NMR-spectroscopic analysis at different temperatures reveals that the complexation with Ag+ strongly affects the dynamic isomerization of the bullvalene unit of the ligand such that only one predominant valence isomer is formed, even at 5 °C. Detailed 1H-NMR-spectroscopic studies disclose an increased barrier (~11 kJ mol-1) of the Cope rearrangement. Furthermore, the addition of hexacyclene displaces the Ag+ from the complex, so that the valence isomerization is accelerated and an equilibrium with two predominant isomers is formed. In turn, repeated addition of Ag+ regains the complex with the restrained isomerization of the bullvalene unit. This method to control the valence isomerism by straightforward chemical stimuli may be used to simplify structural analysis at elevated temperatures, i. e. a feature not available so far with bullvalenes, and it may be employed as functional element in dynamic supramolecular assemblies.

Anticancer mechanisms of β-carbolines

β-Carboline nucleus is therapeutically valuable in medicinal chemistry for the treatment of varied number of diseases, most importantly cancer. The potent and wide-ranging activity of β-carboline has established them as imperative pharmacological scaffolds especially in the cancer treatment. Numerous derivatives such as Tetrahydro β-carbolines, metal complexed β-carbolines, mono, di and tri substituted β-carbolines have been reported to possess dynamic anticancer activity. These different substituted β-carboline derivatives had shown different mechanism of action and plays important role in anticancer drug discovery and development. The review is an update of the chemistry of β-carbolines, both synthetic and natural origin acting through various targets against cancerous cells. In addition to this, studies of multitarget molecules designed by coupling β-carbolines along with other mechanisms for treatment of neoplasm are also summarized.

Anticancer Potential of β-Carboline Alkaloids: An Updated Mechanistic Overview

his comprehensive review is designed to evaluate the anticancer properties of β-carbolines derived from medicinal plants, with the ultimate goal of assessing their suitability and potential in cancer treatment, management, and prevention. An exhaustive literature survey was conducted on a wide array of β-carbolines including, but not limited to, harmaline, harmine, harmicine, harman, harmol, harmalol, pinoline, tetrahydroharmine, tryptoline, cordysinin C, cordysinin D, norharmane, and perlolyrine. Various analytical techniques were employed to identify and screen these compounds, followed by a detailed analysis of their anticancer mechanisms. Natural β-carbolines such as harmaline and harmine have shown promising inhibitory effects on the growth of cancer cells, as evidenced by multiple in vitro and in vivo studies. Synthetically derived β-carbolines also displayed noteworthy anticancer, neuroprotective, and cognitive-enhancing effects. The current body of research emphasizes the potential of β-carbolines as a unique source of bioactive compounds for cancer treatment. The diverse range of β-carbolines derived from medicinal plants can offer valuable insights into the development of new therapeutic strategies for cancer management and prevention.

Catechin from Anonna senegalensis is a Potential Inhibitor of Erectile Dysfunction: Implication for Its Use in Male Sexual Enhancement

Erectile dysfunction (ED) is a major challenge for men. The drugs for its treatment are associated with side effects. Hence, in phytomedicinal research, where Anonna senegalensis (A. senegalensis) is a candidate with abundant phytochemicals possessing various pharmacological properties, but the sex-enhancing phytochemical is elusive in the literature. This study aimed to understand the molecular interaction of its potent molecule mediating male sexual enhancement. A library of 69 compounds from A. senegalensis was docked against the ED-targeted proteins. Sildenafil citrate was used as the reference standard. Thereafter, the lead compound was screened for drug-likeness by applying the Lipinski rule of 5 (RO5), pharmacokinetic properties, and bioactivity using SwissADME and Molinspiration web servers, respectively. The results show catechin as the lead phytochemical compound with a stronger binding affinity for most of the proteins of ED. Also, catechin demonstrates good compliance with the RO5, great pharmacokinetic profiles, and could be said to be a polypharmacological molecule with good bioactivity scores. The research findings unravel the potential of catechin (a phytochemical belonging to the flavonoids class) from A. senegalensis leaf as a potential male sexual enhancement molecule via its high binding affinity for most erectile dysfunction-targeted proteins. They may require further toxicity and therapeutic evaluations in vivo.

Anticancer Activity and Mode of Action of Cu(II), Zn(II), and Mn(II) Complexes with 5-Chloro-2-N-(2-quinolylmethylene)aminophenol

Developing a new generation of anticancer metal-based drugs that can both kill tumor cells and inhibit cell migration is a promising strategy. Herein, we synthesized three Cu(II), Zn(II), and Mn(II) complexes derived from 5-chloro-2-N-(2-quinolylmethylene)aminophenol (C1-C3). Among these complexes, the Cu(II) complex (C1) showed significantly greater cytotoxicity toward lung cancer cell lines than cisplatin. C1 inhibited A549 cell metastasis and suppressed the growth of the A549 tumor in vivo. In addition, we confirmed the anticancer mechanism of C1 by triggering multiple mechanisms, including inducing mitochondrial apoptosis, acting on DNA, blocking cell cycle arrest, inducing cell senescence, and inducing DNA damage.

Addressing the gaps in homeostatic mechanisms of copper and copper dithiocarbamate complexes in cancer therapy: a shift from classical platinum-drug mechanisms

The platinum drug, cisplatin, is considered as among the most successful medications in cancer treatment. However, due to its inherent toxicity and resistance limitations, research into other metal-based non-platinum anticancer medications with diverse mechanisms of action remains an active field. In this regard, copper complexes feature among non-platinum compounds which have shown promising potential as effective anticancer drugs. Moreover, the interesting discovery that cancer cells can alter their copper homeostatic processes to develop resistance to platinum-based treatments leads to suggestions that some copper compounds can indeed re-sensitize cancer cells to these drugs. In this work, we review copper and copper complexes bearing dithiocarbamate ligands which have shown promising results as anticancer agents. Dithiocarbamate ligands act as effective ionophores to convey the complexes of interest into cells thereby influencing the metal homeostatic balance and inducing apoptosis through various mechanisms. We focus on copper homeostasis in mammalian cells and on our current understanding of copper dysregulation in cancer and recent therapeutic breakthroughs using copper coordination complexes as anticancer drugs. We also discuss the molecular foundation of the mechanisms underlying their anticancer action. The opportunities that exist in research for these compounds and their potential as anticancer agents, especially when coupled with ligands such as dithiocarbamates, are also reviewed.

Design, synthesis, and discovery of Eudistomin Y derivatives as lysosome-targeted antiproliferation agents

Eudistomin Y is a novel class of β-carbolines of marine origin with potential antiproliferation activity against MDA-MB-231 cells (triple-negative breast carcinoma). However, the subcellular target or the detailed mechanism against cancer cell proliferation has not yet been identified. In this study, based on its special structure, a novel series of Eudistomin Y fluorescent derivatives were designed and synthesized by enhancing the electron-donor effect of N-9 to endow it with fluorescent properties through N-alkylation. The structure-activity relationships against the proliferation of cancer cells were also analyzed. A quarter of Eudistomin Y derivatives showed much higher potency against cancer cell proliferation than the original Eudistomin Y₁. Fluorescent derivative H1k with robust antiproliferative activity could arrest MDA-MB-231 cells in the G2-M phase. The subcellular localization studies of the probes, including H1k, and Eudistomin Y1 were performed in MDA-MB-231 cells, and the co-localization and competitive inhibition assays revealed their lysosome-specific localization. Moreover, H1k could dose-dependently increase the autophagy signal and downregulate the expression of cyclin-dependent kinase (CDK1) and cyclin B1 which principally regulated the G2-M transition. Furthermore, the specific autophagy inhibitor 3-methyladenine significantly inhibited the H1k-triggered antiproliferation of cancer cells and the downregulation of CDK1 and cyclin B1. Overall, the lysosome is identified as the subcellular target of Eudistomin Y for the first time, and derivative H1k showed robust antiproliferative activity against MDA-MB-231 cells by decreasing Cyclin B1-CDK1 complex via a lysosome-dependent pathway.

3-(1,2,3-Triazol-4-yl)-β-Carbolines and 3-(1H-Tetrazol-5-yl)-β-Carbolines: Synthesis and Evaluation as Anticancer Agents

Herein, the synthesis and anticancer activity evaluation of a series of novel β-carbolines is reported. The reactivity of nitrosoalkenes towards indole was explored for the synthesis of novel tryptophan analogs where the carboxylic acid was replaced by a triazole moiety. This tryptamine was used in the synthesis of 3-(1,2,3-triazol-4-yl)-β-carbolines via Pictet-Spengler condensation followed by an oxidative step. A library of compounds, including the novel 3-(1,2,3-triazol-4-yl)-β-carbolines as well as methyl β-carboline-3-carboxylate and 3-tetrazolyl-β-carboline derivatives, was evaluated for their antiproliferative activity against colorectal cancer cell lines. The 3-(1H-tetrazol-5-yl)-β-carbolines stood out as the most active compounds, with values of half-maximal inhibitory concentration (IC₅₀) ranging from 3.3 µM to 9.6 µM against colorectal adenocarcinoma HCT116 and HT29 cell lines. The results also revealed a mechanism of action independent of the p53 pathway. Further studies with the 3-tetrazolyl-β-carboline derivative, which showed high selectivity for cancer cells, revealed IC₅₀ values below 8 μM against pancreatic adenocarcinoma PANC-1, melanoma A375, hepatocarcinoma HEPG2, and breast adenocarcinoma MCF-7 cell lines. Collectively, this work discloses the 3-tetrazolyl-β-carboline derivative as a promising anticancer agent worthy of being further explored in future works.

Epigenetic oncogenesis, biomarkers and emerging chemotherapeutics for breast cancer

Breast cancer remains one of the leading causes of cancer-related deaths globally and the most prominent among females, yet with limited effective therapeutic options. Most of the current medications are challenged by various factors including low efficacy, incessant resistance, immune evasion and frequent recurrence of the disease. Further understanding of the prognosis and identification of plausible therapeutic channels thus requires multimodal approaches. In this review, epigenetics studies of several pathways to BC oncogenesis via the inducement of oncogenic changes on relevant markers have been overviewed. Similarly, the counter-epigenetic mechanisms to reverse such changes as effective therapeutic strategies were surveyed. The epigenetic oncogenesis occurs through several pathways, notably, DNMT-mediated hypermethylation of DNA, dysregulated expression for ERα, HER2/ERBB and PR, histone modification, overexpression of transcription factors including the CDK9-cyclin T1 complex and suppression of tumour suppressor genes. Scientifically, the regulatory reversal of the mechanisms constitutes effective epigenetic approaches for mitigating BC initiation, progression and metastasis. These were exhibited at various experimental levels by classical chemotherapeutic agents including some repurposable drugs, endocrine inhibitors, monoclonal antibodies and miRNAs, natural products, metal complexes and nanoparticles. Dozens of the potential candidates are currently in clinical trials while others are still at preclinical experimental stages showing promising anti-BC efficacy. The review presents a model for a wider understanding of epigenetic oncogenic pathways to BC and reveals plausible channels for reversing the unpleasant changes through epigenetic modifications. It advances the science of therapeutic designs for ameliorating the global burden of BC upon further translational studies.

Structural modelling and in silico pharmacology of β-carboline alkaloids as potent 5-HT1A receptor antagonists and reuptake inhibitors

Serotonin (5-HT) antagonists and reuptake inhibitors (SARIs) are atypical antidepressants for managing major depressive disorder. They are oftentimes applied as adjuvants for ameliorating aftereffects of SSRI antidepressants including insomnia and sexual dysfunction. The few available candidates of this class including lorpiprazole and trazodone also display some daunting side effects, making a continuous search for improved alternatives essential. Natural β-carboline alkaloids (NβCs) are interestingly renowned with broad pharmacological spectrum against several neuropsychiatric disorders including depression. However, their potentials as SARIs remain underexplored. In this study, 982 NβCs retrieved from the Ambinter-Greenpharma (Amb) database were virtually screened for potent SARI alternatives using computational and biocheminformatics approaches: homology modelling of 5-HT1A receptor, Glide HTVS, SP and XP molecular docking, molecular dynamics (MD) simulation, ADMET and mutagenicity predictions. The homology receptor was validated as a good representative of human 5HT1A receptor using the RCSB structure validation and quality protocols. From the virtual screening against the 5-HT1A receptor, Amb ligands, Amb18709727 and Amb37857532 showed higher binding affinities by XP scores of -8.725 and -7.976 kcal/mol, and MMGBSA of -87.972 and -107.585 kcal/mol respectively compared to lorpiprazole, a reference SARI with XP score and MMGBSA of -6.512 and -62.788 kcal/mol respectively. They maintained ideal contacts with pharmacologically essential amino acid residues implicated in SARI mechanisms and expressed higher stability and compactness than lorpiprazole throughout the trajectories of 100 ns MD simulation. They also displayed interesting ADME, druggability, low toxicity and mutagenicity profiles, ideal for CNS drug prospects, thus, recommended as putative SARI candidates for further study.

A Green Synthesis of Carbene-Metal-Amides (CMAs) and Carboline-Derived CMAs with Potent in vitro and ex vivo Anticancer Activity

The modularity and ease of synthesis of carbene-metal-amide (CMA) complexes based on the coinage metals (Au, Ag, Cu) and N-heterocyclic carbenes (NHCs) as ancillary ligands pave the way for the expansion of their applications beyond photochemistry and catalysis. Herein, we further improve the synthesis of such compounds by circumventing the use of toxic organic solvents which were previously required for their purification, and we expand their scope to include complexes incorporating carbolines as the amido fragments. The novel complexes are screened both in vitro and ex vivo, against several cancer cell lines and high-grade serous ovarian cancer (HGSOC) tumoroids, respectively. Excellent cytotoxicity values are obtained for most complexes, while the structural variety of the CMA library screened thus far, provides promising leads for future developments. Variations of all three components (NHC, metal, amido ligand), enable the establishment of trends regarding cytotoxicity and selectivity towards cancerous over normal cells.

Recent advances on therapeutic potentials of gold and silver nanobiomaterials for human viral diseases

Viral diseases are prominent among the widely spread infections threatening human well-being. Real-life clinical successes of the few available therapeutics are challenged by pathogenic resistance and suboptimal delivery to target sites. Nanotechnology has aided the design of functionalised and non-functionalised Au and Ag nanobiomaterials through physical, chemical and biological (green synthesis) methods with improved antiviral efficacy and delivery. In this review, innovative designs as well as interesting antiviral activities of the nanotechnology-inclined biomaterials of Au and Ag, reported in the last 5 years were critically overviewed against several viral diseases affecting man. These include influenza, respiratory syncytial, adenovirus, severe acute respiratory syndromes (SARS), rotavirus, norovirus, measles, chikungunya, HIV, herpes simplex virus, dengue, polio, enterovirus and rift valley fever virus. Notably identified among the nanotechnologically designed promising antiviral agents include AuNP-M2e peptide vaccine, AgNP of cinnamon bark extract and AgNP of oseltamivir for influenza, PVP coated AgNP for RSV, PVP-AgNPs for SARS-CoV-2, AuNRs of a peptide pregnancy-induce d hypertension and AuNP nanocarriers of antigen for MERS-CoV and SARS-CoV respectively. Others are AgNPs of collagen and Bacillus subtilis for rotavirus, AgNPs labelled Ag30-SiO 2 for murine norovirus in water, AuNPs of Allium sativum and AgNPs of ribavirin for measles, AgNPs of Citrus limetta and Andrographis Paniculata for Chikungunya, AuNPs of efavirenz and stavudine, and AgNPs-curcumin for HIV, NPAuG3-S8 for HSV, AgNPs of Moringa oleifera and Bruguiera cylindrica for dengue while AgNPs of polyethyleneimine and siRNA analogues displayed potency against enterovirus. The highlighted candidates are recommended for further translational studies towards antiviral therapeutic designs.

Oxidative DNA cleavage mediated by a new unexpected [Pd(BAPP)][PdCl4] complex (BAPP = 1,4-bis(3-aminopropyl)piperazine): crystal structure, DNA binding and cytotoxic behavior

A novel Pd(ii) double complex, [Pd(BAPP)][PdCl4], containing the 1,4-bis(3-aminopropyl)piperazine (BAPP) ligand is investigated. X-ray crystallography of a single crystal confirmed the structure of the [Pd(BAPP)][PdCl4] complex. The spectroscopic behavior was also elucidated using elemental analysis, nuclear magnetic resonance and Fourier-transform infrared spectroscopy, and mass spectrometry. The antimicrobial susceptibility of the [Pd(BAPP)][PdCl4] complex against all tested microbial strains was lower than that of the BAPP ligand except for C. albicans. The cytotoxic impacts of the BAPP ligand and its [Pd(BAPP)][PdCl4] complex were evaluated in vitro for HepG2, CaCo-2 and MCF7 cell lines as well as the WI-38 normal cell line. The anticancer activity was markedly improved by the complexation. The [Pd(BAPP)][PdCl4] complex could selectively inhibit the tested cancer cells in a safe way to the non-tumorigenic cell (WI-38). From the DNA binding studies with ultraviolet-visible spectrophotometry, the [Pd(BAPP)][PdCl4] complex interacts more efficiently with the calf thymus DNA than its BAPP ligand through the intercalative binding mode. In the absence of an external reductant, the [Pd(BAPP)][PdCl4] complex cleaved the intact supercoiled pBR322 DNA under physiological conditions in a concentration-dependent manner. Additionally, electrophoretic experiments were performed in the presence of different radical scavengers, namely DMSO, NaN3 and KI, and ruled out the hydrolytic mechanistic pathway of the reaction and suggested that the oxidative mechanism is the preferred one. The results of the binding affinity of the [Pd(BAPP)][PdCl4] complex to human DNA were modeled using a molecular docking study showing that the complex interacts more strongly with human DNA than the ligand. Finally, an in vitro pharmacokinetic study was assessed through in silico ADME predictions.

Multicomponent synthesis of novel β-carboline-fused imidazolium derivatives via the Mannich reaction: cytotoxicity, molecular docking, and mechanistic studies as angiogenesis inhibitors

Herein we report novel multicomponent reactions for the synthesis of β-carboline-fused imidazolium derivatives via the Mannich-type reaction.

Natural and synthetic β-carboline as a privileged antifungal scaffolds

The discovery of antifungal agents with novel structure, broad-spectrum, low toxicity, and high efficiency has been the focus of medicinal chemists. Over the past decades, β-carboline scaffold has attracted extensive attention in the scientific community due to its potent and diverse biological activities with nine successfully marketed β-carboline-based drugs. In this review, we summarized the current states and advances in the antifungal activity of natural and synthetic β-carbolines. Additionally, the structure-activity relationships and their antifungal mechanisms targeting biofilm, cell wall, cell membrane, and fungal intracellular targets were also systematically discussed. In summary, β-carbolines have the great potential to develop new efficient scaffolds to combat fungal infections.