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The thermal effect of a model oxo-transfer reaction with the participation of a tungsten-containing synthetic analog of the enzyme active site, [WO2(mnt)2]2− (mnt = maleonitriledithiolate), has been determined for the first time. The value of the thermal effect indicates that the driving force of the oxo-transfer is the enthalpy factor. To determine the thermal effect of oxo-transfer, the dissolution enthalpies of the reaction participants in acetonitrile were determined: Δ H sol 0 PPh 3 = 24.9 ± 0.8 kJ mol−1, Δ H sol 0 OPPh 3 = 18.9 ± 0.6 kJ mol−1, and Δ H sol 0 ([Bu4N]2[WO2(mnt)2]) = (70.8 ± 1.9) kJ mol−1. In this study, the thermal effect of the transfer process of an oxygen atom from the tungsten complex [WO2(mnt)2]2− to the PPh3 substrate was determined at different ratios of reagents: ΔrH0 = (− 109 ± 4) kJ mol−1. The catalytic cycle of PPh3 oxidation with oxygen in the presence of [WO2(mnt)2]2− in acetonitrile solution was described calorimetrically. The absence of the reduced form of tungsten in the solution after the oxo-transfer reaction was shown spectroscopically, which confirms the role of the tungsten complex in the PPh3 oxidation as the catalyst. [ABSTRACT FROM AUTHOR]

The affinities for human albumin (HSA) of five rhodium(II) complexes of general formula [Rh2(bridge)4] (bridge = acetate, propionate, butyrate, trifluoroacetate and trifluoroacetamidate) were determined by spectrophotometry. In the case of the alkylcarboxylates, an inverse correlation of affinity with their liposolubilities was observed. Diffusion of the free or protein-bound complexes into Ehrlich cells in vitro seems to be primarily governed by the hydrophobic character of the complex. The complex [Rh2(tfc)4] exhibited affinity towards the protein (K = 214.1) as well as cell partition both in the absence (32.1%) and presence (48.6%) of HSA. The compound HSA: [Rh2(tfc)4] has had its antitumoral action in tumor-bearing Balb-c mice investigated, showing that HSA can be a drug reservoir for the rhodium complex.

Iron is a limiting nutrient for Symbiodiniaceae (colloquially known as zooxanthellae), with low solubility in seawater. The use of stable, soluble, and chemically defined iron complexes is proposed as a strategy to control the supply of this metal to target organisms. In this work, we investigated the effect of iron(II) and derivatives of iron(III) (desferrioxamine, deferiprone, deferasirox, and HBED) over the growth and metal loading of five Symbiodiniaceae species. Iron supplementation did not affect growth or metal load in species with high iron stocks. In contrast, for species with low iron stocks, hydrophobic Fe(DFX)2 was very efficient in inducing growth and iron loading. Also, the desferrioxamine derivative of iron Fe(DFO) appeared as an interesting, ecologically friendly source of the nutrient. The effect of iron supplementation on the growth of Breviolum minutum submitted to heat shock was also studied. Iron supplementation prior to the heat shock episode increased the heat tolerance of B. minutum. Such findings provide new insights for the strategy of iron supplementation to improve the fitness of Symbiodiniaceae, both in vitro and in the environment. [ABSTRACT FROM AUTHOR]

Abstract Iron chelation has already been proposed to be a feasible strategy for cancer therapeutics in that reinforced iron demand is demonstrated in cancer cells, and quite a few iron chelators have been developed for this purpose. Desferrioxamine (DFO), an iron chelator approved by the U.S. Food and Drug Administration (FDA), has been extensively examined to remove extra iron. However, DFO has been found to harbor limited efficacies in combating cancer cells due to poor cellular permeability. In the current study, we synthesized the DFO derivative, named as desferrioxamine-caffeine dimer (DFCAF) by linking DFO to caffeine with high purity and excellent stability. Our data showed that DFCAF displayed greater cellular permeability to chelate intracellular iron in 4T1 breast cancer cells than DFO, posing more inhibition on cell growth and cellular motility/invasion. Importantly, DFCAF was uncovered to remarkably deplete cancer stem cells (CSCs), as characterized by the remarkable decrease of the CD44+/high/CD24−/low and ALDH+/high subpopulation. In parallel, DFCAF was also found to greatly reverse epithelial–mesenchymal transition (EMT), suggesting the potential application to restrain tumor progression and metastasis. Collectively, these data unveiled the improved efficacy to target cancer cells and to deplete CSCs, thus opening a new path for better cancer therapeutics through iron chelation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Diflunisal forms a complex with iron(II). • Iron-diflunisal species have access to HeLa or HepG2 cells. • Increase in labile cell iron may result in oxidative stress. Abstract Drugs bearing metal-coordinating moieties can alter biological metal distribution. In this work, a complex between iron(II) and diflunisal was prepared in the solid state, exhibiting the following composition: [Fe(diflunisal) 2 (H 2 O) 2 ], (Fe(dif) 2). The ability of diflunisal to alter labile pools of both plasmatic and cellular iron was investigated in this work. We found out that diflunisal does not increase the levels of redox-active iron in plasma of iron overloaded patients. However, diflunisal efficiently carries iron into HeLa or HepG2 cells, inducing an iron-catalyzed oxidative stress. [ABSTRACT FROM AUTHOR]

Iron acquisition by bacteria and fungi involves in several cases the promiscuous usage of siderophores. Thus, antibiotic resistance from these microorganisms can be circumvented through a strategy of loading toxic metals into siderophores (Trojan Horse Effect). Desferrioxamine (dfo) and its cell-permeant derivative desferrioxamine-caffeine (dfcaf) were complexed with aluminum or gallium for this purpose. The complexes Me(dfo) and Me(dfcaf) (Me = Al 3+ and Ga 3+ ) were synthesized and characterized by mass spectroscopy and cyclic voltammetry. Their relative stabilities were studied through competitive equilibria with fluorescent probes calcein, fluorescein-desferrioxamine and 8-hydroxyquinoline. Me(dfo) and Me(dfcaf) were consistently more toxic than free Me 3+ against Escherichia coli , Pseudomonas aeruginosa , Staphylococcus aureus and Candida albicans , demonstrating the Trojan Horse Effect. Wide spectrum antimicrobial action can be obtained by loading non-essential or toxic metal ions to microbes via a convenient siderophore carrier. [ABSTRACT FROM AUTHOR]

Summary: Molecules naturally designed for the acquisition of essential metals can be used as a shuttle to deliver toxic metal ions to target organisms. In this study, we describe for the first time the synthesis of a derivative of cadmium and desferrioxamine B, a bacterial siderophore. The new compound was characterized by elemental analysis, vibrational (infrared and Raman) spectroscopy, mass coupled thermal analyses and X-ray diffraction methods. Studies on the in vitro toxicity toward a fungus and two bacterial strains indicated that the coordination compound is more active against microrganisms than cadmium chloride on a Cd-concentration basis, indicating that desferrioxamine can work as a “Trojan horse” in the delivery of a toxic metal. [ABSTRACT FROM AUTHOR]