Medicinal applications of vanadium complexes with Schiff bases

Many transition metal complexes have been explored for their therapeutic properties after the discovery of cisplatin. Schiff bases have an efficient complexation tendency with the transition metals and several medicinal properties have been reported. However, fewer studies have reported the medicinal utility of vanadium and its Schiff base complexes. This paper provides a comprehensive overview of vanadium complexes with Schiff bases along with their mechanistic insight. Vanadium complexes in + 4 and + 5 oxidation states have exhibited well-defined geometry and found to be thermodynamically stable. The studies have reported the G0/G1 phase cell cycle arrest and decreased delta psi m, inducing mitochondrial membrane depolarization in cancer cell lines along with the alterations in the metabolism of the cancer cells upon dosing with the vanadium complexes. Cancer cell invasion and growth are also found to be markedly reduced by peroxo complexes of vanadium. The studies included in the review paper have been taken from leading indexing databases and focus was laid on recent reports in literature. The biological potential of vanadium complexes of Schiff bases opens new horizons for future interdisciplinary studies and investigation focussed on understanding the biochemistry of these complexes, along with designing new complexes which have better bioavailability, solubility and low or non-toxicity.

A Co(III) Complex of 1-Amino-4-hydroxy-9,10-anthraquinone Exhibits Apoptotic Action against MCF-7 Human Breast Cancer Cells

A Co(III) complex of 1-amino-4-hydroxy-9,10-anthraquinone (QH) (Scheme-1) having the molecular formula CoQ₃ (Scheme-2) was prepared and characterized by elemental analysis, FTIR spectroscopy, UV-vis spectroscopy, fluorescence spectroscopy, and mass spectrometry. In the absence of a single crystal, the energy-optimized molecular structure of CoQ₃ was determined by employing computational methods that was validated using spectroscopic evidences, elemental analysis, and mass spectrometry data. The electrochemical properties of the complex were analyzed using cyclic voltammetry and indicate a substantial modification of the electrochemical properties of the parent amino-hydroxy-9,10-anthraquinone. CoQ₃ was thereafter tested on MCF-7 human breast cancer cells. The IC₅₀ value for a 24 h incubation was found to be (95 ± 0.05) μg/mL. The study showed that such cancer cells underwent both early and late apoptosis following the interaction with CoQ₃.

Titanium compounds containing naturally occurring dye molecules

A range of titanium compounds containing the naturally occurring dyes quinizarin (QH₂) and alizarin (AH₂) was synthesized and structurally characterized in the solid state. Among these is the first examples of a discrete metallocyclic arrangement formed exclusively using quinizarin ligands and the first examples of lanthanide containing titanium compounds of the alizarin family of ligands.

Metal Complexes of Natural Product Like-compounds with Antitumor Activity

Cancer continues to be one of the major causes of death worldwide. Despite many advances in the understanding of this complex disease, new approaches are needed to improve the efficacy of current therapeutic treatments against aggressive tumors. Natural products are one of the most consistently successful sources of drug leads. In recent decades, research activity into the clinical potential of this class of compounds in cancer has increased. Furthermore, a highly promising field is the use of metals and their complexes in the design and development of metal-based drugs for the treatment of cancer. Metal complexes offer unique opportunities due to their ability to alter pharmacology, improving the efficacy and/or reducing the negative side effects of drug molecules. In addition, transition metals as copper, iron, and manganese, among others, can interact with active sites of enzymes, playing important roles in multiple biological processes. Thus, these complexes not only possess higher activities but also reach their targets more efficiently. This review article highlights recent advances on the emerging and expanding field of metal-based drugs. The emphasis is on new therapeutic strategies consisting of metal complexes with natural product like-compounds as a starting point for the rational design of new antitumor agents.

Stabilities and Biological Activities of Vanadium Drugs: What is the Nature of the Active Species?

Diverse biological activities of vanadium(V) drugs mainly arise from their abilities to inhibit phosphatase enzymes and to alter cell signaling. Initial interest focused on anti-diabetic activities but has shifted to anti-cancer and anti-parasitic drugs. V-based anti-diabetics are pro-drugs that release active components (e.g., H₂ VO₄^- ) in biological media. By contrast, V anti-cancer drugs are generally assumed to enter cells intact; however, speciation studies indicate that nearly all drugs are likely to react in cell culture media during in vitro assays and the same would apply in vivo. The biological activities are due to V^V and/or V^IV reaction products with cell culture media, or the release of ligands (e.g., aromatic diimines, 8-hydroxyquinolines or thiosemicarbazones) that bind to essential metal ions in the media. Careful consideration of the stability and speciation of V complexes in cell culture media and in biological fluids is essential to design targeted V-based anti-cancer therapies.

High cytotoxicity of vanadium(IV) complexes with 1,10-phenanthroline and related ligands is due to decomposition in cell culture medium

Cytotoxic effects of Metvan (cis-[V^IVO(OSO₃)(Me₂phen)₂], where Me₂phen = 4,7-dimethyl-1,10-phenanthroline) and its analogues with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy) ligands in cultured human lung cancer (A549) cells have been re-investigated in conjunction with reactivity of the V(IV) complexes in neutral aerated aqueous solutions and in cell culture medium. All the V(IV) complexes underwent rapid oxidation to the corresponding V(V) species (cis-[V^V(O)₂L₂]⁺), followed by release of free ligands (shown by electrospray mass spectrometry). Decomposition of V(IV) complexes in cell culture medium within minutes at 310 K was confirmed by UV-Vis and EPR spectroscopies. High cytotoxicities (low μM or sub-μM IC₅₀ range in 72 h assays) were observed for the phen and Me₂phen complexes, but they were not different from that of the corresponding free ligands, which confirmed that the original V(IV) complexes played no significant role in the observed biological activities. The cytotoxicities of the ligands were most likely due to their complexation of redox-active essential metal ions, such as Cu(II) and Fe(II), in the medium, and their increased cellular uptake, leading to oxidative stress-related cell death. These results emphasize the need to assess the stability of metal-based drugs under the conditions of biological assays, particularly when biologically active ligands, such as 1,10-phenanthroline and its derivatives, are used. These ligands have high systemic toxicities in vivo and their release in the GI tract and blood makes the complexes unsuitable for use as anti-cancer drugs.

Two New Oxovanadium(IV) Compounds Containing Amino Acid Schiff Base and 1,10-Bathophenanthroline Ligands: Syntheses, Crystal Structures, and In Vitro Evaluation of the Anticancer Activities

Two new oxovanadium(iv) compounds containing 1,10-bathophenanthroline (Bphen) and amino Schiff base derivatives [VO(hnd-napha)(Bphen)] (1) and [VO(o-van-met)(Bphen)] (2) were synthesised (where hnd-napha and o-van-met are N-Schiff bases derived from the reaction of 2-hydroxy-1-naphthaldehyde with 3-(1-naphthyl)-l-alanine and o-vanillin with l-methionine, respectively). These compounds were characterised by elemental analysis, infrared spectroscopy, high-resolution mass spectrometry, and single-crystal X-ray diffraction (XRD). Both compounds showed low molar conductance values, indicating that they are non-electrolytes. The XRD results showed that the VIV atoms in both compounds existed in the VO3N3 coordination geometry with Schiff base and Bphen ligands. The in vitro anticancer activities of compounds 1 and 2 were evaluated against A549 human lung carcinoma and HepG2 human hepatoma cell lines using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and the results revealed that both compounds were cytotoxic with half maximal inhibitory concentration (IC50) values in the range of 8.22 ± 1.0 to 94.89 ± 3.2 μmol L−1. Notably, compound 2 exhibited much better anticancer activity in vitro against A549 cells (8.22 ± 1 μmol L−1) than [VO(acac)2] (24 ± 6 μmol L−1) or any of our previously reported oxovanadium(iv) compounds, making it comparable in activity to cisplatin (3.1 ± 0.5 μmol L−1). These results therefore suggest that compound 2 could be used as a promising lead for the development of anticancer agents for the treatment of lung cancer.

Structural and toxic effect investigation of vanadium pentoxide

A facile inorganic complex synthesis route has been developed to synthesis V2O5 nanostructures. The effects of varying incubation time on the crystallinity and morphology of the V2O5 phase has been investigated. The obtained XRD result clearly revealed the pure orthorhombic V2O5 crystalline phase. Raman antiphase bridging VO and chaining VO stretching modes peaks at 686 and 521cm(-1) attributed orthorhombic V2O5 characteristics. The V2p3/2 peak at the binding energies of 517eV and V2p1/2 peak at 524eV assigned to V(5+) oxidation state. Bioinspired V2O5 nanostructures as a biocompatible material for anticancer agents show excellent cytotoxicity at higher V2O5 concentration.

A study of DNA/BSA interaction and catalytic potential of oxidovanadium(v) complexes with ONO donor ligands

The study of DNA/BSA interaction and the catalytic potential of five mono- and dinuclear oxidoethoxido vanadium(v) complexes.