Decavanadate and metformin-decavanadate effects in human melanoma cells

One-pot synthesis, structural investigation, antitumor activity and molecular docking approach of two decavanadate compounds

Two bases-decavanadates coordination compounds [(C6H13N4)2][Mg(H2O)6]2[O28V10].6H2O (1) and [(C7H11N2)4][Mg(H2O)6][O28V10].4H2O (2) have been synthesized and well characterized using vibrational spectroscopy (infrared), UV-Visible analysis and single crystal X-ray diffraction technique. The formula unit, for both compounds, is composed by the decavanadate [V10O28]6-, hydrated magnesium ion, a counter anion and free water molecules. The transition metal adopts octahedral geometries in both compound (1) and (2). The existence of a multitude of hydrogen bonding interactions for both compounds provides a stable three-dimensional supramolecular structure. Optical absorption reveals a band gap energy indicating the semi-conductive nature of the compound. In this study, the cytotoxic and the anti-proliferative activities of compounds (1) and (2) on human cancer cells (U87 and MDA-MB-231) were investigated. Both compounds demonstrated dose-dependent anti-proliferative activity on U87 and MDA-MB-231 with respective IC50 values of 0.82 and 0.31 μM and 1.4 and 1.75 μM. These data provide evidence on the potential anticancer activity of [(C6H13N4)2][Mg(H2O)6]2[O28V10].6H2O and [(C7H11N2)4][Mg(H2O)2][O28V10].4H2O. Molecular docking of the compounds was also examined. Molecular docking studies were performed for both compounds against four target receptors and revealed better binding affinity with these targets in comparison to Cisplatin. Moreover, molecular docking investigations suggest that these compounds may function as potential inhibitors of proteins in brain and breast cells, exhibiting greater efficiency compared to Cisplatin.

Emerging Topics in Metal Complexes: Pharmacological Activity

This Special Issue (SI), "Emerging Topics in Metal Complexes: Pharmacological Activity", includes reports updating our knowledge on metals with multidirectional biological properties and metal-containing compounds/complexes for their potential therapeutic applications, with a focus on strategies improving their pharmacological features [...].

Repurposing Therapeutic Drugs Complexed to Vanadium in Cancer

Repurposing drugs by uncovering new indications for approved drugs accelerates the process of establishing new treatments and reduces the high costs of drug discovery and development. Metal complexes with clinically approved drugs allow further opportunities in cancer therapy-many vanadium compounds have previously shown antitumor effects, which makes vanadium a suitable metal to complex with therapeutic drugs, potentially improving their efficacy in cancer treatment. In this review, covering the last 25 years of research in the field, we identified non-oncology-approved drugs suitable as ligands to obtain different vanadium complexes. Metformin-decavanadate, vanadium-bisphosphonates, vanadyl(IV) complexes with non-steroidal anti-inflammatory drugs, and cetirizine and imidazole-based oxidovanadium(IV) complexes, each has a parent drug known to have different medicinal properties and therapeutic indications, and all showed potential as novel anticancer treatments. Nevertheless, the precise mechanisms of action for these vanadium compounds against cancer are still not fully understood.

Decavanadate-Bearing Guanidine Derivatives Developed as Antimicrobial and Antitumor Species

To obtain biologically active species, a series of decavanadates (Hpbg)4[H2V10O28]·6H2O (1) (Htbg)4[H2V10O28]·6H2O; (2) (Hgnd)2(Hgnu)4[V10O28]; (3) (Hgnu)6[V10O28]·2H2O; and (4) (pbg = 1-phenyl biguanide, tbg = 1-(o-tolyl)biguanide, gnd = guanidine, and gnu = guanylurea) were synthesized and characterized by several spectroscopic techniques (IR, UV-Vis, and EPR) as well as by single crystal X-ray diffraction. Compound (1) crystallizes in space group P-1 while (3) and (4) adopt the same centrosymmetric space group P21/n. The unusual signal identified by EPR spectroscopy was assigned to a charge-transfer π(O)→d(V) process. Both stability in solution and reactivity towards reactive oxygen species (O2- and OH·) were screened through EPR signal modification. All compounds inhibited the development of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis bacterial strains in a planktonic state at a micromolar level, the most active being compound (3). However, the experiments conducted at a minimal inhibitory concentration (MIC) indicated that the compounds do not disrupt the biofilm produced by these bacterial strains. The cytotoxicity assayed against A375 human melanoma cells and BJ human fibroblasts by testing the viability, lactate dehydrogenase, and nitric oxide levels indicated compound (1) as the most active in tumor cells.

Combined Experimental and Computational Study of V-Substituted Lindqvist Polyoxotungstate: Screening by Docking for Potential Antidiabetic Activity

In the current work, a novel vanadotungstate compound, (C6H9N2)4[V2W4O19]·2H2O (1), is isolated by a simple stepwise synthesis method and characterized by a combined experimental and computational study. Molecular docking is conducted for the first time for this kind of substituted Lindqvist polyoxometalates to elucidate for potential antidiabetic activity. Hence, the modeling results revealed a significant docking score of the reported compound to bind to the active sites of α-glucosidase with the lowest binding energy of -5.7 kcal/mol, where the standard drug acarbose (ACB) had -4.6 kcal/mol binding energy. The stability of binding was enhanced by strong H-bonding, van der Waals, and electrostatic interactions occurring in the three-dimensional (3D) supramolecular network of polyanionic vanadotungstate subunits templated with organic moieties as shown by X-ray diffraction and Hirshfeld analyses. Furthermore, density functional theory (DFT) calculations supported with photophysical measurements are also discussed to predict the most chemical and biological reactivity. In this view, the complete description of electronic and biological features of (1) is enhanced by determination of the highest occupied molecular orbital (HOMO)/least unoccupied molecular orbital (LUMO) energy, electronic density, ionization potential, electron affinity, etc. These chemical descriptors, intermolecular interactions, docking score, and binding free energy estimation are essential in understanding the reactivity of this bioactive compound offering potential inhibition of the α-glucosidase enzyme.

Speciation atlas of polyoxometalates in aqueous solutions

Speciation is the key parameter in solution chemistry that describes the composition, concentration, and oxidation state of each chemical form of an element present in a sample. The speciation study of complex polyatomic ions has remained challenging because of the large number of factors affecting stability and the limited number of direct methods. To address these challenges, we developed the speciation atlas of 10 polyoxometalates commonly used in catalytic and biological applications in aqueous solutions, where the speciation atlas provides both a species distribution database and a predictive model for other polyoxometalates to be used. Compiled for six different polyoxometalate archetypes with three types of addenda ions based on 1309 nuclear magnetic resonance spectra under 54 different conditions, the atlas has revealed a previously unknown behavior of polyoxometalates that may account for their potency as biological agents and catalysts. The atlas is intended to promote the interdisciplinary use of metal oxides in various scientific fields.

Metals and Metal Complexes in Diseases with a Focus on COVID-19: Facts and Opinions

In the present Special Issue on "Metals and Metal Complexes in Diseases with a Focus on COVID-19: Facts and Opinions", an attempt has been made to include reports updating our knowledge of elements considered to be potential candidates for therapeutic applications and certain metal-containing species, which are extensively being examined towards their potential biomedical use due to their specific physicochemical properties [...].

Biological Consequences of Vanadium Effects on Formation of Reactive Oxygen Species and Lipid Peroxidation

Lipid peroxidation (LPO), a process that affects human health, can be induced by exposure to vanadium salts and compounds. LPO is often exacerbated by oxidation stress, with some forms of vanadium providing protective effects. The LPO reaction involves the oxidation of the alkene bonds, primarily in polyunsaturated fatty acids, in a chain reaction to form radical and reactive oxygen species (ROS). LPO reactions typically affect cellular membranes through direct effects on membrane structure and function as well as impacting other cellular functions due to increases in ROS. Although LPO effects on mitochondrial function have been studied in detail, other cellular components and organelles are affected. Because vanadium salts and complexes can induce ROS formation both directly and indirectly, the study of LPO arising from increased ROS should include investigations of both processes. This is made more challenging by the range of vanadium species that exist under physiological conditions and the diverse effects of these species. Thus, complex vanadium chemistry requires speciation studies of vanadium to evaluate the direct and indirect effects of the various species that are present during vanadium exposure. Undoubtedly, speciation is important in assessing how vanadium exerts effects in biological systems and is likely the underlying cause for some of the beneficial effects reported in cancerous, diabetic, neurodegenerative conditions and other diseased tissues impacted by LPO processes. Speciation of vanadium, together with investigations of ROS and LPO, should be considered in future biological studies evaluating vanadium effects on the formation of ROS and on LPO in cells, tissues, and organisms as discussed in this review.

Polyoxometalates Impact as Anticancer Agents

Polyoxometalates (POMs) are oxoanions of transition metal ions, such as V, Mo, W, Nb, and Pd, forming a variety of structures with a wide range of applications. Herein, we analyzed recent studies on the effects of polyoxometalates as anticancer agents, particularly their effects on the cell cycle. To this end, a literature search was carried out between March and June 2022, using the keywords "polyoxometalates" and "cell cycle". The effects of POMs on selected cell lines can be diverse, such as their effects in the cell cycle, protein expression, mitochondrial effects, reactive oxygen species (ROS) production, cell death and cell viability. The present study focused on cell viability and cell cycle arrest. Cell viability was analyzed by dividing the POMs into sections according to the constituent compound, namely polyoxovanadates (POVs), polyoxomolybdates (POMos), polyoxopaladates (POPds) and polyoxotungstates (POTs). When comparing and sorting the IC₅₀ values in ascending order, we obtained first POVs, then POTs, POPds and, finally, POMos. When comparing clinically approved drugs and POMs, better results of POMs in relation to drugs were observed in many cases, since the dose required to have an inhibitory concentration of 50% is 2 to 200 times less, depending on the POMs, highlighting that these compounds could become in the future an alternative to existing drugs in cancer therapy.

The crystal structure of hexalithium decavanadate hexadecahydrate, H32Li6O44V10

H32Li6O44V10, orthorhombic, Pnnm (no. 58), a = 10.3463(7) Å, b = 17.6637(14) Å, c = 9.2458(8) Å, V = 1689.7(2) Å3, Z = 2, Rgt (F) = 0.0436, wR ref (F 2) = 0.1271, T = 293 K.

Polyoxovanadate-Based Cyclomatrix Polyphosphazene Microspheres as Efficient Heterogeneous Catalysts for the Selective Oxidation and Desulfurization of Sulfides

The [V₆O₁₃]^2- cluster is successfully immobilized to the polymeric framework of cyclomatrix polyphosphazene via the facile precipitation polymerization between the phenol group symmetrically modified [V₆O₁₃]^2- and hexachlorocyclotriphosphazene. The structure of the as-prepared polyoxometalate-containing polyphosphazene (HCCP-V) was characterized by FT-IR, XPS, TGA, BET, as well as SEM and zeta potential. The presence of a rigid polyoxometalate cluster not only supports the porous structure of the polymeric framework but also provides an improved catalytic oxidation property. By using H₂O₂ as an oxidant, the as-prepared HCCP-V exhibited improved catalytic oxidation activity toward MPS, DBT, and CEES, which can achieve as high as 99% conversion. More importantly, the immobilization of POMs in the network of cyclomatrix polyphosphazene also provides better recyclability and stability of the heterogeneous catalyst.