Novel Gold and Silver Carbene Complexes Exert Antitumor Effects Triggering the Reactive Oxygen Species Dependent Intrinsic Apoptotic Pathway

Anti-Breast Cancer Properties and In Vivo Safety Profile of a Bis-Carbazole Derivative

Background: Carbazoles represent one of the most important classes of nitrogen-based tricyclic aromatic heterocycles and are present in natural sources and chemically obtained drugs. Recently, several research groups disclosed their large biological and chemical applications in different fields, leading to an increased interest towards this class of molecules. Some of the obtained derivatives have been successfully employed in the clinical treatment of different tumor types, but the onset of heavy side effects impaired their efficacy and discouraged their use. Pursuing the aim of obtaining carbazoles with less negative features, a lot of chemically modified compounds have been produced and evaluated. Objectives/Methods: In this paper, we describe the in vitro and in vivo evaluation of a bis-carbazole derivative with strong anticancer properties against two breast cancer cell lines. Results: This compound has been found to impact the cell cytoskeleton dynamics, triggering the activation of some key proteins playing a role in the intrinsic and extrinsic apoptotic pathways. Equally important, this derivative has been found to be selective for cancer cells and has shown a safe profile in Balb/c-treated mice. Conclusions: Overall, the disclosed outcomes represent an important landmark for encouraging further studies directed toward the potentiation of this lead to be potentially exploited in both preclinical and clinical applications.

Advancements and challenges in brain cancer therapeutics

Treating brain tumors requires a nuanced understanding of the brain, a vital and delicate organ. Location, size, tumor type, and surrounding tissue health are crucial in developing treatment plans. This review comprehensively summarizes various treatment options that are available or could be potentially available for brain tumors, including physical therapies (radiotherapy, ablation therapy, photodynamic therapy, tumor-treating field therapy, and cold atmospheric plasma therapy) and non-physical therapies (surgical resection, chemotherapy, targeted therapy, and immunotherapy). Mechanisms of action, potential side effects, indications, and latest developments, as well as their limitations, are highlighted. Furthermore, the requirements for personalized, multi-modal treatment approaches in this rapidly evolving field are discussed, emphasizing the balance between efficacy and patient safety.

Design, synthesis and biological evaluation of multitarget hybrid molecules containing NHC-Au(I) complexes and carbazole moieties

N-heterocyclic carbenes (NHCs) represent suitable ligands for rapid and efficient drug design, because they offer the advantage of being easily chemically modified and can bind several substituents, including transition metals as, for instance, gold derivatives. Gold-NHC complexes possess various biological activities and were demonstrated good candidates as anticancer drugs. Besides, carbazole derivatives are characterized by various pharmacological properties, such as anticancer, antibacterial, anti-inflammatory, and anti-psychotropic. Amongst the latter, N-thioalkyl carbazoles were proved to inhibit cancer cells damaging the nuclear DNA, through the inhibition of human topoisomerases. Herein, we report the design, synthesis and biological evaluation of nine new hybrid molecules in which NHC-Au(I) complexes and N-alkylthiolated carbazoles are linked together, in order to obtain novel biological multitarget agents. We demonstrated that the lead hybrid complexes possess anticancer, anti-inflammatory and antioxidant properties, with a high potential as useful tools for treating distinct aspects of several diseases, amongst them cancer.

Metal complexes of backbone-halogenated imidazol-2-ylidenes

In this manuscript, literature reports on mono- and di-halogen (F, Cl, Br, and I) substituted at positions 4 or/and 4,5 imidazol-2-ylidene (NHC) metal complexes are discussed: particularly, their structural diversity with various metals (groups 6-13), important physicochemical properties, catalytic and medicinal/biological applications are reviewed. To our knowledge, there are no literature reports on group 4 and 5 metal complexes with this type of NHC ligands. Halogenated imidazol-2-ylidene metal complexes deserve special attention because halogens are the classic electron donating groups (mesomerically) in conjugated aromatic/heteroaromatic ring systems, but electron withdrawing inductively. However, they exhibit a significant electron withdrawing inductive effect, thus providing unique electronic properties. This is important for fine tuning of σ-donor abilities of the "carbenic" carbon of imidazol-2-ylidenes, which directly affect catalytic performance of their metal complexes. Other applications, advantages, and disadvantages of halogenated vs. unsubstituted imidazol-2-ylidene metal complexes are critically analyzed and summarized in this review.

Pd-, Cu-, and Ni-Catalyzed Reactions: A Comprehensive Review of the Efficient Approaches towards the Synthesis of Antibacterial Molecules

A strong synthetic tool for many naturally occurring chemicals, polymers, and pharmaceutical substances is transition metal-catalyzed synthesis. A serious concern to human health is the emergence of bacterial resistance to a broad spectrum of antibacterial medications. The synthesis of chemical molecules that are potential antibacterial candidates is underway. The main contributions to medicine are found to be effective in transition metal catalysis and heterocyclic chemistry. This review underlines the use of heterocycles and certain effective transition metals (Pd, Cu, and Ni) as catalysts in chemical methods for the synthesis of antibacterial compounds. Pharmaceutical chemists might opt for clinical exploration of these techniques due to their potential.

A promising future of metal-N-heterocyclic carbene complexes in medicinal chemistry: The emerging bioorganometallic antitumor agents

Metal complexes based on N-heterocyclic carbene (NHC) ligands have emerged as promising broad-spectrum antitumor agents in bioorganometallic medicinal chemistry. In recent decades, studies on cytotoxic metal-NHC complexes have yielded numerous compounds exhibiting superior cytotoxicity compared to cisplatin. Although the molecular mechanisms of these anticancer complexes are not fully understood, some potential targets and modes of action have been identified. However, a comprehensive review of their biological mechanisms is currently absent. In general, apoptosis caused by metal-NHCs is common in tumor cells. They can cause a series of changes after entering cells, such as mitochondrial membrane potential (MMP) variation, reactive oxygen species (ROS) generation, cytochrome c (cyt c) release, endoplasmic reticulum (ER) stress, lysosome damage, and caspase activation, ultimately leading to apoptosis. Therefore, a detailed understanding of the influence of metal-NHCs on cancer cell apoptosis is crucial. In this review, we provide a comprehensive summary of recent advances in metal-NHC complexes that trigger apoptotic cell death via different apoptosis-related targets or signaling pathways, including B-cell lymphoma 2 (Bcl-2 family), p53, cyt c, ER stress, lysosome damage, thioredoxin reductase (TrxR) inhibition, and so forth. We also discuss the challenges, limitations, and future directions of metal-NHC complexes to elucidate their emerging application in medicinal chemistry.

Synthesis, characterization, and biological evaluation of novel cobalt(II) complexes with β-diketonates: crystal structure determination, BSA binding properties and molecular docking study

In order to discover a new antibiotic drug with better or similar activity of the already existing drugs, a series of novel cobalt(II) complexes with β-diketonate as ligands is synthesized and tested on four strains of bacteria and four species of fungi. All compounds showed notable antimicrobial activity against all tested strains. More importantly, some cobalt(II) complexes displayed greater activity than ketoconazole. It is important to notice that on the tested strains Mucor mucedo and Penicillium italicum complex 2B showed five times better activity compared to ketoconazole, while complex 2D had two times better activity on Penicillium italicum strain compared to ketoconazole. Moreover, investigations with bovine serum albumin were performed. Investigations showed that the tested complexes have an appropriate affinity for binding to bovine serum albumin. In addition, the molecular docking study was performed to investigate more specifically the sites and binding mode of the tested cobalt(II) complexes with β-diketonate as ligands to bovine serum albumin, tyrosyl-tRNA synthetase, topoisomerase II DNA gyrase, and cytochrome P450 14 alpha-sterol demethylase. In conclusion, all the results indicated the great prospective of the novel cobalt complexes for some potential clinical applications in the future.

Acetylated galactopyranosyl N-heterocyclic monocarbene complexes of Silver(I) as novel anti-proliferative agents in a rhabdomyosarcoma cell line

Herein, four silver(I) complexes bearing acetylated d-galactopyranoside-based N-heterocyclic carbene ligands were synthesized and fully characterized by elemental analysis, NMR, and X-ray photoelectron spectroscopy. All complexes were obtained with an anomeric β-configuration and as monocarbene species. In this study, we investigated the biological effects of the silver(I) complexes 2a-d on the human rhabdomyosarcoma cell line, RD. Our results show concentration-dependent effects on cell density, growth inhibition, and activation of key signaling pathways such as Akt 1/2, ERK 1/2, and p38-MAPK, indicating their potential as anticancer agents. Notably, at 35.5 µM, the complexes induced mitochondrial network disruption, as observed with 2b and 2c, whereas with 2a, this disruption was accompanied by nuclear content release. These results provide insight into the utility of carbohydrate incorporated NHC complexes of silver(I) as new agents in cancer therapy.

NHC-Ag(I) and NHC-Au(I) Complexes with N-Boc-Protected α-Amino Acidate Counterions Powerfully Affect the Growth of MDA-MB-231 Cells

N-Heterocyclic carbene (NHC) metal complexes are attracting scientists' interest as an alluring class of metallodrugs. Indeed, the versatile functionalization of NHC ligands makes them optimal scaffolds to be developed in medicinal chemistry. Besides, amino acids are great biological ligands for metals, such as silver and gold, even though their use is still under-investigated. Aiming to shed light on the anticancer properties of this kind of complex, we investigated a series of silver and gold complexes, stabilized by NHC ligands and bearing carboxylate salts of tert-butyloxycarbonyl (Boc)-N-protected glycine and l-phenylalanine as anionic ligands. The most active complexes, AuM1Gly and AuM1Phe, powerfully affect the growth of MDA-MB-231 breast cancer cells, with IC50 values in the low nanomolar range. Further studies demonstrated the blockade of the human topoisomerase I activity and actin polymerization reaction at 0.001 μM. These unique features make these complexes very interesting and worthy to be used for future in vivo studies.

Development of 1-(2-aminophenyl)pyrrole-based amides acting as human topoisomerase I inhibitors

Topoisomerases are ubiquitous enzymes in the human body, particularly involved in cancer development and progression. Topoisomerase I (topoI) performs DNA relaxation reactions by "controlled rotation" rather than by "strand passage." The inhibition of topoI has become a useful strategy to control cancer cell proliferation. Nowadays, different compounds have undergone clinical trials, but the search for new molecular entities is necessary and benefits from medicinal chemistry efforts. Pyrrole-based compounds emerged as promising antiproliferative agents, with particular interest in breast cancer therapy and topoI inhibition. Starting from these observations and based on the scaffold-hopping approach, we developed a small library of 1-(2-aminophenyl)pyrrole-based amides (7a-f) as new anticancer agents. Tested on a panel of cancer cell lines, 7a-f displayed the most interesting profile in MDA-MB-231 cells, where the most active compounds, 7d-f, were able to induce death by apoptosis. Direct enzymatic assays and docking simulations on the topoI active site (PDB: 1A35) revealed the inhibitory activity and potential binding site for the newly developed 1-(2-aminophenyl)pyrrole-based amides.

Novel Thiazolidine-2,4-dione-trimethoxybenzene-thiazole Hybrids as Human Topoisomerases Inhibitors

Cancer is a complex and heterogeneous disease and is still one of the leading causes of morbidity and mortality worldwide, mostly as the population ages. Despite the encouraging advances made over the years in chemotherapy, the development of new compounds for cancer treatments is an urgent priority. In recent years, the design and chemical synthesis of several innovative hybrid molecules, which bring different pharmacophores on the same scaffold, have attracted the interest of many researchers. Following this strategy, we designed and synthetized a series of new hybrid compounds that contain three pharmacophores, namely trimethoxybenzene, thiazolidinedione and thiazole, and tested their anticancer properties on two breast cancer (MCF-7 and MDA-MB-231) cell lines and one melanoma (A2058) cell line. The most active compounds were particularly effective against the MCF-7 cells and did not affect the viability of the normal MCF-10A cells. Docking simulations indicated the human Topoisomerases I and II (hTopos I and II) as possible targets of these compounds, the inhibitory activity of which was demonstrated by the mean of direct enzymatic assays. Particularly, compound 7e was proved to inhibit both the hTopo I and II, whereas compounds 7c,d blocked only the hTopo II. Finally, compound 7e was responsible for MCF-7 cell death by apoptosis. The reported results are promising for the further design and synthesis of other analogues potentially active as anticancer tools.

Synthesis of Novel N-Heterocyclic Carbene-Ruthenium (II) Complexes, “Precious” Tools with Antibacterial, Anticancer and Antioxidant Properties

Ruthenium N-heterocyclic carbene (Ru-NHC) complexes show interesting physico-chemical properties as catalysts and potential in medicinal chemistry, exhibiting multiple biological activities, among them anticancer, antimicrobial, antioxidant, and anti-inflammatory. Herein, we designed and synthesized a new series of Ru-NHC complexes and evaluated their biological activities as anticancer, antibacterial, and antioxidant agents. Among the newly synthesized complexes, RANHC-V and RANHC-VI are the most active against triple-negative human breast cancer cell lines MDA-MB-231. These compounds were selective in vitro inhibitors of the human topoisomerase I activity and triggered cell death by apoptosis. Furthermore, the Ru-NHC complexes’ antimicrobial activity was studied against Gram-positive and -negative bacteria, revealing that all the complexes possessed the best antibacterial activity against the Gram-positive Staphylococcus aureus, at a concentration of 25 µg/mL. Finally, the antioxidant effect was assessed by DPPH and ABTS radicals scavenging assays, resulting in a higher ability for inhibiting the ABTS•+, with respect to the well-known antioxidant Trolox. Thus, this work provides encouraging insights for further development of novel Ru-NHC complexes as potent chemotherapeutic agents endowed with multiple biological properties.

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.

Biological Activities of Ruthenium NHC Complexes: An Update

Ruthenium N-heterocyclic carbene (NHC) complexes have unique physico-chemical properties as catalysts and a huge potential in medicinal chemistry and pharmacology, exhibiting a variety of notable biological activities. In this review, the most recent studies on ruthenium NHC complexes are summarized, focusing specifically on antimicrobial and antiproliferative activities. Ruthenium NHC complexes are generally active against Gram-positive bacteria, such as Bacillus subtilis, Staphylococcus aureus, Micrococcus luteus, Listeria monocytogenes and are seldom active against Gram-negative bacteria, including Salmonella typhimurium, Pseudomonas aeruginosa and Escherichia coli and fungal strains of Candida albicans. The antiproliferative activity was tested against cancer cell lines of human colon, breast, cervix, epidermis, liver and rat glioblastoma cell lines. Ruthenium NHC complexes generally demonstrated cytotoxicity higher than standard anticancer drugs. Further studies are needed to explore the mechanism of action of these interesting compounds.

Bottom-Up Strategy to Forecast the Drug Location and Release Kinetics in Antitumoral Electrospun Drug Delivery Systems

Electrospun systems are becoming promising devices usable for topical treatments. They are eligible to deliver different therapies, from anti-inflammatory to antitumoral. In the current research, polycaprolactone electrospun membranes loaded with synthetic and commercial antitumoral active substances were produced, underlining how the matrix-filler affinity is a crucial parameter for designing drug delivery devices. Nanofibrous membranes loaded with different percentages of Dacarbazine (the drug of choice for melanoma) and a synthetic derivative of Dacarbazine were produced and compared to membranes loaded with AuM1, a highly active Au-complex with low affinity to the matrix. AFM morphologies showed that the surface profile of nanofibers loaded with affine substances is similar to one of the unloaded systems, thanks to the nature of the matrix-filler interaction. FTIR analyses proved the efficacy of the interaction between the amidic group of the Dacarbazine and the polycaprolactone. In AuM1-loaded membranes, because of the weak matrix-filler interaction, the complex is mainly aggregated in nanometric domains on the nanofiber surface, which manifests a nanometric roughness. Consequently, the release profiles follow a Fickian behavior for the Dacarbazine-based systems, whereas a two-step with a highly prominent burst effect was observed for AuM1 systems. The performed antitumoral tests evidence the high-cytotoxic activity of the electrospun systems against melanoma cell lines, proving that the synthetic substances are more active than the commercial dacarbazine.

N-Heterocyclic Carbene (NHC) Silver Complexes as Versatile Chemotherapeutic Agents Targeting Human Topoisomerases and Actin

In recent years, the number of people suffering from cancer has risen rapidly and the World Health Organization and U.S. and European governments have identified this pathology as a priority issue. It is known that most bioactive anticancer molecules do not target a single protein but exert pleiotropic effects, simultaneously affecting multiple pathways. In our study, we designed and synthesized a new series of silver N-heterocyclic carbene (NHC) complexes [(NHC)2 Ag]+ [AgX2 ]- (X=iodide or acetate). The new complexes were active against two human breast cancer cell lines, MCF-7 and MDA-MB-231. These compounds showed multiple target actions as anticancer, by inhibiting in vitro the activity of the human topoisomerases I and II and interfering with the cytoskeleton dynamic, as also confirmed by in silico studies. Moreover, the antimicrobial activity of these silver complexes was studied against Gram-positive/negative bacteria. These dual properties provide a two-tiered approach, making these compounds of interest to be further deepened for the development of new chemotherapeutic agents.

Electrospun Membranes Designed for Burst Release of New Gold-Complexes Inducing Apoptosis of Melanoma Cells

Two non-commercial metallic Au-based complexes were tested against one of the most aggressive malignant melanomas of the skin (MeWo cells), through cell viability and time-lapse live-cell imaging system assays. The tests with the complexes were carried out both in the form of free metallic complexes, directly in contact with the MeWo cell line culture, and embedded in fibers of Polycaprolactone (PCL) membranes produced by the electrospinning technique. Membranes functionalized with complexes were prepared to evaluate the efficiency of the membranes against the melanoma cells and therefore their feasibility in the application as an antitumoral patch for topical use. Both series of tests highlighted a very effective antitumoral activity, manifesting a very relevant cell viability inhibition after both 24 h and 48 h. In the case of the AuM1 complex at the concentration of 20 mM, melanoma cells completely died in this short period of time. A mortality of around 70% was detected from the tests performed using the membranes functionalized with AuM1 complex at a very low concentration (3 wt.%), even after 24 h of the contact period. The synthesized complexes also manifest high selectivity with respect to the MeWo cells. The peculiar structural and morphological organization of the nanofibers constituting the membranes allows for a very effective antitumoral activity in the first 3 h of treatment. Experimental points of the release profiles were perfectly fitted with theoretical curves, which easily allow interpretation of the kinetic phenomena occurring in the release of the synthesized complexes in the chosen medium.

Recent development of gold(I) and gold(III) complexes as therapeutic agents for cancer diseases

Metal complexes have demonstrated significant antitumor activities and platinum complexes are well established in the clinical application of cancer chemotherapy. However, the platinum-based treatment of different types of cancers is massively hampered by severe side effects and resistance development. Consequently, the development of novel metal-based drugs with different mechanism of action and pharmaceutical profile attracts modern medicinal chemists to design and synthesize novel metal-based agents. Among non-platinum anticancer drugs, gold complexes have gained considerable attention due to their significant antiproliferative potency and efficacy. In most situations, the gold complexes exhibit anticancer activities by targeting thioredoxin reductase (TrxR) or other thiol-rich proteins and enzymes and trigger cell death via reactive oxygen species (ROS). Interestingly, gold complexes were recently reported to elicit biochemical hallmarks of immunogenic cell death (ICD) as an ICD inducer. In this review, the recent progress of gold(I) and gold(III) complexes is comprehensively summarized, and their activities and mechanism of action are documented.

Novel Au Carbene Complexes as Promising Multi-Target Agents in Breast Cancer Treatment

Over the past decade, metal complexes based on N-heterocyclic carbenes (NHCs) have attracted great attention due to their wide and exciting applications in material sciences and medicinal chemistry. In particular, the gold-based complexes are the focus of research efforts for the development of new anticancer compounds. Literature data and recent results, obtained by our research group, reported the design, the synthesis and the good anticancer activity of some silver and gold complexes with NHC ligands. In particular, some of these complexes were active towards some breast cancer cell lines. Considering this evidence, here we report some new Au-NHC complexes prepared in order to improve solubility and biological activity. Among them, the compounds 1 and 6 showed an interesting anticancer activity towards the breast cancer MDA-MB-231 and MCF-7 cell lines, respectively. In addition, in vitro and in silico studies demonstrated that they were able to inhibit the activity of the human topoisomerases I and II and the actin polymerization reaction. Moreover, a downregulation of vimentin expression and a reduced translocation of NF-kB into the nucleus was observed. The interference with these vital cell structures induced breast cancer cells' death by triggering the extrinsic apoptotic pathway.

Multidrug Resistance (MDR): A Widespread Phenomenon in Pharmacological Therapies

Multidrug resistance is a leading concern in public health. It describes a complex phenotype whose predominant feature is resistance to a wide range of structurally unrelated cytotoxic compounds, many of which are anticancer agents. Multidrug resistance may be also related to antimicrobial drugs, and is known to be one of the most serious global public health threats of this century. Indeed, this phenomenon has increased both mortality and morbidity as a consequence of treatment failures and its incidence in healthcare costs. The large amounts of antibiotics used in human therapies, as well as for farm animals and even for fishes in aquaculture, resulted in the selection of pathogenic bacteria resistant to multiple drugs. It is not negligible that the ongoing COVID-19 pandemic may further contribute to antimicrobial resistance. In this paper, multidrug resistance and antimicrobial resistance are underlined, focusing on the therapeutic options to overcome these obstacles in drug treatments. Lastly, some recent studies on nanodrug delivery systems have been reviewed since they may represent a significant approach for overcoming resistance.

Catalytic and Biological Activity of Silver and Gold Complexes Stabilized by NHC with Hydroxy Derivatives on Nitrogen Atoms

In this paper is reported the synthesis of N,N′ hydroxy derivative of NHC silver (3a–4a) and gold(I) (3b–4b) complexes of general formula [M(NHC)2]+ [MX2]−. All compounds were characterized by spectroscopic and analytic techniques. The complexes turned out to be effective in both catalytic and biological applications. They catalyzed the coupling of aldehyde, piperidine, and phenylacetylene in A3-reaction to produce propargylamines and showed antimicrobial activity. In fact, minimal inhibition concentration (MIC) tests with Gram-positive and Gram-negative bacteria demonstrated that the silver compounds are selective toward E. coli, whereas the gold analogues are active against S. aureus. Moreover, the N,N′ hydroxy derivative of NHC silver complexes 3a and 4a exhibited good anticancer activity on the HeLA cancer cells (3a-IC50 = 12.2 ± 0.1 µM, 4a-IC50 = 11.9 ± 1.2 µM), whereas gold complex 4b displayed good anticancer activity towards the MCF-7 cells (IC50 = 12.2 ± 1.2 µM).

Recent Advances in the Development of Thalidomide-Related Compounds as Anticancer Drugs

INTRODUCTION

Thalidomide is an old well-known drug that was first used as morning sickness relief in pregnant women before being withdrawn from the market due to its severe side effects on normal fetal development, However, over the last few decades, the interest in this old drug has been renewed because of its efficacy in several important disorders for instance, multiple myeloma, breast cancer, and HIV-related diseases due to its antiangiogenic and immunomodulatory properties. Unfortunately, even in these cases, many aftereffects as deep vein thrombosis, peripheral neuropathy, constipation, somnolence, pyrexia, pain, and teratogenicity have been reported, showing the requirement of careful and monitored use. For this reason, research efforts are geared toward the synthesis and optimization of new thalidomide analogues lacking in toxic effects to erase these limits and improve the pharmacological profile.

AIMS

This review aims to examine the state-of-the-art concerning the current studies on thalidomide and its analogues towards cancer diseases (with few hints regarding the antimicrobial activity), focusing the attention on the possible mechanisms of action involved and the lack of toxicity.

CONCLUSION

In the light of the collected data, thalidomide analogues and their ongoing optimization could lead, in the future, to the realization of a promising therapeutic alternative for cancer-fighting.

N-Heterocyclic Carbene-Gold(I) Complexes Targeting Actin Polymerization

Transition metal complexes are attracting attention because of their various chemical and biological properties. In particular, the NHC-gold complexes represent a productive field of research in medicinal chemistry, mostly as anticancer tools, displaying a broad range of targets. In addition to the already known biological targets, recently, an important activity in the organization of the cell cytoskeleton was discovered. In this paper, we demonstrated that two NHC-gold complexes (namely AuL4 and AuL7) possessing good anticancer activity and multi-target properties, as stated in our previous studies, play a major role in regulating the actin polymerization, by the means of in silico and in vitro assays. Using immunofluorescence and direct enzymatic assays, we proved that both the complexes inhibited the actin polymerization reaction without promoting the depolymerization of actin filaments. Our outcomes may contribute toward deepening the knowledge of NHC-gold complexes, with the objective of producing more effective and safer drugs for treating cancer diseases.

A Phenylacetamide Resveratrol Derivative Exerts Inhibitory Effects on Breast Cancer Cell Growth

Resveratrol (RSV) is a natural compound that displays several pharmacological properties, including anti-cancer actions. However, its clinical application is limited because of its low solubility and bioavailability. Here, the antiproliferative and anti-inflammatory activity of a series of phenylacetamide RSV derivatives has been evaluated in several cancer cell lines. These derivatives contain a monosubstituted aromatic ring that could mimic the RSV phenolic nucleus and a longer flexible chain that could confer a better stability and bioavailability than RSV. Using MTT assay, we demonstrated that most derivatives exerted antiproliferative effects in almost all of the cancer cell lines tested. Among them, derivative 2, that showed greater bioavailability than RSV, was the most active, particularly against estrogen receptor positive (ER+) MCF7 and estrogen receptor negative (ER-) MDA-MB231 breast cancer cell lines. Moreover, we demonstrated that these derivatives, particularly derivative 2, were able to inhibit NO and ROS synthesis and PGE2 secretion in lipopolysaccharide (LPS)-activated U937 human monocytic cells (derived from a histiocytoma). In order to define the molecular mechanisms underlying the antiproliferative effects of derivative 2, we found that it determined cell cycle arrest at the G1 phase, modified the expression of cell cycle regulatory proteins, and ultimately triggered apoptotic cell death in both breast cancer cell lines. Taken together, these results highlight the studied RSV derivatives, particularly derivative 2, as promising tools for the development of new and more bioavailable derivatives useful in the treatment of breast cancer.

Gold Derivatives Development as Prospective Anticancer Drugs for Breast Cancer Treatment

Commonly used anticancer drugs are cisplatin and other platinum-based drugs. However, the use of these drugs in chemotherapy causes numerous side effects and the onset of frequent drug resistance phenomena. This review summarizes the most recent results on the gold derivatives used for their significant inhibitory effects on the in vitro proliferation of breast cancer cell models and for the consequences deriving from morphological changes in the same cells. In particular, the study discusses the antitumor activity of gold nanoparticles, gold (I) and (III) compounds, gold complexes and carbene-based gold complexes, compared with cisplatin. The results of screening studies of cytotoxicity and antitumor activity for the gold derivatives show that the death of cancer cells can occur intrinsically by apoptosis. Recent research has shown that gold (III) compounds with square planar geometries, such as that of cisplatin, can intercalate the DNA and provide novel anticancer agents. The gold derivatives described can make an important contribution to expanding the knowledge of medicinal bioorganometallic chemistry and broadening the range of anticancer agents available, offering improved characteristics, such as increased activity and/or selectivity, and paving the way for further discoveries and applications.

Schiff Bases: Interesting Scaffolds with Promising Antitumoral Properties

Schiff bases, named after Hugo Schiff, are highly reactive organic compounds broadly used as pigments and dyes, catalysts, intermediates in organic synthesis, and polymer stabilizers. Lots of Schiff bases are described in the literature for various biological activities, including antimalarial, antibacterial, antifungal, anti-inflammatory, and antiviral. Schiff bases are also known for their ability to form complexes with several metals. Very often, complexes of Schiff bases with metals and Schiff bases alone have demonstrated interesting antitumor activity. Given the innumerable vastness of data regarding antitumor activity of all these compounds, we focused our attention on mono- and bis-Schiff bases alone as antitumor agents. We will highlight the most significant examples of compounds belonging to this class reported in the literature.

Anticancer Activity of Leonurus sibiricus L.: Possible Involvement of Intrinsic Apoptotic Pathway

Liver cancer is the most common cause of mortality in men and women. The aim of this study was to evaluate the methanolic extract of aerial parts of Leonurus sibiricus L (LS) for its anticancer activity on HCC cell lines. Human HCC cell lines, Huh-7 and HSC-T6 were used for cytotoxicity assay, determination of ROS and gene expression analysis (p53, Bcl-2, Bax, caspase-3, caspase-8, and caspase-9). Western blotting was used to assess ERK, AKT, and Caspase-3 activation. HPLC-MS analysis was also performed to determine the phytochemicals present in LS-M extract. LS-M extract has increased the expression of proapoptotic genes, including p53, Bax, and caspase-9 and down-regulated the activation of ERK and Akt. The caspase-3 activity as well as the ROS generation were significantly increased in a dose-dependent manner compared to control. The carotenoids, lutein and beta carotene present in LS-M extract exhibited anticancer activity. In overall, the methanolic extract of LS induces apoptosis in Huh-7 as well as in HSC-T6 cells possibly involving a ROS-mediated mitochondrial signaling pathway.

Newly Synthesized Imino-Derivatives Analogues of Resveratrol Exert Inhibitory Effects in Breast Tumor Cells

Breast cancer represents the most frequently diagnosed malignancy in women worldwide. Various therapeutics are currently used in order to halt the progression of breast tumor, even though certain side effects may limit the beneficial effects. In recent years, many efforts have been addressed to the usefulness of natural compounds as anticancer agents due to their low toxicity. Resveratrol, a stilbene found in grapes, berries, peanuts and soybeans, has raised a notable interest for its antioxidant, anti-inflammatory, and antitumor properties. Here, we report the design, the synthesis and the characterization of the anticancer activity of a small series of imino N-aryl-substituted compounds that are analogues of resveratrol. In particular, the most active compound, named 3, exhibited anti-tumor activity in diverse types of breast cancer cells through the inhibition of the human topoisomerase II and the induction of apoptotic cell death. Therefore, the abovementioned compound maybe considered as a promising agent in more comprehensive treatments of breast cancer.

α-ω Alkenyl-bis-S-Guanidine Thiourea Dihydrobromide Affects HeLa Cell Growth Hampering Tubulin Polymerization

Cancer is going to be the first cause of mortality worldwide in the 21th century. It is considered a multifactorial disease that results from the combined influence of many genetic aberrations, leading to abnormal cell proliferation. As microtubules are strongly implicated in cellular growth, they represent an important target for cancer treatment. The well-known microtubule-targeting agents (MTAs) including paclitaxel, colchicine and vinca alkaloids are commonly used in the treatment of various cancers. However, adverse effects and drug resistance are major limitations in their clinical use. To find new candidates able to induce microtubule alteration with reduced toxic effects or drug resistance, we studied a small new series of derivatives that present imidazolinic, guanidinic, thioureidic and hydrazinic groups (1-9). All the compounds were tested for their antitumor activity against a panel of six tumoral cell models. In particular, compound 8 (nonane-1,9-diyl-bis-S-amidinothiourea dihydrobromide) showed the lowest IC₅₀ value against HeLa cells, together with a low cytotoxicity for normal cells. This compound was able to induce the apoptotic mitochondrial pathway and inhibited tubulin polymerization with a similar efficacy to vinblastine and nocodazole. Taken together, these promising biological properties make compound 8 useful for the development of novel therapeutic approaches in cancer treatment.

Metalo components exhibiting significant anticancer and antibacterial properties: a novel sandwich-type like polymeric structure

Four new dicyanoargentate(I)-based complexes 1-4 were synthesized from certain metal ions with a tetradentate ligand [N, N-bis (2-hydroxyethyl) -ethylenediamine; N-bishydeten] and determined by diverse procedures (elemental, thermal, FT-IR, ESI-MS for 1-3 and, magnetic susceptibility and EPR for 1, and 2) including crystal analysis of 4. The crystal method revealed that complex 4 has a sandwich-type like polymeric chemical structure with layers formed by [Cd(N-bishydeten)2]2+ cations and [Ag(CN)2]- anions. The complexes were further characterized by fluorescence and UV spectroscopy to determine their physicochemical features. The complexes displayed a DNA binding activity within the same range as found for cisplatin, in addition to their strong stability in the presence of the physiological buffer system. The complexes were also investigated for pharmacological properties like interaction with DNA/Bovine serum albumin, anticancer and antibacterial activities. Physicochemical studies of DNA with the complexes suggested that the interaction mode between them are possibly both intercalative and groove binding types. These spectroscopic measurements also show that there may be a binding tendency between BSA and the complexes via hydrogen or Van der Waals bonds. The viability tests demonstrated that all the complexes exhibited antibacterial (1-4) and anticancer effects (2-4) toward ten diverse bacterial strains and three tumor cells (HT-29 colon adenocarcinoma, HeLa cervical cancer, and C6 glioma), respectively.

The Cytotoxic Effect of Newly Synthesized Ferrocenes against Cervical Carcinoma Cells Alone and in Combination with Radiotherapy

Cervical cancer is one of the most common types of cancer in women, with approximately 500,000 new cases and 250,000 deaths every year. Radiotherapy combined with chemotherapy represents the treatment of choice for advanced cervical carcinomas. The role of the chemotherapy is to increase the sensitivity of the cancer cells to irradiation. Cisplatin, the most commonly used drug for this purpose, has its limitations. Thus, we used a family of ferrocene derivatives (in addition, one new species was prepared using standard Schlenk techniques) and studied their effects on cervical cancer cells alone and in combination with irradiation. We applied colorimetric assay to determine the cytotoxicity of the compounds; flow cytometry to analyze the production of reactive oxygen species (ROS), cell cycle, and mitochondrial membrane potential (MMP); immunochemistry to study protein expression; and colony forming assay to evaluate changes in radiosensitivity. Treatment with ferrocenes exhibited significant cytotoxicity against cervical cancer cells, associated with increasing ROS production and MMP changes, suggesting the induction of apoptosis. The combined activity of ferrocenes and ionizing radiation highlighted ferrocenes as potential radiosensitizing drugs, while their higher single-agent toxicity in comparison with routinely used cisplatin could also be promising. Our results demonstrate antitumor activity of several tested ferrocenes both alone and in combination with radiotherapy.

Development of four ruthenium polypyridyl complexes as antitumor agents: Design, biological evaluation and mechanism investigation

Ruthenium complexes are expected to be new opportunities for the development of antitumor agents. Herein, four ruthenium polypyridyl complexes ([Ru(bpy)₂(CAPIP)](ClO₄)₂ (Ru(II)-1, bpy = 2,2'-bipyridine; CAPIP = (E)-2-(2-(furan-2-yl)vinyl)-1H-imidazo[4,5-f][1,10]phenanthroline), [Ru(phen)₂(CA-PIP)](ClO₄)₂ (Ru(II)-2, phen = 1,10-phenanthroline), [Ru(dmb)₂(CAPIP)](ClO₄)₂ (Ru(II)-3, dmb = 4,4'-dimethyl-2,2'-bipyridine), [Ru(dmb)₂(ETPIP)](ClO₄)₂ (Ru(II)-4, ETPIP = 2-(4-(thiophen-2-ylethynyl)phenyl)-1H-imidazo[4,5-f][1,10]phen-anthroline)) have been investigated as mitochondria-targeted antitumor metallodrugs. DNA binding studies indicated that target Ru(II) complexes interacts with CT DNA (calf thymus DNA) by an intercalative mode. Cytotoxicity assay results demonstrate that Ru(II) complexes show high cytotoxicity against A549 cells with low IC₅₀ value of 23.6 ± 2.3, 20.1 ± 1.9, 22.7 ± 1.8 and 18.4 ± 2.3 μM, respectively. Flow cytometry and morphological analysis revealed that these Ru(II) complexes can induce apoptosis in A549 cells. Intracellular reactive oxygen species (ROS) and mitochondrial membrane potential were also investigated by ImageXpress Micro XLS system. The experimental results indicate that the reactive oxygen species in A549 cells increased significantly and mitochondrial membrane potential decreased obviously. In addition, colocalization studies shown these complexes could get to the cytoplasm through the cell membrane and accumulate in the mitochondria. Furthermore, Ru(II) complexes can effectively induces cell cycle arrest at the S phase in A549 cells. Finally, cell invasion assay and quantitative studies were also performed to investigate the mechanism of this process. All in together, this study suggested that these Ru(II) complexes could induce apoptosis in A549 cells through cell cycle arrest and ROS-mediated mitochondrial dysfunction pathway.

Is the Way to Fight Cancer Paved with Gold? Metal-Based Carbene Complexes with Multiple and Fascinating Biological Features

Herein, we report the synthesis and the multiple anti-tumor properties of new gold and silver carbene complexes. The chemical modifications, grounded on our previous studies, led us to identify a good lead complex, gold-based, whose biological features are very exciting and promising in the anti-cancer research and could be further developed. Indeed, the bis-[4,5-dichloro-(N-methyl-N’(2-hydroxy-2-phenyl)ethyl-imidazole-2-ylidene)gold(I)]⁺[dichloro-gold]⁻ (AuL7) complex possesses the ability to interfere with at least three important and different intracellular targets, namely the human topoisomerases I and II and tubulin, which are able to modulate metabolic processes not directly correlated each other. We proved that the modifications of the ligands structure in AuL7, with respect to another already published complex, i.e., bis-[4,5-dichloro-(N-methyl-N’(cyclopentane-2ol)-imidazole-2-ylidine)gold(I)]⁺[dichloro-gold]⁻ (AuL4), produce a different behavior toward tubulin-polymerization process, since AuL7 is a tubulin-polymerization inhibitor and AuL4 a stabilizer, with the final same result of hampering the tumor growth. Taken together, our outcomes designate AuL7 as a promising compound for the development of multi-targeted anti-cancer therapies.

New ruthenium polypyridyl complexes functionalized with fluorine atom or furan: Synthesis, DNA-binding, cytotoxicity and antitumor mechanism studies

Two novel ruthenium(II) polypyridyl complexes, namely, [Ru(dmp)₂(CAPIP)](ClO₄)₂ (Ru(II)-1) and [Ru(dmp)₂(CFPIP)](ClO₄)₂ (Ru(II)-2), which respectively contain (E)-2-(2-(furan-2-yl)vinyl)-1H-imidazo[4,5-f][1,10]phen-anthroline (CAPIP) and (E)-2-(4-fluorostyryl)-1H-imidazo[4,5-f][1,10]phenanthroline. (CFPIP), were first designed and characterized (dmp = 2,9-dimethyl-1,10-phenanthroline). DNA binding experiments indicated that Ru(II) complexes interact with CT DNA through intercalative mode. In addition, the complexes Ru(II)-1 and Ru(II)-2, showed remarkable cell cytotoxicity, giving the respective IC₅₀ values of 4.1 ± 1.4 μM and 6.1 ± 1.4 μM on the A549 cancer cells. These values indicated higher activity than CAPIP, CFPIP, cisplatin (8.2 ± 1.4 μM) and other corresponding Ru(II) polypyridyl complexes. Furthermore, the Ru(II) complexes could arrive the cytoplasm through the cell membrane and accumulate in the mitochondria. Significantly, complexes Ru(II)-1 and Ru(II)-2 induced A549 cells apoptosis was mediated by increase of ROS levels and dysfunction of mitochondria, and resulted in cell cycle arrest and increased anti-migration activity on A549 cells. Overall, these results indicated that complexes Ru(II)-1 and Ru(II)-2 could be suitable candidates for further investigation as a chemotherapeutic agent in the treatment of tumors.

Antibacterial Therapeutic Agents Composed of Functional Biological Molecules

Antibacterial agents are a group of materials that selectively destroy bacteria by interfering with bacterial growth or survival. With the emergence of resistance phenomenon of bacterial pathogens to current antibiotics, new drugs are frequently entering into the market along with the existing drugs, and the alternative compounds with antibacterial functions are being explored. Due to the advantages of their inherent biochemical and biophysical properties including precise targeting ability, biocompatibility, biodegradability, long blood circulation time, and low cytotoxicity, biomolecules such as peptides, carbohydrates, and nucleic acids have huge potential for the antimicrobial application and have been extensively studied in recent years. In this review, antimicrobial therapeutic agents composed of three kinds of functional biological molecules were summarized. In addition, the research progress of antibacterial mechanism, chemical modification, and nanoparticle coupling of those biomolecules were also discussed.

Anchusa azurea Mill. (Boraginaceae) aerial parts methanol extract interfering with cytoskeleton organization induces programmed cancer cells death

The present study aimed to determine the chemical composition, antioxidant effects and antitumor properties of a methanol extract of Anchusa azurea Mill. (Boraginaceae) aerial parts against four tumour cell lines (MCF-7, MDA-MB-231, RKO, and R2C). The antioxidant effects were assessed by using β-carotene bleaching, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing ability power (FRAP) tests. HPLC analyses revealed chlorogenic acid, catechin, caffeic acid, and astragalin as the most abundant compounds. Interesting results were obtained in the β-carotene bleaching test with IC50 values of 7.6 and 27.5 μg mL-1 after 30 and 60 min of incubation, respectively. Furthermore, the A. azurea extract protects 3T3-L1 mouse cells from oxidative stress induced by menadione and exhibits good antitumor activity, with very low toxicity. Our data indicate that the antitumor properties are due to the ability to induce programmed cancer cell death through caspase 3/7 and 9 activation and interference with the cytoskeleton dynamics.

β-Caryophyllene: A Sesquiterpene with Countless Biological Properties

β-Caryophyllene (BCP), a natural bicyclic sesquiterpene, is a selective phytocannabinoid agonist of type 2 receptors (CB2-R). It isn’t psychogenic due to the absence of an affinity to cannabinoid receptor type 1 (CB1). Among the various biological activities, BCP exerts anti-inflammatory action via inhibiting the main inflammatory mediators, such as inducible nitric oxide synthase (iNOS), Interleukin 1 beta (IL-1β), Interleukin-6 (IL-6), tumor necrosis factor-alfa (TNF-α), nuclear factor kapp a-light-chain-enhancer of activated B cells (NF-κB), cyclooxygenase 1 (COX-1), cyclooxygenase 2 (COX-2). Peroxisome proliferator-activated receptors alpha (PPAR-α) effects are also mediated by the activation of PPAR-α and PPAR-γ receptors. In detail, many studies, in vitro and in vivo, suggest that the treatment with β-caryophyllene improves the phenotype of animals used to model various inflammatory pathologies, such as nervous system diseases (Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, amyotrophic lateral sclerosis, stroke), atherosclerosis, and tumours (colon, breast, pancreas, lymphoma, melanoma and glioma cancer). Furthermore, pre-clinical data have highlighted that BCP is potentially useful in Streptococcus infections, osteoporosis, steatohepatitis, and exerts anticonvulsant, analgesic, myorelaxing, sedative, and antidepressive effects. BCP is non-toxic in rodents, with a Lethal dose, 50% (LD50) greater than 5000 mg/kg. Nevertheless, it inhibits various cytochrome P450 isoforms (above all, CYP3A4), which metabolise xenobiotics, leading to adverse effects, due to drug levels over therapeutic window. All the reported data have highlighted that both pharmacological and toxicological aspects need to be further investigated with clinical trials.

Blue-emitting acridine-tagged silver(i)-bis-N-heterocyclic carbene

Herein, the photophysical properties of an acridine derivative of a bis-N-heterocyclic carbene silver complex were investigated. The HOMO and LUMO energy differences between 9-[(N-methyl imidazol-2-ylidene)]acridine and 4,5-bis[(N-methyl-imidazol-2-ylidene)methyl]acridine were theoretically compared. Based on the calculation, the 4,5-bis N-heterocyclic carbene-tethered acridine type of ligand was found to be a potential source for tuning the fluorescent nature of the resultant metal derivatives. Thus, a 4,5-bis N-heterocyclic carbene (NHC)-tethered acridine silver(i) salt was synthesized, and its photophysical properties were investigated. The 4,5-bis[(N-isopropylimidazol-2-ylidene)methyl]acridine silver(i) hexafluorophosphate complex was obtained from the reaction between [4,5-bis{(N-isopropylimidazolium)methyl}acridine] hexafluorophosphate and Ag₂O in very good yield; this molecule was characterized by elemental analysis and FTIR, multinuclear (¹H and ¹³C) NMR, UV-Vis, and fluorescence spectroscopic techniques. The molecular structure has been confirmed by single-crystal X-ray diffraction analysis, which has revealed that the complex is a homoleptic mononuclear silver(i) cationic solid. The charge of the Ag(i)–NHC cation is balanced by the hexafluorophosphate anion. The cationic moieties are closely packed in the chair and inverted chair forms where silver(i) possesses a quasi-linear geometry. Moreover, the silver complex provided blue emission from all the three excitations with good fluorescence quantum yield. The fluorescence lifetime of the silver(i) complex has been determined using the time-correlated single photon counting technique. Interestingly, the fluorescence decay pattern and the fluorescence lifetimes of the silver complex are largely different from those of the parent ligand acridine imidazolium salt. Moreover, the theoretical predictions have been found to be in good agreement with the experimental results.

The synthesis and photophysical properties of blue-emitting acridine-tagged silver(i)-bis-N-heterocyclic carbene are reported.

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.

In vitro biological properties and predicted DNA–BSA interaction of three new dicyanidoargentate(i)-based complexes: synthesis and characterization

The synthesis, characterization and biological activity of three novel dicyanidoargentate(i)-based complexes are reported. The in vitro results show that these complexes may be potent antiproliferative drug candidates.