Zn(II) Curcuminate Complexes with 2,2'-bipyridine and Carboxylates

Density Functional Theory-Guided Photo-Triggered Anticancer Activity of Curcumin-Based Zinc(II) Complexes

Photodynamic therapy (PDT) has evolved as a new therapeutic modality for cancer treatment with fewer side effects and drug resistance. Curcumin exhibits PDT activity, but its low bioavailability restricts its clinical application. Here, the bioavailability of curcumin was increased by its complex formation with the Zn(II) center. For a structure-activity relationship study, Zn(II)-based complexes (1-3) comprising N^N-based ligands (2,2'-bipyridine in 1 and 2 or 1,10-phenanthroline in 3) and O^O-based ligands (acetylacetone in 1, monoanionic curcumin in 2 and 3) were synthesized and thoroughly characterized. The X-ray structure of the control complex, 1, indicated a square pyramidal shape of the molecules. Photophysical and TD-DFT studies indicated the potential of 2 and 3 as good visible light type-II photosensitizers for PDT. Guided by the TD-DFT studies, the low-energy visible light-triggered singlet oxygen (1O2) generation efficacy of 2 and 3 was explored in solution and in cancer cells. As predicted by the TD-DFT calculations, these complexes produced 1O2 efficiently in the cytosol of MCF-7 cancer cells and ultimately displayed excellent apoptotic anticancer activity in the presence of light. Moreover, the molecular docking investigation showed that complexes 2 and 3 have very good binding affinities with caspase-9 and p-53 proteins and could activate them for cellular apoptosis. Further molecular dynamics simulations confirmed the stability of 3 in the caspase-9 protein binding site.

A moderate intensity ligand works best: a theoretical study on passivation effects of pyridine-based molecules for perovskite solar cells

Improving battery stability while maintaining high photoelectric conversion efficiency remains the bottleneck in the current development of perovskite solar cells (PSCs). Three π-conjugated pyridine-based molecules, pyridine (Py), bipyridine (Bpy), and terpyridine (Tpy), were adopted to passivate the PSCs in recent experiments (J. Chen, S.-G. Kim, X. Ren, H. S. Jung and N.-G. Park, J. Mater. Chem. A, 2019, 7, 4977-4987; J. Zhang, J. Duan, Q. Zhang, Q. Guo, F. Yan, X. Yang, Y. Duan and Q. Tang, Chem. Eng. J., 2022, 431, 134230), in which Bpy works best in terms of photovoltaic properties and moisture tolerance. In this work, based on density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations, we demonstrate that Bpy displays the least structural fluctuation when adsorbed on the perovskite surface, enlarges the bandgap suppressing electron-hole recombination, and exhibits remarkable shielding effects against moisture. The appropriate anchoring ability of Bpy retains robust binding strength and preferable charge transfer ability compared to Py at the interfaces between the passivation molecules (PMs) and MAPbI₃. In contrast, although Tpy possesses the strongest charge-transfer capability, it introduces midgap states owing to intense electronegativity, providing additional pathways for nonradiative charge relaxation. Besides, Tpy triggers rapid diffusions of water and larger atomic fluctuations, destroying the structures of the perovskite through the removal of lead atoms. Our computational results not only rationalize the experimental observations but also provide valuable guidance at the atomic level to design novel PMs that endow PSCs with outstanding photovoltaic performance as well as stability against moisture.

An insight into the mixed quantum mechanical-molecular dynamic simulation of a ZnII-Curcumin complex with a chosen DNA sequence that supports experimental DNA binding investigations

An important aspect of research pertaining to Curcumin (HCur) is the need to arrest its degradation in aqueous solution and in biological milieu. This may be achieved through complex formation with metal ions. For this reason, a complex of HCur was prepared with Zn^II, that is not likely to be active in redox pathways, minimizing further complications. The complex is monomeric, tetrahedral, with one HCur, an acetate and a molecule of water bound to Zn^II. It arrests degradation of HCur to a considerable extent that was realized by taking it in phosphate buffer and in biological milieu. The structure was obtained by DFT calculations. Stable adduct formation was identified between optimized structures of HCur and [Zn(Cur)] with DNA (PDB ID: 1BNA) through experiments validated with multiscale modeling approach. Molecular docking studies provide 2D and 3D representations of binding of HCur and [Zn(Cur)] through different non-covalent interactions with the nucleotides of the chosen DNA. Through molecular dynamics simulation, a detailed understanding of binding pattern and key structural characteristics of the generated DNA-complex was obtained following analysis by RMSD, RMSF, radius of gyration, SASA and aspects like formation of hydrogen bonds. Experimental studies provide binding constants for [Zn(Cur)] with calf thymus DNA at 25 °C that effectively helps one to realize its high affinity towards DNA. In the absence of an experimental binding study of HCur with DNA, owing to its tendency to degrade in solution, a theoretical analysis of the binding of HCur to DNA is extremely helpful. Besides, both experimental and simulated binding of [Zn(Cur)] to DNA may be considered as a case of pseudo-binding of HCur to DNA. In a way, such studies on interaction with DNA helps one to identify HCur's affinity for cellular target DNA, not realized through experiments. The entire investigation is an understanding of experimental and theoretical approaches that has been compared continuously, being particularly useful when a molecule's interaction with a biological target cannot realized experimentally.

Copper-Curcumin-Bipyridine Dicarboxylate Complexes as Anticancer Candidates

In this study, copper complexes with Curcumin (Cur) and 2,2'-bipyridine-5,5'-dicarboxylic acid (BPYD) were synthesized and their cytotoxicity on the MDA-MB-231 cell lines was evaluated. The resulting complex was characterized using FTIR, UV/VIS, CHNS, TGA, ICP-MS, and Mass spectroscopy techniques. The in-vitro cytotoxicity was studied on the MDA-MB-231 as a cancerous cell line and the HUVEC as a normal cell line. Reactive oxygen species (ROS) production was measured using the 2',7'-dichlorofluorescein diacetate (DCFDA) test in the MDA-MB-231 cancer cell lines. The in-vitro assays revealed that all synthesized copper complexes exhibited a higher cytotoxicity effect than carboplatin as a positive control on the MDA-MB-231 cells. While the synthesized complexes exhibited cytotoxic effects on cancerous cell lines, they are practically safe on normal cells. The Cu-Cur-BPYD complexes (a5 & b5) exhibited higher cytotoxicity on MDA-MB-231 cells with IC₅₀ s around 4.9 and 2.3 mM, respectively. It can be concluded that the synthesized Cu-Cur-BPYD complexes (a5 & b5) could be considered effective anticancer candidates in complementary studies.

Zinc curcumin complex on fluoride doped hydroxyapatite with enhanced biological properties for dental and orthopedic applications

Since antiquity, curcumin, from turmeric is utilized in traditional Indian medicine (Ayurveda) to treat bone disorders. However, the hydrophobic nature and poor absorption of curcumin limit its clinical applications. There is a need to develop a novel strategy that can significantly enhance curcumin's biological properties. The current work reports the utilization of Zn²⁺-curcumin complex from a fluoride doped hydroxyapatite matrix for osteosarcoma inhibition, osteoblast growth, and anti-bacterial properties. The interaction between Zn²⁺ and curcumin increases curcumin release by ~ 2.5 folds. The fabricated drug delivery system shows up to ~ 1.6 times enhancement in osteoblast cell viability. The presence of curcumin results in ~ 4 times more osteosarcoma inhibition compared to control. The antibacterial efficacy of this system is confirmed against Staphylococcus aureus, due to the presence of antibacterial fluoride, zinc, and curcumin. This multifunctional drug delivery system can be utilized for various bone-tissue engineering and dental applications.

The role of folic acid in inducing of apoptosis by zinc(II) complex in ovary and cervix cancer cells

Herein, the synthesis, structure, binding affinity, cytotoxicity, and apoptotic properties of the new Zn(II) complex composed of folic acid and bipyridine ligands are reported. Because folic acid has the ability to target cancer cells directly, so it can play a role in targeted drug delivery of the complex and be useful to distinguish normal cells from cancerous. After characterization of Zinc complex utilizing FTIR, EA, and NMR, the results of MTT assay were shown that viability levels of two FR-positive cell lines (HeLa and Ovcar-3) are dependent on time and concentration of [Zn(bpy)FA], whereas, did not show a significant effect on FR-negative cell lines (A549). Also, Real-time PCR revealed that the presence of FA can influence the expression of apoptosis in cervical carcinoma HeLa cells while cisplatin alone doesn't have the ability to trigger apoptosis. Furthermore, the experimental results were evaluated using pharmacophore modeling and molecular docking analysis. Finally, the stability of the Zn(II) complex was surveyed using quantum mechanical studies.

Metal-Curcumin Complexes in Therapeutics: An Approach to Enhance Pharmacological Effects of Curcumin

Curcumin, an active component of the rhizome turmeric, has gained much attention as a plant-based compound with pleiotropic pharmacological properties. It possesses anti-inflammatory, antioxidant, hypoglycemic, antimicrobial, neuroprotective, and immunomodulatory activities. However, the health-promoting utility of curcumin is constrained due to its hydrophobic nature, water insolubility, poor bioavailability, rapid metabolism, and systemic elimination. Therefore, an innovative stride was taken, and complexes of metals with curcumin have been synthesized. Curcumin usually reacts with metals through the β-diketone moiety to generate metal–curcumin complexes. It is well established that curcumin strongly chelates several metal ions, including boron, cobalt, copper, gallium, gadolinium, gold, lanthanum, manganese, nickel, iron, palladium, platinum, ruthenium, silver, vanadium, and zinc. In this review, the pharmacological, chemopreventive, and therapeutic activities of metal–curcumin complexes are discussed. Metal–curcumin complexes increase the solubility, cellular uptake, and bioavailability and improve the antioxidant, anti-inflammatory, antimicrobial, and antiviral effects of curcumin. Metal–curcumin complexes have also demonstrated efficacy against various chronic diseases, including cancer, arthritis, osteoporosis, and neurological disorders such as Alzheimer’s disease. These biological activities of metal–curcumin complexes were associated with the modulation of inflammatory mediators, transcription factors, protein kinases, antiapoptotic proteins, lipid peroxidation, and antioxidant enzymes. In addition, metal–curcumin complexes have shown usefulness in biological imaging and radioimaging. The future use of metal–curcumin complexes may represent a new approach in the prevention and treatment of chronic diseases.

Synthesis of the Bacteriostatic Poly(l-Lactide) by Using Zinc (II)[(acac)(L)H2O] (L = Aminoacid-Based Chelate Ligands) as an Effective ROP Initiator

The paper presents a synthesis of poly(l-lactide) with bacteriostatic properties. This polymer was obtained by ring-opening polymerization of the lactide initiated by selected low-toxic zinc complexes, Zn[(acac)(L)H₂O], where L represents N-(pyridin-4-ylmethylene) tryptophan or N-(2-pyridin-4-ylethylidene) phenylalanine. These complexes were obtained by reaction of Zn[(acac)₂ H₂O] and Schiff bases, the products of the condensation of amino acids and 4-pyridinecarboxaldehyde. The composition, structure, and geometry of the synthesized complexes were determined by NMR and FTIR spectroscopy, elemental analysis, and molecular modeling. Both complexes showed the geometry of a distorted trigonal bipyramid. The antibacterial and antifungal activities of both complexes were found to be much stronger than those of the primary Schiff bases. The present study showed a higher efficiency of polymerization when initiated by the obtained zinc complexes than when initiated by the zinc(II) acetylacetonate complex. The synthesized polylactide showed antibacterial properties, especially the product obtained by polymerization initiated by a zinc(II) complex with a ligand based on l-phenylalanine. The polylactide showed a particularly strong antimicrobial effect against Pseudomonas aeruginosa, Staphylococcus aureus, and Aspergillus brasiliensis. At the same time, this polymer does not exhibit fibroblast cytotoxicity.

Synthesis, physicochemical characterization and biological properties of two novel Cu(II) complexes based on natural products curcumin and quercetin

Curcumin and quercetin are two of the most prominent natural polyphenols with a diverse spectrum of beneficial properties, including antioxidant, anti-inflammatory, chemopreventive and chemotherapeutic activity. The complexation of these natural products with bioactive transition metal ions can lead to the generation of novel metallodrugs with enhanced biochemical and pharmacological activities. Within this framework, the synthesis and detailed structural and physicochemical characterization of two novel complex assemblies of Cu(II) with curcumin and quercetin and the ancillary aromatic chelator 2,2'-bipyridine is presented. The two complexes represent the only crystallographically characterized structures with Cu(II) as the central metal ion and curcumin or quercetin as the ligands. The new complexes were biologically evaluated in vitro for their antioxidant potential, both exhibiting strong scavenging activity in the 2,2-diphenyl-1-picrylhydrazyl assay, and their plasmid DNA binding/cleavage properties. Both complexes appear to be non-toxic in the eukaryotic experimental model Saccharomyces cerevisiae and merit further investigation of their pharmacological profile.

Structural Insights into Influence of Isomerism on Properties of Open Shell Cobalt Coordination System

The two coordination compounds of cobalt were designed and synthesized. The substrates were carefully selected to allow gentle tuning of the molecular structure of the designed compounds. The crystal, molecular and supramolecular structure of studied compounds has been determined and discussed. The spectroscopic and thermal properties of designed coordination compounds have been studied and their application as precursors for the synthesis of cobalt oxide nanoparticles has been demonstrated. It was proven that not only are parameters of conversion of the precursor to nanoparticles important, but also small changes in molecular structure can considerably affect the size of formed particles. For unambiguous determination of the influence of compounds structure on their UV-Vis radiation absorption, density functional theory and time-dependent density functions theory calculations have been performed. The complexity of the correct ab-initio reflection of the open shell molecular system was outlined and discussed. The results obtained from density functional theory (DFT) calculations have been also employed for discussion of the bonding properties.