L-Ornithine Schiff base-copper and -cadmium complexes as new proteasome inhibitors and apoptosis inducers in human cancer cells

A comprehensive review on the development of chiral Cu, Ni, and Zn complexes as pharmaceutical agents over the past decades: Synthesis, molecular structure and biological activity

Chirality is a fundamental and widespread geometric structural property in living organisms that most biomacromolecules including nucleic acids, proteins and enzymes, possess. Consequently, the development of chiral drugs capable of binding specific targets have gradually gained wide attention in recent decades due to their selective effects on a broad spectrum of biological events ranging from cell metabolism to cell fate. In this context, the synthesis of chiral compounds as promising therapeutic candidates has assumed a major role in drug discovery. Among them, chiral metal complexes have attracted considerable interest due to their unique and intriguing structural features that could enable overcoming side effects and drug-resistance phenomena of metal-based drugs currently in the market such as cisplatin. In the current scenario, an in-depth overview of non-platinum chiral complexes needs to be presented and carried forward. Therefore, in this perspective article, an update of the scientific development of bioactive chiral copper, zinc and nickel complexes have been reported since they have not been thoroughly reviewed so far. Specifically, we focused the article mainly on metal complexes containing chiral ligands (type 2 chirality) as in literature they are more numerous than those with chirality at the metal center (type 1 chirality). Herein, not only their biological activity but also their mechanism of action is summarized. Furthermore, in the final section of the article we have highlighted copper-based complexes as those with a superior biological activity profile and greater prospects for development as a drug.

Advances in Coordination Chemistry of Schiff Base Complexes: A Journey from Nanoarchitectonic Design to Biomedical Applications

Since the discovery of Schiff bases over one and a half centuries ago, there has been tremendous research activity in the design of various Schiff bases and examination of their diverse structures and versatile applications. This family of compounds has continued to captivate many research groups due to the simplicity of their synthesis through the condensation of amines with carbonyl compounds. While conventional synthesis has been the most widely used, green synthetic methodologies have been also explored for this reaction, including sonication, microwave-assisted, natural acid-catalyzed and mechanochemical syntheses as well as utilizing ionic liquid solvents or deep eutectic solvents. Schiff bases have been utilized as excellent ligands for coordination to transition metals and late transition metals (lanthanides and actinides). These Schiff base compounds can be mono-, di-, or polydentate ligands. The aim of this review is to examine the biological applications of Schiff base complexes over the past decade with particular focus on their antimicrobial, antiviral, anticancer, antidiabetic, and anti-inflammatory activity. Schiff base complexes have been found effective in combating bacterial and fungal infections with numerous examples in the literature. The review addressed this area by focusing on the very recent examples while using tables to summarize the vast breadth of research according to the metallic moieties. Viruses have continued to be a target of many researchers in light of their continuous mutations and impact on human health, and therefore some examples of Schiff base complexes with antiviral activity are described. Cancer continues to be among the leading causes of death worldwide. In this article, the use of Schiff base complexes for, and the mechanisms associated with, their anticancer activity are highlighted. The production of reactive oxygen species (ROS) or intercalation with DNA base pairs leading to cell cycle arrest were the main mechanisms described. While there have been some efforts made to use Schiff base complexes as antidiabetic or anti-inflammatory agents, there are limited examples when compared with antimicrobial and anticancer studies. The conclusion of this review highlights the emerging areas of research and future perspectives with an emphasis on the potential uses of Schiff bases in the treatment of infectious and noninfectious diseases.

Mechanisms associated with cuproptosis and implications for ovarian cancer

Ovarian cancer, a profoundly fatal gynecologic neoplasm, exerts a substantial economic strain on nations globally. The formidable challenge of its frequent relapse necessitates the exploration of novel cytotoxic agents, efficacious antineoplastic medications with minimal adverse effects, and strategies to surmount resistance to primary chemotherapeutic agents. These endeavors aim to supplement extant pharmacological interventions and elucidate molecular mechanisms underlying induced cytotoxicity, distinct from conventional therapeutic modalities. Recent scientific research has unveiled a novel form of cellular demise, known as copper-death, which is contingent upon the intracellular concentration of copper. Diverging from conventional mechanisms of cellular demise, copper-death exhibits a pronounced reliance on mitochondrial respiration, particularly the tricarboxylic acid (TCA) cycle. Tumor cells manifest distinctive metabolic profiles and elevated copper levels in comparison to their normal counterparts. The advent of copper-death presents alluring possibilities for targeted therapeutic interventions within the realm of cancer treatment. Hence, the primary objective of this review is to present an overview of the proteins and intricate mechanisms associated with copper-induced cell death, while providing a comprehensive summary of the knowledge acquired regarding potential therapeutic approaches for ovarian cancer. These findings will serve as valuable references to facilitate the advancement of customized therapeutic interventions for ovarian cancer.

Synthesis, characterization, and cytotoxic effects of new copper complexes using Schiff-base derivatives from natural sources

Copper(II) complexes are interesting for cancer treatment due to their unique properties, including their redox potential, possible coordination structures with different ligands, the most diverse geometries, and different biomolecule reactivity. The present work synthesized new copper(II) complexes with Schiff-base (imine) type ligands using natural aldehydes such as cinnamaldehyde, vanillin, or ethyl vanillin. The ligands were obtained through the reaction of these aldehydes with the amines 1,3-diaminopropane, 2,2-dimethyl-1,3-propanediamine, or 1,3-diamino-2-propanol and characterized by 1H and 13C NMR, FTIR and ESI-HRMS. The complexation reaction used copper(II) as perchlorate salt, obtaining six new copper(II) complexes. The complexes were characterized using FTIR, UV-vis, elemental analysis, ESI-HRMS, and EPR. In addition, the interaction with the copper(II) complexes and serum albumin was investigated by electronic absorption, showing complex incorporation in the albumin structure. The cytotoxicity of the complexes was evaluated using MTT assay in neuroblastoma cell lines SH-SY5Y, CHP 212, and glioblastoma LN-18, and presented EC50 values between 90 and 300 μM. Based on our results, a square-planar copper(II) complex derived from Schiff-base cinnamaldehyde was found here to possess significant potential as an anti-cancer treatment. Further investigation is required to explore this compound's benefits in cancer co-treatment approaches fully.

Design, synthesis, molecular modeling, and bioactivity evaluation of 1,10-phenanthroline and prodigiosin (Ps) derivatives and their Copper(I) complexes against mTOR and HDAC enzymes as highly potent and effective new anticancer therapeutic drugs

Breast cancer is the second type of cancer with a high probability of brain metastasis and has always been one of the main problems of breast cancer research due to the lack of effective treatment methods. Demand for developing an effective drug against breast cancer brain metastasis and finding molecular mechanisms that play a role in effective treatment are gradually increasing. However, there is no effective anticancer therapeutic drug or treatment method specific to breast cancer, in particular, for patients with a high risk of brain metastases. It is known that mTOR and HDAC enzymes play essential roles in the development of breast cancer brain metastasis. Therefore, it is vital to develop some new drugs and conduct studies toward the inhibition of these enzymes that might be a possible solution to treat breast cancer brain metastasis. In this study, a series of 1,10-phenanthroline and Prodigiosin derivatives consisting of their copper(I) complexes have been synthesized and characterized. Their biological activities were tested in vitro on six different cell lines (including the normal cell line). To obtain additional parallel validations of the experimental data, some in silico modeling studies were carried out with mTOR and HDAC1 enzymes, which are very crucial drug targets, to discover novel and potent drugs for breast cancer and related brain metastases disease.

Syntheses, crystal structure, thermal behavior, and anti-tumor activity of three ternary metal complexes with 2-chloro-5-nitrobenzoic acid and heterocyclic compounds

Three complexes, namely complex (1), complex (2), and complex (3), were synthesized and characterized by X-ray diffraction, thermogravimetric study, and elemental study. Complex (1) comprises discrete binuclear clusters, where two oxygen atoms of 2-chloro-5-nitrobenzoic acid bridge the two copper atoms. Complex (2) is a six-coordination structure consisting of four nitrogen atoms and two oxygen atoms in 2-chloro-5-nitrobenzoic acid and 1,10-phenanthroline to furnish a twisted octahedron. Complex (3) is a six-coordination structure consisting of four oxygen atoms and two nitrogen atoms from the 2-chloro-5-nitrobenzoic acid, methanol, and 2,2′-dipyridyl to furnish a distorted octahedral geometry. Metal complexes’ anti-tumor activity was also investigated by the MTT assay. Of the complexes tested, complex (1) could induce apoptosis in these A549 lung cancer and Caco-2 colon adenocarcinoma cells and complex (2) could induce apoptosis in Caco-2 colon adenocarcinoma cells. CCDC for complex (1) was 1543354, CCDC for complex (2) was 1546991, and CCDC for complex (3) was 1543417.

Synthesis and antitumor activities of transition metal complexes of a bis-Schiff base of 2-hydroxy-1-naphthalenecarboxaldehyde

The complexes of Schiff base have attracted much attention for their potential biological activities. In this research, five transition metal complexes TM₃L₂(OAc)₂ (TM = Cu, 1; Ni, 2; Co, 3; Mn, 4; Fe, 5) were prepared using a bis-Schiff base of N,N'-bis[(2-hydroxy-1-naphthalenyl)methylene]-propane-1,3-diamine (H₂L), which present similar linear trinuclear structures with their three metal ions consolidated by two bis-Schiff base ligands and two acetate ligands. Their antitumor activities in vitro were screened through seven human cancer cell lines by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It revealed that complexes 1, 2 and 5 show much higher antitumor activities than the bis-Schiff base ligand and complexes 3 and 4, and even than cisplatin. Among them, complex 1 has the highest inhibitory effects on tumor cells with its IC₅₀ value (half-inhibitory concentration) being less than 0.5 μM for human bladder cancer cell line T-24, at which concentration complex 1 shows nearly no toxicity to the normal cell HL-7702 as revealed by flow cytometry. All of these demonstrate a potential anti-cancer candidate for complex 1, which induces tumor cell apoptosis by blocking T-24 tumor cells at the G2/M phase of the cell cycle, reducing mitochondrial membrane potential, increasing the concentration of reactive oxygen species and Ca²⁺ in the cell, and changing the expression of proteins.

Novel Copper Complexes That Inhibit the Proteasome and Trigger Apoptosis in Triple-Negative Breast Cancer Cells

Five innovative ternary copper(II) complexes [Cu(OH-PIP)(Phe)Cl](1), [Cu(OH-PIP)(Gly)(H2O)]NO3·2H2O (2), [Cu(OH-PIP)(Ala)(Cl)]·H2O (3), [Cu(OH-PIP)(Met)]PF6·2H2O (4), and [Cu(OH-PIP)(Gln)(H2O)](Cl)·3H2O (5) have been synthesized and characterized by infrared spectroscopy, elemental analysis, and single crystal X-ray diffraction analysis. X-ray crystallography indicates that all Cu atoms are five-coordinated in a square-pyramidal configuration. The complexes have been screened for cytotoxicity against human breast cancer cell lines MCF-7, MDA-MB-231, and CAL-51. The best anticancer activity is obtained with triple-negative breast cancer CAL-51 and MDA-MB-231 cell lines, with IC50 values in the range of 0.082-0.69 μM. Importantly, the copper compounds were more effective than carboplatin at triggering cell death. Mechanistically, the complexes inhibit proteasomal chymotrypsin-like activity, and docking studies reveal their 20S proteasome binding sites. As a consequence, they cause the accumulation of ubiquitinated proteins, inhibit cell proliferation, and induce apoptosis. In addition, these copper complexes decrease the stemness of triple-negative breast cancer cells and have synergistic effects with CBP on TNBC cells, indicating their great potential as a novel therapy for triple-negative breast cancer.

Novel copper complexes as potential proteasome inhibitors for cancer treatment (Review)

The use of metal complexes in the pharmaceutical industry has recently increased and as a result, novel metal‑based complexes have initiated an interest as potential anticancer agents. Copper (Cu), which is an essential trace element in all living organisms, is important in maintaining the function of numerous proteins and enzymes. It has recently been demonstrated that Cu complexes may be used as tumor‑specific proteasome inhibitors and apoptosis inducers, by targeting the ubiquitin‑proteasome pathway (UPP). Cu complexes have demonstrated promising results in preclinical studies. The UPP is important in controlling the expression, activity and location of various proteins. Therefore, selective proteasome inhibition and apoptotic induction in cancer cells have been regarded as potential anticancer strategies. The present short review discusses recent progress in the development of Cu complexes, including clioquinol, dithiocarbamates and Schiff bases, as proteasome inhibitors for cancer treatment. A discussion of recent research regarding the understanding of metal inhibitors based on Cu and ligand platforms is presented.

Synthesis, magnetism and spectral studies of six defective dicubane tetranuclear {M4O6} (M = NiII, CoII, ZnII) and three trinuclear CdII complexes with polydentate Schiff base ligands

Six defective dicubane face-shared and three trinuclear complexes are synthesized. The magnetic behaviors of Ni^II/Co^II complexes and fluorescence properties of Zn^II and Cd^II are studied.