New Ionic Cu(II) and Co(II) DACH–Flufenamate Conjugate Complexes: Spectroscopic Characterization, Single X–Ray Studies and Cytotoxic Activity on Human Cancer Cell Lines

Fenamates: Forgotten treasure for cancer treatment and prevention: Mechanisms of action, structural modification, and bright future

Fenamates as classical nonsteroidal anti-inflammatory agents are widely used for relieving pain. Preclinical studies and epidemiological data highlight their chemo-preventive and chemotherapeutic potential for cancer. However, comprehensive reviews of fenamates in cancer are limited. To accelerate the repurposing of fenamates, this review summarizes the results of fenamates alone or in combination with existing chemotherapeutic agents. This paper also explores targets of fenamates in cancer therapy, including COX, AKR family, AR, gap junction, FTO, TEAD, DHODH, TAS2R14, ion channels, and DNA. Besides, this paper discusses other mechanisms, such as regulating Wnt/β-catenin, TGF-β, p38 MAPK, and NF-κB pathway, and the regulation of the expressions of Sp, EGR-1, NAG-1, ATF-3, ErbB2, AR, as well as the modulation of the tumor immune microenvironment. Furthermore, this paper outlined the structural modifications of fenamates, highlighting their potential as promising leads for anticancer drugs.

Structural insights into interactions of new polymeric (μ-oxo) bridged Cu(II) complexes of taurine with yeast tRNA by spectroscopic and computational approaches and its application towards chemoresistant cancer lines

RNA-targeted drugs are considered as safe treatment option for the cure of many chronic diseases preventing off-targeted delivery and acute toxic manifestations. FDA has approved many such RNA therapies in different phases of clinical trials, validating their use for the treatment of various chronic diseases. We report herein, new water-soluble (μ-oxo) bridged polymeric Cu(II) complexes of taurine (2-aminoethane sulfonic acid) complexes 1 and 2. The therapeutic potency of 1 and 2 was ascertained by studying biophysical interactions with tRNA/ct-DNA. The experimental results demonstrated that the complexes interacted avidly to nucleic acids through intercalation mode depicting a specific preference for tRNA in comparison to ct-DNA and, moreover 2 showed higher binding propensity than 1. The electrophoretic behaviour of the complexes with plasmid pBR322 DNA and tRNA were examined by gel mobility assay that revealed a concentration-dependent activity with complex 2 performing more efficient cleavage as compared to complex 1. Cytotoxicity results on cancer cell strains displayed higher cytotoxicity than complex 1 against treated cancer cells. The synthesized copper(II) taurine complexes have met the basic criteria of anticancer drug design as they are structurally well-characterized, exhibiting good solubility in water, lipophilic in nature with superior intercalating propensity towards tRNA and cytotoxic in nature.

Structural and Biological Properties of Heteroligand Copper Complexes with Diethylnicotinamide and Various Fenamates: Preparation, Structure, Spectral Properties and Hirshfeld Surface Analysis

Herein, we discuss the synthesis, structural and spectroscopic characterization, and biological activity of five heteroligand copper(II) complexes with diethylnicotinamide and various fenamates, as follows: flufenamate (fluf), niflumate (nifl), tolfenamate (tolf), clonixinate (clon), mefenamate (mef) and N, N-diethylnicotinamide (dena). The complexes of composition: [Cu(fluf)2(dena)2(H2O)2] (1), [Cu(nifl)2(dena)2] (2), [Cu(tolf)2(dena)2(H2O)2] (3), [Cu(clon)2(dena)2] (4) and [Cu(mef)2(dena)2(H2O)2] (5), were synthesized, structurally (single-crystal X-ray diffraction) and spectroscopically characterized (IR, EA, UV-Vis and EPR). The studied complexes are monomeric, forming a distorted tetragonal bipyramidal stereochemistry around the central copper ion. The crystal structures of all five complexes were determined and refined with an aspheric model using the Hirshfeld atom refinement method. Hirshfeld surface analysis and fingerprint plots were used to investigate the intermolecular interactions in the crystalline state. The redox properties of the complexes were studied and evaluated via cyclic voltammetry. The complexes exhibited good superoxide scavenging activity as determined by an NBT assay along with a copper-based redox-cycling mechanism, resulting in the formation of ROS, which, in turn, predisposed the studied complexes for their anticancer activity. The ability of complexes 1–4 to interact with calf thymus DNA was investigated using absorption titrations, viscosity measurements and an ethidium-bromide-displacement-fluorescence-based method, suggesting mainly the intercalative binding of the complexes to DNA. The affinity of complexes 1–4 for bovine serum albumin was determined via fluorescence emission spectroscopy and was quantitatively characterized with the corresponding binding constants. The cytotoxic properties of complexes 1–4 were studied using the cancer cell lines A549, MCF-7 and U-118MG, as well as healthy MRC-5 cells. Complex 4 exhibited moderate anticancer activity on the MCF-7 cancer cells with IC50 = 57 μM.

Progress of Metal-Based Anticancer Chemotherapeutic Agents in Last two Decades and their Comprehensive Biological (DNA/RNA Binding, Cleavage and Cytotoxicity Activity) Studies

During last two decades, there has been an enormous growth in the discovery of innovative active inorganic anticancer complexes (exerting remarkable cytotoxicity at sub micro-molar levels) derived from myriad ligand scaffolds, mainly acting on cancerous vs healthy cells by either halting or inhibiting their uncontrolled growth. The phenomenal success of cisplatin to treat numerous forms of solid malignancies has placed metal-based drugs to the forefront of treatment strategies against cancers. More than 10,000 platinum anticancer complexes have been developed during the past 40 years, but only five drugs have been approved for usage in humans while ten more complexes are currently undergoing clinical trials. Most of the compounds have failed either at R&D stages or in preclinical trails. This has led to extensive investigations by researchers of medicinal chemistry, including our group to design and prepare tailored 3d-metallo-drugs and organotin(IV) compounds from some naturally occurring bioactive compounds, such as amino-acids, peptides, chromone derivatives and NSAID's etc. that were used either alone or in cocktail combination, capable of specifically targeting DNA, lnc RNAs and proteins. Furthermore, 3d-metal ions such as copper, cobalt and zinc etc. incorporated in these ligand framework are biocompatible and induce a unique multi-modal mechanism of cytotoxic action involving angiogenesis, ROS-induced DNA damage, apoptosis by p53 mitochondrial genes and caspases etc. The results observed a positive correlation between the binding affinity of complexes with DNA (as quantified by intrinsic binding constant values) and their cytotoxic behavior. Complexes with high DNA binding propensity were typically lethal against a diverse panel of malignant cell types compared to normal cells.

Advances in anticancer alkaloid-derived metallo-chemotherapeutic agents in the last decade: Mechanism of action and future prospects

Metal-based complexes have occupied a pioneering niche in the treatment of many chronic diseases, including various types of cancers. Despite the phenomenal success of cisplatin for the treatment of many solid malignancies, a limited number of metallo-drugs are in clinical use against cancer chemotherapy till date. While many other prominent platinum and non‑platinum- based metallo-drugs (e.g. NAMI-A, KP1019, carboplatin, oxaliplatin, titanocene dichloride, casiopeinas® etc) have entered clinical trials, many have failed at later stages of R&D due to deleterious toxic effects, intrinsic resistance and poor pharmacokinetic response and low therapeutic efficacy. Nonetheless, research in the area of medicinal inorganic chemistry has been increasing exponentially over the years, employing novel target based drug design strategies aimed at improving pharmacological outcomes and at the same time mitigating the side-effects of these drug entities. Over the last few decades, natural products became one of the key structural motifs in the anticancer drug development. Many eminent researchers in the area of medicinal chemistry are devoted to develop new 3d-transition metal-based anticancer drugs/repurpose the existing bioactive compounds derived from myriad pharmacophores such as coumarins, flavonoids, chromones, alkaloids etc. Metal complexes of natural alkaloids and their analogs such as luotonin A, jatrorrhizine, berberine, oxoaporphine, 8-oxychinoline etc. have gained prominence in the anticancer drug development process as the naturally occurring alkaloids can be anti-proliferative, induce apoptosis and exhibit inhibition of angiogenesis with better healing effect. While some of them are inhibitors of ERK signal-regulated kinases, others show activity based on cyclooxygenases-2 (COX-2) and telomerase inhibition. However, the targets of these alkaloid complexes are still unclear, though it is well-established that they demonstrate anticancer potency by interfering with multiple pathways of tumorigenesis and tumor progression both in vitro and in vivo. Over the last decade, many significant advances have been made towards the development of natural alkaloid-based metallo-drug therapeutics for intervention in cancer chemotherapy that have been summarized below and reviewed in this article.

Biophysical binding profile with ct-DNA and cytotoxic studies of a modulated nanoconjugate of umbelliferone cobalt oxide loaded on graphene oxide (GO) as drug carrier

In an attempt to identify suitable nano-carriers for drug delivery, natural drug umbelliferone was chosen to synthesize new modulated nanoconjugate of umbelliferone cobalt oxide with cobalt (II) nitrate in one pot assembly in the presence of tannic acid. The synthesized nanoconjugate drug (NCD) was then loaded on graphene oxide (GO) as drug carrier by simple ultrasonication method and thoroughly characterized by various spectroscopic techniques (FT-IR, SEM, TEM, XRD, EPR and thermogravimetric analysis) which revealed the successful loading of the nanoconjugate drug on GO. The UV-visible, fluorescence and electrochemical studies suggested that strong π-π stacking interactions exist between nanoconjugate drug and GO. The binding studies of NCD-GO with ct-DNA were performed by various optical and biophysical methods viz., UV-visible, fluorescence, circular dichroism (CD) and cyclic voltammetry (CV) which indicated electrostatic mode of binding towards the ct-DNA. Furthermore, condensate of nanoconjugate drug-loaded GO (NCD-GO) with ct-DNA was prepared and analyzed by scanning electron microscopy (SEM) which revealed that the interaction of NCD-GO with ct-DNA had occurred. Cleavage activity of NCD-GO with pBR322 was evaluated by gel electrophoresis and it was found that NCD-GO cleave DNA through hydrolytic pathway involving hydroxyl radical (OH). The cytotoxicity of NCD-GO was evaluated against human liver carcinoma (Huh-7), prostate cancer (Du-145) cell lines along with normal cell line (PNT 2). The results obtained showed selective cytotoxic activity of NCD-GO against Du-145 cell lines. The intracellular uptake was visualized by confocal microscopy which revealed the significant cellular uptake and internalization of nanoparticles by cells. Moreover, the adsorption of cobalt oxide umbelliferone on GO was studied by density functional theory. The process of adsorption was found exothermic in nature and the optimized geometry structure is quite stable. Communicated by Ramaswamy H. Sarma.

Water soluble ionic Co(II), Cu(II) and Zn(II) diimine-glycinate complexes targeted to tRNA: structural description, in vitro comparative binding, cleavage and cytotoxic studies towards chemoresistant prostate cancer cells

Four new water soluble Co(ii), Cu(ii) and Zn(ii) ionic metal complexes (1-4) [Cu(diimine)(H2O)2(glycinate)]+[glycinate]-, [Co(diimine)(H2O)4]+[glycinate]- and [Zn(diimine) (H2O)4]+[glycinate]-, where diimine = 2,2'-bipyridine (1-3) and 1,10-phenanthroline (4) were synthesized and thoroughly characterized by spectroscopic and single X-ray crystallographic studies. Complex 1 possesses a triclinic crystal system with a penta-coordinated geometry whereas complexes 2-4 crystallized in an isostructural monoclinic system having distorted octahedral geometry. Density functional theory (DFT) studies for complexes 1-4 were performed to correlate their geometrical parameters and to calculate the energy of frontier molecular orbitals. The corroborative results of spectroscopic and voltammetric studies with ct-DNA and tRNA revealed that the complexes bind noncovalently via an electrostatic mode of binding with specificity for tRNA as compared to ct-DNA. Gel electrophoresis experiments revealed that all the complexes unwind the plasmid pBR322 DNA at low micromolar concentrations (2-9 μM) following an oxidative mechanism for Cu(ii) and Co(ii) complexes (1, 2 and 4) whereas the Zn(ii) complex (3) mediates DNA cleavage by the hydrolytic pathway. The tRNA cleavage showed concentration and time dependent activity of the complexes to promote RNA hydrolysis. Furthermore, the BSA binding ability of complexes 1-4 was monitored, which revealed that the complexes could quench the intrinsic fluorescence in a static manner. Complexes 1-4 were found to be non-toxic towards normal prostate epithelial cells, PNT2, but were potent against chemoresistant metastatic prostate cancer cells, Du145, with GI50 values ranging from 12.75-37 μM. Complexes 1 and 2 also showed cytotoxic activity against cancer stem cells having GI50 values of 14.70 and 14.90 μM, respectively. Molecular docking studies were performed with DNA and tRNA which further validated the spectroscopic analysis demonstrating the higher binding affinity of the complexes towards tRNA.

Evaluation of cytotoxic potential of structurally well-characterized RNA targeted ionic non-steroidal anti-inflammatory (NSAID) Cu(ii) & Zn(ii) DACH–mefenamato drug conjugates against human cancer cell lines

New RNA targeted ionic [Cu(DACH)₂(H₂O)₂](mef)₂, 1 and [Zn(DACH)₂(H₂O)₂](mef)₂, 2 drug conjugates were synthesized and characterized by spectroscopic techniques FT-IR, UV-vis, EPR in case of 1 and ¹H and ¹³C NMR in case of 2, ESI-MS, thermogravimetric analysis and single-crystal X-ray structure determination in case of 1. The interaction studies of 1 & 2 with most likely drug targets like ctDNA and tRNA were performed which demonstrated that the complexes 1 and 2 exhibited strong preferential binding to tRNA as compared to ctDNA, K_b = 2.52(±0.04) × 10⁵ M⁻¹, 7.85(±0.02) × 10⁴ M⁻¹, respectively. Scanning electron microscopy analyses of complex-ctDNA/tRNA condensates suggested the interaction of complexes with ctDNA/tRNA had occurred, followed by lengthening of DNA double helix and bulge region of tRNA. Cytotoxic activity of 1 and 2 against human cancer cell lines namely; MCF-7 (breast), HeLa (cervical), MIA-PA-CA 2 (pancreatic), A-498 (kidney), Hep-G2 (hepatoma) was evaluated by SRB assay. The obtained results showed that copper complex 1 was an outstanding cytotoxic agent with remarkably good GI₅₀ value (<10 μg ml⁻¹) against the tested cancer cell lines except for MIA-PA-CA 2, while zinc complex 2 revealed moderate cytotoxicity against all the tested cancer cell lines.

New RNA targeted ionic NSAID drug conjugates were evaluated for their antiproliferative activity against human cancer cell lines.