Metal chelation Research Papers - Academia.edu (original) (raw)

2025, E-Journal of Chemistry

Copolymer resins (8-HQSABF) were synthesized by the condensation of 8-hydroxyquinoline-5-sulphonic acid and biuret with formaldehyde in the presence of hydrochloric acid as catalyst, proved to be selective chelation ion exchange copolymer resins for certain metals. Chelation ion exchange properties to these polymers were studied for Cu2+, Cd2+, Co2+and Zn2+ions. A batch equilibrium method was employed in the study of the selectivity of the distribution of a given metal ions between the polymer sample and a solution containing the metal ion. The study was carried out over a wide pH range and in a media of various ions strengths. The polymer showed a higher selectivity for Cu2+ions than for Cd2+, Co2+and Zn2+ions. Hence on the basis of above studies these copolymer may be used as semiconductors, surface coating, ion-exchangers, materials for rechargeable battery cell in various electronic industries, plastic materials, elastomers and in boiler plants

2025, Journal of agricultural and food chemistry

Pomegranate peel was separated into outer leathery skin (PS), mesocarp (PM), and divider membrane (PD), and its phenolic compounds were extracted as free (F), esterified (E), and insoluble-bound (B) forms for the first time. The total phenolic content followed the order PD > PM > PS. ABTS(•+), DPPH, and hydroxyl radical scavenging activities and metal chelation were evaluated. In addition, pomegranate peel extracts showed inhibitory effects against α-glucosidase activity, lipase activity, and cupric ion-induced LDL-cholesterol oxidation as well as peroxyl and hydroxyl radical-induced DNA scission. Seventy-nine phenolic compounds were identified using HPLC-DAD-ESI-MS(n) mainly in the form of insoluble-bound. Thirty compounds were identified for the first time. Gallic acid was the major phenolic compound in pomegranate peel, whereas kaempferol 3-O-glucoside was the major flavonoid. Moreover, ellagic acid and monogalloyl-hexoside were the major hydrolyzable tannins, whereas the d...

2025, Plasma Chemistry and Plasma Processing

We describe an atmospheric-pressure plasma process for the reduction of metal cation-containing polymer films to form electrically conductive patterns. Thin films of poly(acrylic) acid (PAA) containing silver ions (Ag ? ) were prepared by mixing the polymer with silver nitrate (AgNO 3 ) in solution to produce a cross-linked precipitate, homogenizing, and depositing onto a substrate by doctor's blade. Exposing the Ag-PAA films to a scanning microplasma resulted in reduction of the bulk dispersed Ag ? in a desired pattern at the film surface. The processed films were characterized by scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and current-voltage measurements. The resistances of the patterned features were found to depend on the thickness of the films, the microplasma scan rate, residual solvent in the film, and electric field created between the microplasma and the substrate. Together these results show that the formation of conductive features occurs via an electrodiffusion process where Ag ? diffuses from the film bulk to the surface to be reduced by the microplasma.

2024, International Journal of Molecular Sciences

Thymosin β4 (Tβ4) was extracted forty years agofrom calf thymus. Since then, it has been identified as a G-actin binding protein involved in blood clotting, tissue regeneration, angiogenesis, and anti-inflammatory processes. Tβ4 has also been implicated in tumor metastasis and neurodegeneration. However, the precise roles and mechanism(s) of action of Tβ4 in these processes remain largely unknown, with the binding of the G-actin protein being insufficient to explain these multi-actions. Here we identify for the first time the important role of Tβ4 mechanism in ferroptosis, an iron-dependent form of cell death, which leads to neurodegeneration and somehow protects cancer cells against cell death. Specifically, we demonstrate four iron 2+ and iron 3+ binding regions along the peptide and show that the presence of Tβ4 in cell growing medium inhibits erastin and glutamate-induced ferroptosis in the macrophage cell line. Moreover, Tβ4 increases the expression of oxidative stress-related genes, namely BAX, hem oxygenase-1, heat shock protein 70 and thioredoxin reductase 1, which are downregulated during ferroptosis. We state the hypothesis that Tβ4 is an endogenous iron chelator and take part in iron homeostasis in the ferroptosis process. We discuss the literature data of parallel involvement of Tβ4 and ferroptosis in different human pathologies, mainly cancer and neurodegeneration. Our findings confronted with literature data show that controlled Tβ4 release could command on/off switching of ferroptosis and may provide novel therapeutic opportunities in cancer and tissue degeneration pathologies.

2024, Biomolecules

Because of their capacity to bind metals, metal chelators are primarily employed for therapeutic purposes, but they can also find applications as colorimetric reagents and cleaning solutions as well as in soil remediation, electroplating, waste treatment, and so on. For instance, iron-chelation therapy, which is used to treat iron-overload disorders, involves removing excess iron from the blood through the use of particular molecules, like deferoxamine, that have the ability to chelate the metal. The creation of bioinspired and biodegradable chelating agents is a crucial objective that draws inspiration from natural products. In this context, starting from bioavailable molecules such as maltol and pyrogallol, new molecules have been synthetized and characterized by potentiometry, infrared spectroscopy and cyclic voltammetry. Finally, the ability of these to bind iron has been investigated, and the stability constants of ferric complexes are measured using spectrophotometry. These compounds offer intriguing scaffolds for an innovative class of versatile, multipurpose chelating agents.

2024, Biomolecules

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

2024

Emulsion is a biphasic dosage form consisting of a distributed phase covering droplets distributed uniformly within an adjacent liquid, which constitutes the continuous phase. An emulsifier is added at the interface of two immiscible liquids to stabilize thermodynamically unstable emulsion. Different types of emulsion, including water-in-oil (W/O), oil-in-water (O/W), microemulsions, and multiple emulsions, are employed for delivering specific drugs within the body. They can be used to provide nutraceuticals as a medicine delivery mechanism. In present research project the aqueous extracts of three plants i.e. Zingiber Officinal, Mentha Arvensis and Cuminum Cyminum were combined in formulation of oil-in-water emulsion. Different analytical techniques were employed to characterized the sample. The foremost parameter was to determine the organoleptic properties (color, odor and texture). Afterwards, viscosity, electrical conductivity, thermal stability, Karl Fischer titration, and pH studies indicated the stability of the formulation. The continuous phase showed no visible coalescence or sedimentation in SEM image. The infrared spectra identify the presence of secondary metabolites, PDI and AAS were the characterization procedures adapted, that reveal the sample to be free of toxic constituents. The sample was subjected to deoxyribose degradation test. We used different concentration 0.01, 0.02, 0.03 and 0.05 %. The highest potential was recorded 12.71 % at Conc. 0.05 %. It was further confirmed by antioxidant DPPH assay. Same concentrations were used for antioxidant assay. The sample emulsion shows good potential 16 and 20 % at concentration 0.10 and 0.20 %. Highest potential 27 % was observed at highest concentration 0.80 %. We also performed the metal iron chelation activity. As compared to control O/W emulsion shows 7.78 % activity at concentration 0.05 %. It was further increases with increase in concentration i.e. 17.41, 19.13 and 23.15 % at conc. 0.1, 0.2 and 0.8 %. It was found that the sample is stable and less toxic. The primary screening of the sample gives the basis for future use however, further molecular studies are needed to decode the exact biochemical mechanism of action.

2024

The bioavailability and interactive effects of calcium, iron and zinc fortified whole wheat flour chapattis on female Sprague-Dawley albino rats were determined. The whole wheat flour was fortified with CaCO 3 , FeSO 4 and ZnSO 4 at 1000, 40 and 20 mg/kg, respectively and fed to 64 female Sprague-Dawley rats for 4 weeks. Retention of Ca, Fe and Zn was determined in plasma, femur and liver tissues. Ca levels in plasma and liver did not alter significantly while the Ca retention in femur changed significantly with the change in fortificants. The calcium retention was higher in the femur of rats fed on the diet supplemented with Ca+Zn (221±13.61 mg/g) than the rats fed on the diet supplemented with Ca+Fe (219±18.92 mg/g). The iron in plasma, liver and femur ranged from 2.19±0.11 to 2.77±0.10 μg/ml, 203.5±13.24 to 251.5±17.19 μg/g and 43.5±1.05 to 52±2.07 μg/g while zinc content ranged from 1.31±0.089 to 1.55±0.114 μg/ml, 89.5±3.41 to 132± 6.10 μg/g and 175±8.29 to 191±10.85 μg/g, respectively. The minerals interacted with each other resulting in decrease of bioavailability among each other. The absorption was higher in the rats fed on fortified diet than those fed on unfortified chapatti diet. Hence, it is concluded that fortification of whole wheat flour is feasible to overcome the Ca, Fe and Zn malnutrition in the vulnerable groups.

2024, Polymer Chemistry

Detailed studies on the effect of organic conjugation length, metal centers, and metal-backbone redox interactions on the charge transport properties of conducting metallopolymers (CMPs) are reported.

2024, The Journal of Peptide Research

It acts as a signal molecule in iron metabolism and plays an important role in iron overload diseases. Recently, it has been reported that hepcidin is able to regulate the iron efflux by binding to the ferroportin protein and inducing its internalization. This activity is specific only for bioactive hepcidin-25 and not for the truncated hepcidin-20, lacking the five amino terminal residues. We have characterized the N-terminal region of the hepcidin-25 as a metal-binding site by several spectroscopic techniques and chemical studies. This region, specific for the coordination of Cu(II) and Ni(II), is known as ÔATCUN motifÕ. Moreover, we have demonstrated that the metal binding inhibits the aggregation propensity of both whole hepcidin-25 and its N-terminal fragments, probably inducing a conformational change leading to the stabilization of the N-terminal region. The identification of a metal-binding site at the N-terminus of hepcidin-25, which is necessary for its biological activity as iron-regulatory hormone, will help us to cast light both on the role of the divalent metals and of the hepcidin-25 in the iron homeostatis, and to better understand structure-function relationships of this hormonepeptide.

2024, Mikrochimica Acta

A sensitive ion-pair liquid-liquid extraction-spectrophotometric method has been developed for the determination of copper, palladium, iron and cobalt, based on the formation of metal complexes with 1-nitroso-2-naphthol-6-sulphonic acid or 2-nitroso-l-naphthol-6-sulphonic acid as primary ligand, and zephiramine as counter-ion. The coloured metal complexes obtained over different pH ranges are easily and quantitatively extracted into dichloromethane. The method has been tested with samples containing known amounts of copper, palladium, iron and cobalt in ultrapure water. The reagents provide a sensitive spectrophotometric method for determining these metals.

2024, Mikrochimica Acta

2024, European Journal of Inorganic Chemistry

The synthesis of a family of differently substituted 5-and 4,4Ј-ethynyl-bpy Pt II bisacetylide complexes (bpy = 2,2Ј-bipyridine) and their postfunctionalization using click chemistry is described. Cu I-catalyzed azide-alkyne [3+2] cycloaddition was an efficient method to decorate the Pt II complexes with a manifold of moieties in high yields. The absorption and emission properties and the electrochemical behaviour of all of the complexes have been investigated. The studied compounds emit at room temperature between 598 and 660 nm, reaching photoluminescence quantum yields of 0.33 in solution. The bright luminescent properties of the unsub

2024, European Journal of Inorganic Chemistry

2024, ACS Omega

The clinical success of Escherichia coli L-asparaginase II (EcAII) as a front line chemotherapeutic agent for acute lymphoblastic leukemia (ALL) is often compromised because of its silent inactivation by neutralizing antibodies. Timely detection of silent immune response can rely on immobilizing EcAII, to capture and detect anti-EcAII antibodies. Having recently reported the use of a portable surface plasmon resonance (SPR) sensing device to detect anti-EcAII antibodies in undiluted serum from children undergoing therapy for ALL (Aubéet al., ACS Sensors 2016, 1 (11), 1358−1365), here we investigate the impact of the quaternary structure and the mode of immobilization of EcAII onto lowfouling SPR sensor chips on the sensitivity and reproducibility of immunosensing. We show that the native tetrameric structure of EcAII, while being essential for activity, is not required for antibody recognition because monomeric EcAII is equally antigenic. By modulating the mode of immobilization, we observed that low-density surface coverage obtained upon covalent immobilization allowed each tetrameric EcAII to bind up to two antibody molecules, whereas high-density surface coverage arising from metal chelation by Nor C-terminal histidine-tag reduced the sensing efficiency to less than one antibody molecule per tetramer. Nonetheless, immobilization of EcAII by metal chelation procured up to 10-fold greater surface coverage, thus resulting in increased SPR sensitivity and allowing reliable detection of lower analyte concentrations. Importantly, only metal chelation achieved highly reproducible immobilization of EcAII, providing the sensing reproducibility that is required for plasmonic sensing in clinical samples. This report sheds light on the impact of multiple factors that need to be considered to optimize the practical applications of plasmonic sensors.

2024, Journal of Food Science and Technology

The aim of this study was to evaluate metal binding and antioxidant activities of hydrolyzed oat bran proteins followed by the determination of peptide sequences. Protamex oat bran protein hydrolysates (OBPH) were separated by reverse-phase HPLC into eight peptide fractions (F1-F8) and their abilities to either chelate metals (Fe 2? , Ca 2?) or prevent the oxidation of lipids were investigated. In the Fe 2? chelation assay, OBPH had significantly (p \ 0.05) higher activity (39.7 %) than the best performed fraction F7 (22.8 %). The second most active was F5 with 12.1 % chelating activity and this was higher than the activity of the tripeptide glutathione (5.8 %) used as control. The two most Fe 2? chelating fractions (F5, F7) however had weak calcium binding (0.6-1.0 %) properties at peptide concentration ranging from 0.2 to 1.0 mg/mL. In the lipid peroxidation assay, OBPH and all HPLC fractions prevented the oxidation of linoleic acid. More than 60 peptides mainly derived from globulin and avenin proteins were identified using tandem mass spectrometry.

2024, Food Chemistry

Peptide profiles of hydrolyzed oat proteins and the susceptibility of their polypeptides to proteolytic cleavages were determined using peptidomic analysis. In addition, antioxidant activities were also measured. Proteins isolates were first extracted with carbohydrases, Viscozyme or Cellulase and then hydrolyzed with proteases (Alcalase, Papain, Protamex, Flavourzyme). Amongst the eight hydrolysates, Viscozyme-proteins hydrolyzed with Papain showed the highest ability to quench ABTS %+ radicals (866.9 ± 10.6 µM TE/g) and to chelate ferrous ions (75 ± 0.4%) while displaying the second strongest activity for ROO % radicals (396.7 ± 14.0 µM TE/g). Peptidomics analysis showed that the higher activity of papain hydrolysate in most assays was related to its greater proteolytic action on main proteins (avenin, 11S-and 12S-globulins) compared to other proteases. In addition, the number of peptides identified in the Papain digest of proteins extracted with Viscozyme was about half relative to the number in proteins from bran treated with Cellulase and digested with the same protease. This was likely because the carbohydrases differently affected polypeptide secondary structures.

2024, Journal of Food Science and Technology

2024, Archives of Toxicology

Arsenic (As) is widely used in the modern industry, especially in the production of pesticides, herbicides, wood preservatives, and semiconductors. The sources of As such as contaminated water, air, soil, but also food, can cause serious human diseases. The complex mechanism of As toxicity in the human body is associated with the generation of free radicals and the induction of oxidative damage in the cell. One effective strategy in reducing the toxic effects of As is the usage of chelating agents, which provide the formation of inert chelator-metal complexes with their further excretion from the body. This review discusses different aspects of the use of metal chelators, alone or in combination, in the treatment of As poisoning. Consideration is given to the therapeutic effect of thiol chelators such as meso-2,3-dimercaptosuccinic acid, sodium 2,3-dimercapto-1-propanesulfonate, 2,3-dimercaptopropanol, penicillamine, ethylenediaminetetraacetic acid, and other recent agents against As toxicity. The review also considers the possible role of flavonoids, trace elements, and herbal drugs as promising natural chelating and detoxifying agents.

2024, Bulletin of the Korean Chemical Society

In this study, 5‐bromo‐2,9‐bis(5,6‐diphenyl‐1,2,4‐triazin‐3‐yl)‐1,10‐phenanthroline (5‐bromo‐Ph4‐BTPhen) was synthesized and evaluated for its ability to remove major radionuclides (Cs+, Sr2+, and Co2+). The synthesized ligand removed both Sr2+ and Co2+ from 1 mg/L aqueous solutions with extraction efficiencies of up to 99% at neutral and alkaline pH. The Sr2+ and Co2+ removal efficiencies decreased as a consequence of the higher bonding strengths of competing metal ions to the N‐donor atoms in the cavity of the ligand; competing divalent ions affected the Sr2+ and Co2+ removal efficiencies more than monovalent ions.

2024, Molecules

The binding ability of five bifunctional 3-hydroxy-4-pyridinones towards Cu2+ and Fe3+ was studied by means of potentiometric and UV–Vis spectrophotometric measurements carried out at I = 0.15 mol L−1 in NaCl(aq),T = 298.15 K and 310.15 K. The data treatments allowed us to determine speciation schemes featured by metal-ligand species with different stoichiometry and stability, owing to the various functional groups present in the 3-hydroxy-4-pyridinones structures, which could potentially participate in the metal complexation, and in the Cu2+ and Fe3+ behaviour in aqueous solution. Furthermore, the sequestering ability and metal chelating affinity of the ligands were investigated by the determination of pL0.5 and pM parameters at different pH conditions. Finally, a comparison between the Cu2+ and Fe3+/3-hydroxy-4-pyridinones data herein presented with those already reported in the literature on the interaction of Zn2+ and Al3+ with the same ligands showed that, from the thermodynami...

2024, Dalton Transactions

an tautomeric changes positively influence coordinating ability?

2024, Journal of Inorganic Biochemistry

An NMR study on the 6,6′-(2-(diethylamino)ethylazanediyl)bis(methylene) bis(5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) interaction with Al III and Zn II ions

2024, Biomolecules

2024, Polyhedron

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

2024, New Journal of Chemistry

Four kojic acid derivatives were synthesized, and their chelation properties toward Fe3+, Al3+, Cu2+, and Zn2+ metal ions were evaluated and discussed.

2024, Saudi Journal of Biological Sciences

A violet coloured complex was developed when cobalt metal reacts with ninhydrin at pH 8.2, using sodium acetate buffer solution. Absorbance of the complex was measured at 395 nm. Various factors, such as volume of the ligand used, solution pH, stability of the complex with time and interference of other metals, which effect the complex formation have been studied in detail. Present developed method can be used for the spectrophotometric estimation of cobalt with ninhydrin complex. The method is simple, selective and cheap for the determination of cobalt in very less time.

2023, New Journal of Chemistry

Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) was used to study the complexation of Cm(III) and Eu(III) in solvent extraction systems consisting of an organic phase containing TODGA (tetra-n-octyl diglycolamide) as an extracting agent and an aqueous phase containing hydrophilic complexing agents, tetrasodium salts of 2,6-bis(5,6-di(3-sulphophenyl)-1,2,4-triazin-3-yl)pyridine, SO 3-Ph-BTP 4À , or 6,6 0bis(5,6-di(3-sulphophenyl)-1,2,4-triazin-3-yl)-2,2 0-bipyridine, SO 3-Ph-BTBP 4À. Only one complex, homoleptic [Cm(TODGA) 3 ](NO 3) 3 , was found in the organic phase. No heteroleptic complexes of Cm(III) with TODGA and SO 3-Ph-BTP 4À have been detected. In contrast, in dilute aqueous HClO 4 solutions containing TEDGA (a hydrophilic homologue of TODGA) and SO 3-Ph-BTP 4À ligands, seven different Cm(III) species were identified by their distinct emission spectra. Apart from the emission bands corresponding to the hydrated Cm 3+ cation and to the complexes [Cm(SO 3-Ph-BTP)] À and [Cm(TEDGA) n ] 3+ (n = 1-3), two further emission bands were ascribed to heteroleptic complexes [Cm(TEDGA)(SO 3-Ph-BTP)] À and [Cm(TEDGA) 2 (SO 3-Ph-BTP)] À. In a similar aqueous solution containing TEDGA and SO 3-Ph-BTBP 4À , only one heteroleptic complex was identified, [Cm(TEDGA)(SO 3-Ph-BTBP)] À. In addition, quantum chemical optimisation of the structures of the postulated heteroleptic complexes was performed.

2023, The American Journal of Clinical Nutrition

Background: Random serial sampling is widely used in population pharmacokinetic studies and may have advantages compared with conventional fixed time-point evaluation of iron fortification. Objective: Our objective was to validate random serial sampling to judge the efficacy of iron fortification of a low-fat margarine. Design: We conducted a 32-wk placebo-controlled, double-blind, iron-intervention trial in 18-40-y-old Swiss women (n = 142) with serum ferritin (SF) concentrations ,25 lg/L. Women were randomly assigned to 3 groups to receive 20 g margarine, with 14 mg added iron as either micronized ground ferric pyrophosphate (MGFePP) or sodium iron edetate (NaFeEDTA), or placebo daily. We measured hemoglobin and iron status of subjects at 2 fixed time points (at baseline and the endpoint) plus 3 randomly assigned time points between 4 and 28 wk. With the use of bootstrapping, the number of observations per individual was reduced to 3 and then compared with the 5-time-point data. Mixed-effects models were used to estimate iron repletion over time for random sampling, and analysis of covariance was used for fixed time-point sampling. Results: Body iron stores increased in women who received MGFePP or NaFeEDTA compared with women who received placebo (P , 0.05). The increase in body iron stores with NaFeEDTA fortification was 2-3 times the increase with MGFePP fortification (P , 0.05); the difference was more marked in women with baseline SF concentrations ,15 lg/L (P , 0.05). Random serial sampling reduced the required sample size per group to one-tenth of that for 2 fixed time points. Compared with the 5-time-point analysis, the 3-time-point sparse sampling generated comparable estimates of efficacy. Conclusions: When used to evaluate the efficacy of iron fortificants, random serial sampling can reduce the sample size, invasiveness, and costs while increasing sensitivity. Random serial sampling more clearly describes the pattern of iron repletion and may prove useful in evaluating other micronutrient interventions.

2023, Water, Air, & Soil Pollution

In this study, N-(2-aminoethyl)salicylaldimine bonded silica gel was synthesized and characterized using Fourier transform infrared and C, H, N elemental analysis. The analytical conditions such as the pH and volume of the solution, flow rates of the sample solution and the type of eluent to achieve the simultaneous preconcentration of Cu (II), Ni(II), Cd(II) and Zn(II) were optimised using the modified silica gel loaded column using a solid phase extraction technique. Samples (50-500 ml) containing metal ions at optimal pH of 8 were passed through the column filled with the modified silica gel at 7 ml min −1 and then elution was achieved using 5 ml of 0.25 M HCl. The concentrations of metal ions in the eluates were determined using flame atomic absorption spectrometry (FAAS). The effects of matrix ions were also studied and none of the major ions interfered to the proposed method. The accuracy of the developed method was validated using a certified reference water sample (Ontario Lake water, NWTMDA-54.4). The method was successfully applied to the analysis of various natural water samples. The adsorption capacities of the modified silica gel for Cu (II), Ni(II), Cd(II) and Zn(II) ions were determined and found to be 0.332, 0.261, 0.130 and 0.375 mmol g −1 , respectively.

2023, Journal of Basic and Applied Sciences

The UV-Vis spectra, speciation diagrams, and potentiometric profiles for Cu 2+-citrate complexes in aqueous solutions are presented. As the pH increases from 2.29 to 5.15, the UV-Vis spectral profile of the Cu 2+-citrate complexes showed a blue shift from 820 nm to 760 nm. We have set the conditions to construct the speciation diagram as follow: Cu 2+ :citric acid was in 1:1 ratio with concentration of 1.0 x 10-4 mol.L-1 , 0.1023 mol.L-1 NaOH solution, and pKw = 13.781 ± 0.006 taken from Sweeton, Mesmer, and Baes. The current report is the first potentiometric study that has taken into accounts two Cu-Cit dimeric species to be refined simultaneously. These spectroscopic and potentiometric data are discussed which augment what had been reported in the literature.

2023, The Journal of Physical Chemistry A

A combined matrix isolation FTIR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the photochemistry of sulfur analogues of R-pyrone [2H-thiopyran-2-one (TP) and 2H-pyran-2-thione (PT)] was carried out. The vibrational spectra of monomers of the compounds isolated in low-temperature argon matrixes were studied experimentally and assigned completely on the basis of theoretical calculations. UV irradiation (λ > 337 nm) of the studied compounds isolated in low-temperature matrixes results mainly in the ring-opening reaction by means of the cleavage of the R-bond. Other photoprocesses, not involving the R-bond-cleavage step (such as generation of Dewar valence isomer), correspond to the minor reaction channels in both studied compounds. The ring-opening photoreaction in PT represents the first reported case of an R-bond cleavage in a compound with a CdS group attached to a six-membered ring, in which the internal strain practically does not exist, whereas the corresponding reaction in TP (a cleavage of a C-S bond in the R position with respect to a carbonyl group) is now reported for the first time. Following the ring-opening reactions, isomerization processes and intramolecular hydrogen shift reactions were observed, enabling production of TP from PT and vice versa. A detailed study of such processes was undertaken, and kinetical and mechanistical data are presented and discussed.

2023, New Journal of Chemistry

Four kojic acid derivatives were synthesized, and their chelation properties toward Fe3+, Al3+, Cu2+, and Zn2+ metal ions were evaluated and discussed.

2023, PhD Thesis

Flavour stability represents a key aspect of beer quality, but remains a major challenge for brewing science and the brewing industry. The gradual deterioration of the organoleptic qualities of beer during ageing significantly diminishes its value in several respects, including market appeal, palatability and overall drinkability. While beer is inherently unstable due to its complex composition, strategic measures can be implemented to enhance the initial freshness of the product and slow the rate of flavour deterioration. The main objective of this thesis was to address this issue by specifically targeting the detrimental effects of transition metals (iron, copper and manganese), which act as catalysts for the generation of damaging radicals through Fenton and Haber-Weiss reactions. By sequestering and subsequently removing these metal ions using chelating agents, their deleterious effects can be avoided from the mashing stage onwards. A total of nineteen chelating agents were investigated for their ability to form filterable complexes with transition metals in brewing relevant setups. These included EDTA, citric acid, tartaric acid, quercetin, chlorogenic acid, ferulic acid, gallic acid, phytic acid, tannic acid, as well as extracts derived from green tea, pomegranate, grapeseed, reishi, cinnamon, curcuma, milk thistle, ginkgo, grapefruit seed and raspberry. In the initial model study, it was revealed that a typical wort pH of 5.60 provided a more favourable environment for the removal of transition metals through complex formation than a beer pH of 4.30. Of the first nine chelators listed, tannic acid (a high molecular weight polyphenol) showed the greatest efficacy. At wort pH, it significantly removed iron and copper from solution after 0.2 µm microfiltration (-94.0 % Feᴵᴵ, -96.8 % Feᴵᴵᴵ, -98.3 % Cuᴵᴵ) compared to chelator-free controls. Other chelators also exhibited noticeable effects at pH 5.60, albeit to a lesser extent, namely quercetin (-34.6 % Feᴵᴵ, -96.2 % Feᴵᴵᴵ), gallic acid (-72.6 % Feᴵᴵᴵ, -39.9 % Cuᴵᴵ), chlorogenic acid (-90.2 % Feᴵᴵᴵ) and ferulic acid (-9.4 % Feᴵᴵ, -11.6 % Feᴵᴵᴵ). Phytic acid demonstrated an undesirable property in chelating zinc (- 70.3 % Znᴵᴵ). Despite forming complexes, EDTA, citric acid and tartaric acid did not lead to reductions in metal concentrations, as the chelates were able to pass through the microfilter. A subsequent study, evaluating the performance of all nineteen chelators in wort during laboratory-scale mashing, reaffirmed the significant impact of pH on chelator efficacy and wort metal load. Acidified mashing led to worts with higher levels of iron, manganese and zinc; with increases of 230 %, 320 % and 150 %, respectively, when the mash pH was lowered from 6.0 to 5.0. The effectiveness of tannic acid, as observed in the wort buffer solution, was confirmed in wort for iron, but not for copper. While none of the other chelators from the initial study retained their ability to substantially reduce transition metal levels in lautered wort, two novel chelating agents, green tea and pomegranate extract, were discovered among the ten alternative extracts tested in this study. In particular, pomegranate extract (containing 90 % ellagic acid) exhibited remarkable capability in decreasing iron content and suppressing radical formation in the wort. With a mash addition of 60 mg/L, it achieved approximately 80 % reductions in both variables compared to chelator-free controls. The final study investigated the effects of incorporating tannic acid, green tea and pomegranate extract into pilot scale mashes and found that all three additives were effective in reducing iron concentrations during brewing. Among the twelve trials conducted, additions of pomegranate extract again demonstrated the highest efficacy, resulting in a reduction of almost 90 % in iron level and 80 % in radical concentration in the final wort. On average, the inclusion of these chelators led to 40-60 % reduction in total post-boil aldehydes. Overall, the findings suggest that natural chelators have the potential to improve beer quality and flavour stability by reducing radical formation during brewing and lowering the concentration of transition metals and aldehydes in the final product.

2023, Physical Chemistry Chemical Physics

2023, E-Journal of Chemistry

2023, Best Practice & Research Clinical Haematology

The modern British diet contains less red meat and is lower in iron than that consumed 30 years ago. This is in spite of the fact that forti®cation of foods, particularly breakfast cereals, with iron has become more widespread. Although there is no clear relationship between dietary iron intake and iron status, isotope studies have identi®ed multiple dietary factors that in¯uence iron absorption, such as ascorbic acid, animal tissue, phytates and polyphenols. There is no evidence to suggest that current dietary changes will have a major impact on iron status in the general population; however, eects on the incidence of iron overload in individuals with HFE mutations and iron de®ciency in children and premenopausal women remain to be determined.

2023, Biomedical Journal of Scientific & Technical Research

Iron is an essential element, which is abundant in the red blood cells and plays a key role during oxidative phosphorylation in the mitochondria of all cells. The excess of iron has been indicated in several diseases as it induces oxidative stress. The present study was undertaken to understand the modulation of iron induce oxidative stress in mice by hesperidin. The mice were administered with 250 mg/kg body weight of hesperidin for five days before feeding with 5000, 10,000 and 20000 ppm FeCl3 for 30 days. The glutathione, glutathione-s-transferase, catalase, superoxide dismutase, lipid peroxidation, lactate dehydrogenase, aspartic acid transaminase, and alanine aminotransaminase levels were estimated in the liver of iron treated mice after 30 days post-iron treatment. The feeding of different concentrations of iron for 30 days led to an increase in the oxidative stress as indicated by a decline in the glutathione concentration, and glutathione-s-transferase, catalase, and superoxide dismutase activities accompanied by the rise in the lactate dehydrogenase, aspartic acid transaminase, and alanine aminotransaminase levels. Treatment of hesperidin for 5 days before iron overload elevated the activities of glutathione-s-transferase, catalase, and superoxide dismutase and glutathione concentration, whereas the activities of lactate dehydrogenase, aspartic acid transaminase, and alanine aminotransaminase and lipid peroxidation declined significantly. Our study demonstrates that pre-treatment of hesperidin for five days reduced the iron induced oxidative stress indicated by the reduction in lipid peroxidation, lactate dehydrogenase, aspartic acid transaminase, and alanine aminotransaminase activities and a rise in the glutathione-s-transferase, catalase, and superoxide dismutase and glutathione contents in the mice liver.

2023, The Journal of Physical Chemistry B

This study reports the carbon acidities of Cα and C4′ atoms in the Schiff bases of pyridoxal-5′-phosphate (PLP) and pyridoxamine-5′-phosphate (PMP) complexed with several biologically available metal ions (Mg 2+ , Ni 2+ , Zn 2+ , Cu 2+ , Al 3+ , and Fe 3+). Density functional theory calculations were carried out to determine the free energies of proton exchange reactions of a set of 18 carbon acids and a Schiff base used as a reference species. The experimental pK a values of such carbon acids were used to calibrate the computed free energies in a range of 30 pK a units. Eventually, the pK a s of the chelates were obtained by calculating the corresponding free energies against the same reference species and by considering the previous calibration. The carbon acidity of Cα in the chelates of Mg 2+ , Ni 2+ , Zn 2+ , and Cu 2+ varies between pK a ∼22 and pK a ∼13 whereas the pK a values of C4′ range between ∼18 and ∼7. Chelation of trivalent metals Al 3+ and Fe 3+ causes further decrease of the pK a values of Cα and C4′ down to ∼10 and ∼5, respectively. The results highlight the efficiency of the combined action of Schiff base formation and metal chelation to activate the Cα carbon of amino acids (pK a ∼29 for zwitterionic alanine). Our results explain that the experimental increase of transamination rates by Zn 2+ chelation is due to stabilization of the reactive Schiff base species with respect to the free ligand under physiological pH conditions. However, the increase in reactivity for transamination due to Cu 2+ and Al 3+ chelation is mostly due to C−H ligand activation. Each metal ion activates the Cα and C4′ carbon atoms to a different extent, which can be exploited to favor specific reactions on the amino acids in aqueous solution. Metal chelation hinders both intramolecular and intermolecular proton-transfer reactions of the imino, phenol, and carboxylate groups. This is the only apparent inconvenience of metal complexes in enzymatic reactions, which, in turn, proposes their consideration for enzyme inhibition.

2023, Journal of Physical Organic Chemistry

Properties of numerous selenium derivatives of maltol (3-hydroxy-2-methyl-4H-pyran-4-one), which is an important ligand in medicinal chemistry, were studied. Selenium derivatives were obtained using consecutive in silico replacements of maltol oxygen atoms, which produced three mono-substituted, three di-substituted and one tri-substituted derivatives. The geometry optimisations for these compounds in neutral, anionic and cationic forms were performed at the B1LYP/6-311++G** level of theory. The aromatic properties of the considered selenium compounds were studied in their heterocyclic rings using several indices of aromaticity: harmonic oscillator model of aromaticity, nucleus independent chemical shift(0), nucleus independent chemical shift(1), aromatic stabilisation energy, H index, para delocalisation index and multicentre index. The methods cover all of the main types of aromaticity indices: geometric, magnetic, energetic and electronic. The calculated data show the identical aromaticity order (cation > neutral molecule > anion) for maltol and its thio and seleno derivatives. The predicted aromaticity levels of selenomaltols were compared with the previously studied maltol and various thiomaltols.

2023, Journal of Physical Organic Chemistry

The aromaticity of heterocyclic pyran rings in selected hydroxypyrones and their anions and cations was studied using three aromaticity indices, HOMA, I6 and NICS. These values were determined for theoretical geometries obtained at the HF, SVWN, B3LYP and B1LYP levels of calculations with the 6–311 + +G(d,p) basis set. The data obtained show that the aromaticity for the hydroxypyrones under investigation increases in the order: anion < neutral molecule < cation. Copyright © 2004 John Wiley & Sons, Ltd.

2023, Beverages

White beers owe their name to their straw yellow colour deriving from the use of unmalted wheat, which also supplies a relatively high protein content causing haze formation. This study aimed to develop white-inspired craft beers made with combinations of three mixtures of barley malt/unmalted wheat (alternatively durum-var. Dauno III, soft-var. Risciola, or emmer-var. Padre Pio), two hop varieties (Cascade or Columbus), and two Saccharomyces cerevisiae strains (Belgian yeast and a high-ester producing yeast); and assess the single and interactive effects of these ingredients on physical, chemical, and sensory characteristics of the beers. According to the graphical representation of the results for the Principal Component Analysis, most of the samples appear overlapped since they had similar characteristics, but it was possible to highlight two clusters of beers different from the others: those produced with (a) Risciola wheat and Columbus hop and (b) Dauno III wheat, Cascade hop, ...

2023, Inorganic Chemistry

One-electron reduction of [Pt(bpy) 2 ] 2+ (bpy) 2,2′-bipyridyl) in aqueous solution results in the formation of black-green lustrous needles on solid electrodes. The crystalline needles grow perpendicularly from the substrate surface and reach lengths of 1-2 cm. Elemental analysis, X-ray photoelectron spectroscopy, and electrochemical measurements indicate that the new compound is a genuine Pt I complex with a d 9 electronic configuration and with the composition [Pt(bpy) 2 ]NO 3 ‚2H 2 O. X-ray crystallographic analysis shows that the crystalline needles consist of linear chains of discrete [Pt I (bpy) 2 ] units with a Pt-Pt distance of 3.563(1) Å and with each bipyridyl ligand overlapping face-to-face (eclipsed) with its nearest neighbor. At the monomeric level, the structure of [Pt I (bpy) 2 ] units exhibits a distorted square-planar configuration with structural parameters very similar to those of the parent Pt II complex, [Pt(bpy) 2 ](NO 3) 2 ‚H 2 O. The new linear-chain compound was prepared by chemical and electrochemical methods. The resulting crystals are relatively stable in air but oxidize slowly over a period of weeks. Scanning electron microscopy reveals that the crystals are tubular with a hollow near-hexagonal morphology. Cooperative effects influence the optical and electrical properties of the crystals. Because of extensive solid-state interactions between stacked monomeric [Pt I (bpy) 2 ] units, the crystals absorb strongly over the whole visible region and far into the near infrared. Their room temperature electrical conductivity is relatively high, 10 Ω-1 cm-1 .

2023, Journal of Chemistry

A new procedure for separation and preconcentration of trace amounts of Cu(II), Ni(II), Fe(III), Zn(II), Cr(III), Cd(II), and Pb(II) in fish samples was proposed. The procedure is based on the adsorption of these metal ions on the column of Amberlite XAD-7 as congo red complexes prior to their determination by flame atomic absorption spectrometry (FAAS). Several factors that can affect the sorption and elution efficiency of the metal ions were investigated and optimized. The sorption was quantitative in the pH range of 6.0-9.0 for Cu(II) and Ni(II), 5.5-8.0 for Fe(III), 6.0-8.5 for Zn(II) and Cd(II), and 7.0-8.5 for Cr(III) and Pb(II). The optimum pH for simultaneous retention was 7.5. The sorption capacity of the resin was found to be 0.89, 0.72, 0.82, 0.61, 0.53, 0.84, and 0.78 mg/g for Cu(II), Ni(II), Fe(III), Zn(II), Cr(III), Cd(II), and Pb(II), respectively. The precision of the method was evaluated as the relative standard deviation obtained by analyzing a series of six replicates and below 6% for all seven elements. The validation of the method was performed by the analysis of certified reference materials. The proposed method was successfully applied to separation/ preconcentration and determination of these metals in fish samples.

2023, European Journal of Inorganic Chemistry

A new siderophore analogue based on the mesocyclic diamine 1,5‐diazacyclooctane (DACO) functionalized with two additional hydroxamate donor pendant groups, 1,5‐diazacyclooctane‐1,5‐bis(N‐methylacetohydroxamic acid) (DACODMAHA), has been synthesized from the corresponding diacetate derivative (DACODA). The complexation behaviour of this ligand towards CuII and FeIII in aqueous solution has been studied by potentiometry, UV/Vis and EPR spectroscopy and magnetic moment measurements. The CuII complexation involves the formation of a mononuclear species with a tetradentate mixed amine/hydroxamate coordination mode, whereas the FeIII complexation involves a binuclear species with Fe2L3 stoichiometry and normal {O,O}‐hydroxamate coordination mode. The redox potential of the iron complexes and the corresponding electron transfer mechanism are also evaluated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

2023, Journal of Chemistry

Silica-C18 bonded disk modified by a four-dentate Schiff base has been used for preconcentration of cadmium in table salt samples followed by flame atomic absorption spectrometry. The method is based on the adsorption of Cd on 1,2-bis(pyridin-2-ylmethylene) hydrazine as Schiff base ligand on silica-C18 disk. The effects of several factors such as type and concentration of the eluent, pH of sample solution, amount of ligand, and breakthrough volume have been optimized based on one variable at a time. In optimum conditions (type of eluent, HNO31.0 mol/L; volume of eluent, 5.0 mL; solution pH, 9.0; breakthrough volume, 1000.0 mL), preconcentration factor of the present method is about 200. The resultant limit of detection is 5.0 μg/L. Finally, the performance of the method has been evaluated for extraction and determination of Cd (II) in salt samples at milligram per liter concentration, and satisfactory results have been obtained (RSD ≤ 2.0%).

2023

Title page, summary and table of contents only. The complete thesis in print form is available from the University of Adelaide Library.