A critical review of a typical research system for food-derived metal-chelating peptides: Production, characterization, identification, digestion, and absorption.

In the past decade, food-derived metal-chelating peptides (MCPs) have attracted significant attention from researchers working towards the prevention of metal (viz., iron, zinc, and calcium) deficiency phenomenon by primarily inhibiting the precipitation of metals caused by the gastrointestinal environment and exogenous substances (including phytic and oxalic acids). However, for the improvement of limits of current knowledge foundations and future investigation directions of MCP or their derivatives, several review categories should be improved and emphasized. The species' uniqueness and differences in MCP productions highly contribute to the different values of chelating ability with particular metal ions, whereas comprehensive reviews of chelation characterization determined by various kinds of technique support different horizons for explaining the chelation and offer options for the selection of characterization methods. The reviews of chelation mechanism clearly demonstrate the involvement of potential groups and atoms in chelating metal ions. The discussions of digestive stability and absorption in various kinds of absorption model in vitro and in vivo as well as the theory of involved cellular absorption channels and pathways are systematically reviewed and highlighted compared with previous reports as well. Meanwhile, the chelation mechanism on the molecular docking level, the binding mechanism in amino acid identification level, the utilizations of everted rat gut sac model for absorption, and the involvement of cellular absorption channels and pathway are strongly recommended as novelty in this review. This review makes a novel contribution to the literature by the comprehensive prospects for the research and development of food-derived mineral supplements.

Exogenous chelating agents influence growth, physiological characteristics and cell ultrastructure of Robinia pseudoacacia seedlings under lead-cadmium stress.

Heavy metal pollution of soil, especially by lead (Pb) and cadmium (Cd), is a serious problem worldwide. The application of safe chelating agents, combined with the growing of tolerant trees, constitutes an approach for phytoremediation of heavy-metal-contaminated soil. This study aimed to determine whether the two safe chelators, tetrasodium glutamate diacetate (GLDA) and citric acid (CA), could improve the phytoremediation capacity of black locust (Robinia pseudoacacia L.) in a Pb-Cd-contaminated soil and to find the key factors affecting the biomass accumulation of stressed black locust. In Pb- and Cd-stressed black locust plants, medium- and high-concentration GLDA treatment inhibited the growth, chlorophyll synthesis and maximum photochemical efficiency (Fv/Fm), promoted the absorption of Pb and Cd ions and resulted in the shrinkage of chloroplasts and starch grains when compared with those in Pb- and Cd-stressed plants that were not treated with GLDA. The effects of CA on plant growth, ion absorption, chlorophyll content, chlorophyll fluorescence and organelle size were significantly weaker than those of GLDA. The effect of both agents on Cd absorption was greater than that on Pb absorption in all treatments. The levels of chlorophyll a and plant tissue Cd and rates of starch metabolism were identified as the key factors affecting plant biomass accumulation in GLDA and CA treatments. In the future, GLDA can be combined with functional bacteria and/or growth promoters to promote the growth of Pb- and Cd-stressed plants and to further improve the soil restoration efficiency following pollution by heavy metals. Application of CA combined with the growing of black locust plants has great potential for restoring the Cd-polluted soil. These findings also provide insights into the practical use of GLDA and CA in phytoremediation by R. pseudoacacia and the tolerant mechanisms of R. pseudoacacia to Pb-Cd-contaminated soil.

Evaluation of Copper Chelation Therapy in a Transgenic Rat Model of Cerebral Amyloid Angiopathy.

Cerebral amyloid angiopathy (CAA) is characterized by the accumulation of the amyloid ß (Aß) protein in blood vessels and leads to hemorrhages, strokes, and dementia in elderly individuals. Recent reports have shown elevated copper levels colocalized with vascular amyloid in human CAA and Alzheimer's disease patients, which have been suggested to contribute to cytotoxicity through the formation of reactive oxygen species. Here, we treated a transgenic rat model of CAA (rTg-DI) with the copper-specific chelator, tetrathiomolybdate (TTM), via intraperitoneal (IP) administration for 6 months to determine if it could lower copper content in vascular amyloid deposits and modify CAA pathology. Results showed that TTM treatment led to elevated Aß load in the hippocampus of the rTg-DI rats and increased microbleeds in the wild type (WT) animals. X-ray fluorescence microscopy was performed to image the distribution of copper and revealed a surprising increase in copper colocalized with Aß aggregates in TTM-treated rTg-DI rats. Unexpectedly, we also found an increase in the copper content in unaffected vessels of both rTg-DI and WT animals. These results show that IP administration of TTM was ineffective in removing copper from vascular Aß aggregates in vivo and increased the development of disease pathology in CAA.

In Vivo Uranium Decorporation by a Tailor-Made Hexadentate Ligand.

The sequestration of uranium, particularly from the deposited bones, has been an incomplete task in chelation therapy for actinide decorporation. Part of the reason is that all previous decorporation ligands are not delicately designed to meet the coordination requirement of uranyl cations. Herein, guided by DFT calculation, we elaborately design a hexadentate ligand (TAM-2LI-MAM2), whose preorganized planar oxo-donor configuration perfectly matches the typical coordination geometry of the uranyl cation. This leads to an ultrahigh binding affinity to uranyl supported by an in vitro desorption experiment of uranyl phosphate. Administration of this ligand by prompt intraperitoneal injection demonstrates its uranyl removal efficiencies from the kidneys and bones are up to 95.4% and 81.2%, respectively, which notably exceeds all the tested chelating agents as well as the clinical drug ZnNa3-DTPA, setting a new record in uranyl decorporation efficacy.

Copper toxicity towards Campylobacter jejuni is enhanced by the nickel chelator dimethylglyoxime.

The nickel (Ni)-chelator dimethylglyoxime (DMG) was found to be bacteriostatic towards Campylobacter jejuni. Supplementation of nickel to DMG-containing media restored bacterial growth, whereas supplementation of cobalt or zinc had no effect on the growth inhibition. Unexpectedly, the combination of millimolar levels of DMG with micromolar levels of copper (Cu) was bactericidal, an effect not seen in select Gram-negative pathogenic bacteria. Both the cytoplasmic Ni-binding chaperone SlyD and the twin arginine translocation (Tat)-dependent periplasmic copper oxidase CueO were found to play a central role in the Cu-DMG hypersensitivity phenotype. Ni-replete SlyD is needed for Tat-dependent CueO translocation to the periplasm, whereas Ni-depleted (DMG-treated) SlyD is unable to interact with the CueO Tat signal peptide, leading to mislocalization of CueO and increased copper sensitivity. In support of this model, C. jejuni ΔslyD and ΔcueO mutants were more sensitive to copper than the wild-type (WT); CueO was less abundant in the periplasmic fraction of ΔslyD or DMG-grown WT cells, compared to WT cells grown on plain medium; SlyD binds the CueO signal sequence peptide, with DMG inhibiting and nickel enhancing the binding, respectively. Injection of Cu-DMG into Galleria mellonella before C. jejuni inoculation significantly increased the insect survival rate compared to the control group. In chickens, oral administration of DMG or Cu-DMG decreased and even abolished C. jejuni colonization in some cases, compared to both water-only and Cu-only control groups. The latter finding is important, since campylobacteriosis is the leading bacterial foodborne infection, and chicken meat constitutes the major foodborne source.

Zinc as a Drug for Wilson's Disease, Non-Alcoholic Liver Disease and COVID-19-Related Liver Injury.

Zinc is the second most abundant trace element in the human body, and it plays a fundamental role in human physiology, being an integral component of hundreds of enzymes and transcription factors. The discovery that zinc atoms may compete with copper for their absorption in the gastrointestinal tract let to introduce zinc in the therapy of Wilson's disease, a congenital disorder of copper metabolism characterized by a systemic copper storage. Nowadays, zinc salts are considered one of the best therapeutic approach in patients affected by Wilson's disease. On the basis of the similarities, at histological level, between Wilson's disease and non-alcoholic liver disease, zinc has been successfully introduced in the therapy of non-alcoholic liver disease, with positive effects both on insulin resistance and oxidative stress. Recently, zinc deficiency has been indicated as a possible factor responsible for the susceptibility of elderly patients to undergo infection by SARS-CoV-2, the coronavirus responsible for the COVID-19 pandemic. Here, we present the data correlating zinc deficiency with the insurgence and progression of Covid-19 with low zinc levels associated with severe disease states. Finally, the relevance of zinc supplementation in aged people at risk for SARS-CoV-2 is underlined, with the aim that the zinc-based drug, classically used in the treatment of copper overload, might be recorded as one of the tools reducing the mortality of COVID-19, particularly in elderly people.

Formulation design, optimization and in vivo evaluation of oral co-encapsulated resveratrol-humic acid colloidal polymeric nanocarriers.

The study aims at formulation and optimization of resveratrol and humic acid co-encapsulated colloidal polymeric nanocarriers to improve stability, oral bioavailability, and antiradical activity of water-insoluble, resveratrol. The eudragit E100 polymeric material was used to fabricate resveratrol and humic acid co-encapsulated oral colloidal polymeric nanocarriers (Res-HA-co-CPNs) using emulsification-diffusion-evaporation method. Taguchi orthogonal array design was employed to check the effect of formulation factors on in vitro physicochemical characteristics. The optimized formulation was further evaluated for oral bioavailability as well as for antiradical potential. Optimized Res-HA-co-CPNs demonstrated spherical and smooth surface including mean particle size, 120.56 ± 18.8 nm; polydispersity index, 0.122; zeta potential, +38.25 mV; and entrapment efficiency, 82.37 ± 1.49%. Solid-state characterization confirmed the amorphous characteristic of optimized Res-HA-co-CPNs. In vitro release profile of Res-HA-co-CPNs showed sustained release behavior up to 48 h and CPNs were found to remain stable at the refrigerated condition for 6 months. In vivo pharmacokinetic studies revealed significant (p < 0.05) improvement of ∼62.76-fold in oral bioavailability. The radical-scavenging activity was found to be increased with time and after 72 h, it was analogous to pure Res. IC50 values were reported to be decreased with time. Henceforth, developed Res-HA-co-CPNs was proven to be a proficient dosage form to increase stability, oral bioavailability, and antiradical activity of resveratrol.HighlightsResveratrol-humic acid co-encapsulated colloidal polymeric nanocarriers (Res-HA-co-CPNs) were fabricated by emulsification-diffusion-evaporation method and optimized by Taguchi orthogonal array design.The Res-HA-co-CPNs revealed favorable mean particle size and percent encapsulation efficiency with a spherical and smooth surface.The Res-HA-co-CPNs showed diffusion-controlled release of Res and were found to be stable at the refrigerated condition for 6 months.The optimized Res-HA-co-CPNs demonstrated significantly (p < 0.05) higher oral bioavailability with respect to pure Res and PM.The optimized Res-HA-co-CPNs demonstrated higher radical-scavenging activity with respect to time.

Lipoic acid. Kinetics and pluripotent biological properties and derivatives.

Lipoic acid (LA) is globally known and its supplements are widely used. Despite its importance for the organism it is not considered a vitamin any more. The multiple metabolic forms and the differences in kinetics (absorption, distribution and excretion), as well as the actions of its enantiomers are analysed in the present article together with its biosynthetic path. The proteins involved in the transfer, biotransformation and activity of LA are mentioned. Furthermore, the safety and the toxicological profile of the compound are commented, together with its stability issues. Mechanisms of lipoic acid intervention in the human body are analysed considering the antioxidant and non-antioxidant characteristics of the compound. The chelating properties, the regenerative ability of other antioxidants, the co-enzyme activity and the signal transduction by the implication in various pathways will be discussed in order to be elucidated the pleiotropic effects of LA. Finally, lipoic acid integrating analogues are mentioned under the scope of the multiple pharmacological actions they acquire towards degenerative conditions.

Acylated Anthocyanins from Red Cabbage and Purple Sweet Potato Can Bind Metal Ions and Produce Stable Blue Colors.

Red cabbage (RC) and purple sweet potato (PSP) are naturally rich in acylated cyanidin glycosides that can bind metal ions and develop intramolecular π-stacking interactions between the cyanidin chromophore and the phenolic acyl residues. In this work, a large set of RC and PSP anthocyanins was investigated for its coloring properties in the presence of iron and aluminum ions. Although relatively modest, the structural differences between RC and PSP anthocyanins, i.e., the acylation site at the external glucose of the sophorosyl moiety (C2-OH for RC vs. C6-OH for PSP) and the presence of coordinating acyl groups (caffeoyl) in PSP anthocyanins only, made a large difference in the color expressed by their metal complexes. For instance, the Al3+-induced bathochromic shifts for RC anthocyanins reached ca. 50 nm at pH 6 and pH 7, vs. at best ca. 20 nm for PSP anthocyanins. With Fe2+ (quickly oxidized to Fe3+ in the complexes), the bathochromic shifts for RC anthocyanins were higher, i.e., up to ca. 90 nm at pH 7 and 110 nm at pH 5.7. A kinetic analysis at different metal/ligand molar ratios combined with an investigation by high-resolution mass spectrometry suggested the formation of metal-anthocyanin complexes of 1:1, 1:2, and 1:3 stoichiometries. Contrary to predictions based on steric hindrance, acylation by noncoordinating acyl residues favored metal binding and resulted in complexes having much higher molar absorption coefficients. Moreover, the competition between metal binding and water addition to the free ligands (leading to colorless forms) was less severe, although very dependent on the acylation site(s). Overall, anthocyanins from purple sweet potato, and even more from red cabbage, have a strong potential for development as food colorants expressing red to blue hues depending on pH and metal ion.

Polyphenols as Potential Metal Chelation Compounds Against Alzheimer's Disease.

Alzheimer's disease (AD) is the most common neurodegenerative disease affecting more than 50 million people worldwide. The pathology of this multifactorial disease is primarily characterized by the formation of amyloid-ß (Aß) aggregates; however, other etiological factors including metal dyshomeostasis, specifically copper (Cu), zinc (Zn), and iron (Fe), play critical role in disease progression. Because these transition metal ions are important for cellular function, their imbalance can cause oxidative stress that leads to cellular death and eventual cognitive decay. Importantly, these transition metal ions can interact with the amyloid-ß protein precursor (AßPP) and Aß42 peptide, affecting Aß aggregation and increasing its neurotoxicity. Considering how metal dyshomeostasis may substantially contribute to AD, this review discusses polyphenols and the underlying chemical principles that may enable them to act as natural chelators. Furthermore, polyphenols have various therapeutic effects, including antioxidant activity, metal chelation, mitochondrial function, and anti-amyloidogenic activity. These combined therapeutic effects of polyphenols make them strong candidates for a moderate chelation-based therapy for AD.

Food-derived antioxidants and COVID-19.

SARS-CoV-2 (previously 2019-nCoV), the pathogenic agent of COVID-19 disease, started to expand from Wuhan, China, on December 2019 and in 2 months, it spread worldwide giving origin to a pandemic. COVID-19 has a stronger transmission capacity by inhalation of infectious aerosols and after an incubation time of 3-14 days, it may be responsible for diseases ranging from the asymptomatic to fatal consequences. COVID-19 has emerged as a multifaceted, multisystem, multi-organ disorder, which produces its pathogenic effects through a quite ubiquitous target at the level of multiple organs and in which oxidative stress and inflammatory process play relevant roles. Thus, besides the development of a pharmacological therapy, in the field of alternative and coadjutant therapeutic, the use of dietary supplements or nutraceuticals for the prevention or treatment of SARS-CoV-2 infection may be a useful strategy. Herein, we specifically comment on some literature evidences, which link the food-derived antioxidants and metal-chelating agents with treatment and prevention of oxidative stress and inflammation that play a key role in the progression of COVID-19. PRACTICAL APPLICATIONS: Oxidative stress and inflammation are key factors increasing COVID-19 severity especially in the presence of chronic diseases associated with the antioxidant system fragility. These evidences support the recommendation of antioxidants supplementation as useful strategies against COVID-19. In light with these observations, herein, a comment which describes the major antioxidants and metal-chelating agents from food sources that might be useful for the treatment and prevention of oxidative stress and inflammation during COVID-19.

The effects of clioquinol in morphogenesis, cell membrane and ion homeostasis in Candida albicans.

BACKGROUND: Candida albicans is the most prevalent opportunistic fungal pathogen. Development of antifungals with novel targets is necessary for limitations of current antifungal agents and the emergence of drug resistance. The antifungal activity of clioquinol was widely accepted while the precise mechanism was poorly understood. Hence, we aimed to seek for the possible mechanism of clioquinol against Candida albicans in the present study. RESULTS: Clioquinol could inhibit hyphae formation in a concentration-dependent manner in multiple liquid and solid media. The concentration and time-dependent anti-biofilm activities were observed in different incubation periods quantitatively and qualitatively. Further investigation found that clioquinol disrupted cell membrane directly in high concentration and induced depolarization of the membrane in low concentration. As for the influence on ion homeostasis, the antifungal effects of clioquinol could be reversed by exogenous addition of metal ions. Meanwhile, the minimum inhibitory concentration of clioquinol was increased in media supplemented with exogenous metal ions and decreased in media supplemented with exogenous metal chelators. We also found that the cellular labile ferrous iron level decreased when fungal cells were treated with clioquinol. CONCLUSION: These results indicated that clioquinol could inhibit yeast-hyphae transition and biofilm formation in Candida albicans. The effect on the cell membrane was different depending on different concentrations of clioquinol. Meanwhile, clioquinol could interfere with ion homeostasis as metal chelators for zinc, copper and iron, which was quite different with current common antifungal agents. All in all, clioquinol can be a new promising antifungal agent with novel target though more studies are needed to better understand the precise antifungal mechanism.

Evaluating the efficacy of a ferrous-ion-chelating peptide from Alaska pollock frame for the improvement of iron nutritional status in rats.

This study aimed to investigate the effects of ferrous-ion-chelating peptides from Alaska pollock frames (APFP-Fe) on iron deficiency in anaemic rats. We hydrolysed the Alaska pollock frames to obtain a peptide with an average molecular weight of 822 Da. The bioavailability of APFP-Fe was tested using animal experiments. Wistar rats were randomly divided into six groups: an iron deficiency control group, a normal control group, and iron deficiency groups treated with ferrous sulfate (FeSO4) or low-, medium-, or high-dose APFP-Fe. Rats in the iron deficiency groups were fed an iron-deficient diet to establish the iron deficiency anaemia (IDA) model. After the model was established, different iron supplements were given to rats once per day via intragastric administration for 21 days. The results showed that APFP-Fe had restorative effects, returning the body weight, weight gain, height, and haematological parameters in IDA rats to normal levels. In addition, compared with FeSO4, APFP-Fe promoted significant weight gain and effectively improved haemoglobin, serum iron and transferrin levels, and recovery of the capacity of iron binding with transferrin, especially at the medium and high doses. These findings suggest that APFP-Fe is an effective source of iron for improving the iron nutritional status in IDA rats and shows promise as a new source of iron supplementation.

Organic selenium derived from chelation of soybean peptide-selenium and its functional properties in vitro and in vivo.

Organic selenium has been widely explored as an important source of selenium (Se) supplement due to its low toxicity and easy absorption. In the present study, a new type of organic selenium was fabricated by chelating Se with soybean protein isolate peptides (SPIPs), and its physio-chemical properties, structural characteristics, and antioxidant activities were investigated. Results indicated that the structure of the SPIP molecule was folded and aggregated during the chelation process. SPIP-Se exhibited stronger hydroxyl radical scavenging activity and reducing power than SPIP in vitro. In addition, SPIP-Se could repair the H2O2-induced oxidative damage of Caco-2 cells by enhancing the activities of antioxidant enzymes. The in vivo assay showed that SPIP-Se showed much less toxicity than inorganic Se supplements, and exhibited a more positive effect on the activities of key enzymes including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and aspartate aminotransferase (AST). These findings suggest that SPIP-Se could be developed as an effective dietary Se supplement in the food or pharmaceutical field in the future.

Isolation and identification of iron-chelating peptides from casein hydrolysates.

Iron deficiency is a common nutritional disorder worldwide. Peptides derived from protein hydrolysates have recently attracted interest as novel iron chelators due to their superiority in terms of increasing solubility, bioavailability, absorption and stability. The aim of this study was to isolate and identify iron-chelating peptides from casein hydrolysates. Casein was hydrolyzed (trypsin, 3 h) and subsequently isolated using ultrafiltration and RP-HPLC. Four iron-chelating casein hydrolysate peptides, named CHP-1, CHP-2, CHP-3 and CHP-4, were identified by LC-MS/MS, and their amino acid sequences were Glu-Asp-Val-Pro-Ser-Glu-Arg (EDVPSER), His-Lys-Glu-Met-Pro-Phe-Pro-Lys (HKEMPFPK), Asn-Met-Ala-Ile-Asn-Pro-Ser-Lys (NMAINPSK) and Ala-Val-Pro-Tyr-Pro-Gln-Arg (AVPYPQR), with molecular weights of 830.6120 Da, 1012.5280 Da, 873.4440 Da and 829.4570 Da, respectively. The artificially synthesized peptides of CHP-1, CHP-2, CHP-3 and CHP-4 were verified, and their iron-chelating rates were 11.14%, 8.02%, 7.57% and 59.76%, respectively. These results suggested that the isolated iron-chelating peptides might serve as potential iron supplements and be used as food additives and functional foods.

Is hydroxypyridonate 3,4,3-LI(1,2-HOPO) a good competitor of fetuin for uranyl metabolism?

Uranium is widespread in the environment, resulting both from natural occurrences and anthropogenic activities. Its toxicity is mainly chemical rather than radiological. In the blood it is transported as uranyl UO22+ cation and forms complexes with small ligands like carbonates and with some proteins. From there it reaches the skeleton, its main target organ for accumulation. Fetuin is a serum protein involved in biomineralization processes, and it was demonstrated to be the main UO22+-binder in vitro. Fetuin's life cycle ends in bone. It is thus suspected to be a key protagonist of U accumulation in this organ. Up to now, there has been no effective treatment for the removal of U from the body and studies devoted to the interactions involving chelating agents with both UO22+ and its protein targets are lacking. The present work aims at studying the potential role of 3,4,3-LI(1,2-HOPO) as a promising chelating agent in competition with fetuin. The apparent affinity constant of 3,4,3-LI(1,2-HOPO) was first determined, giving evidence for its very high affinity similar to that of fetuin. Chromatography experiments, aimed at identifying the complexes formed and quantifying their UO22+ content, and spectroscopic structural investigations (XAS) were carried out, demonstrating that 3,4,3-LI(1,2-HOPO) inhibits/limits the formation of fetuin-uranyl complexes under stoichiometric conditions. But surprisingly, possible ternary complexes stable enough to remain present after the chromatographic process were identified under sub-stoichiometric conditions of HOPO versus fetuin. These results contribute to the understanding of the mechanisms accounting for U residual accumulation despite chelation therapy after internal contamination.

Copper(I)-binding properties of de-coppering drugs for the treatment of Wilson disease. α-Lipoic acid as a potential anti-copper agent.

Wilson disease is an autosomal recessive genetic disorder caused by loss-of-function mutations in the P-type copper ATPase, ATP7B, which leads to toxic accumulation of copper mainly in the liver and brain. Wilson disease is treatable, primarily by copper-chelation therapy, which promotes copper excretion. Although several de-coppering drugs are currently available, their Cu(I)-binding affinities have not been quantitatively characterized. Here we determined the Cu(I)-binding affinities of five major de-coppering drugs - D-penicillamine, trientine, 2,3-dimercapto-1-propanol, meso-2,3-dimercaptosuccinate and tetrathiomolybdate - by exploring their ability to extract Cu(I) ions from two Cu(I)-binding proteins, the copper chaperone for cytochrome c oxidase, Cox17, and metallothionein. We report that the Cu(I)-binding affinity of these drugs varies by four orders of magnitude and correlates positively with the number of sulfur atoms in the drug molecule and negatively with the number of atoms separating two SH groups. Based on the analysis of structure-activity relationship and determined Cu(I)-binding affinity, we hypothesize that the endogenous biologically active substance, α-lipoic acid, may be suitable for the treatment of Wilson disease. Our hypothesis is supported by cell culture experiments where α-lipoic acid protected hepatic cells from copper toxicity. These results provide a basis for elaboration of new generation drugs that may provide better therapeutic outcomes.

Evaluation of aluminium mobilization from its soil mineral pools by simultaneous effect of Aspergillus strains' acidic and chelating exometabolites.

This contribution investigates aluminium mobilization from main aluminium pools in soils, phyllosilicates and oxyhydroxides, by acidic and chelating exometabolites of common soil fungi Aspergillus niger and A. clavatus. Their exometabolites' acidity as well as their ability to extract aluminium from solid mineral phases differed significantly during incubation. While both strains are able to mobilize aluminium from boehmite and aluminium oxide mixture to some extent, A. clavatus struggles to mobilize any aluminium from gibbsite. Furthermore, passive and active fungal uptake of aluminium enhances its mobilization from boehmite, especially in later growth phase, with strong linear correlation between aluminium bioaccumulated fraction and increasing culture medium pH. We also provide data on concentrations of oxalate, citrate and gluconate which are synthesized by A. niger and contribute to aluminium mobilization. Compared to boehmite-free treatment, fungus reduces oxalate production significantly in boehmite presence to restrict aluminium extraction efficiency. However, in presence of high phyllosilicates' dosages, aluminium is released to an extent that acetate and citrate is overproduced by fungus. Our results also highlight fungal capability to significantly enhance iron and silicon mobility as these elements are extracted from mineral lattice of phyllosilicates by fungal exometabolites alongside aluminium.

Polyethyleneimine methylphosphonate: towards the design of a new class of macromolecular actinide chelating agents in the case of human exposition.

The use of uranium and to a minor extent plutonium as fuel for nuclear energy production or as components in military applications is under increasing public pressure. Uranium is weakly radioactive in its natural isotopy but its chemical toxicity, combined with its large scale industrial utilization, makes it a source of concern in terms of health impact for workers and possibly the general population. Plutonium is an artificial element that exhibits both chemical and radiological toxicities. So far, uranium (under its form uranyl, U(vi)) or plutonium (as Pu(iv)) decorporation or protecting strategies based on molecular design have been of limited efficiency to remove the actinide once incorporated after human exposure. In all cases, after human exposure, plutonium and uranium are retained in main target organs (liver, kidneys) as well as skeleton although they exhibit differences in their biodistribution. Polymers could represent an alternative strategy as their tropism for specific target organs has been reported. We recently reported on the complexation properties of methylcarboxylated polyethyleneimine (PEI-MC) with uranyl. In this report we extend our work to methylphosphonated polyethyleneimine (PEI-MP) and to the comparison between actinide oxidation states +IV (thorium) and +VI (uranyl). As a first step, thorium (Th(iv)) was used as a chemical surrogate of plutonium because of the difficulty in handling the latter in the laboratory. For both cations, U(vi) and Th(iv), the uptake curve of PEI-MP was recorded. The functionalized PEI-MP exhibits a maximum loading capacity comprised of between 0.56 and 0.80 mg of uranium (elemental) and 0.15-0.20 mg of thorium (elemental) per milligram of PEI-MP. Complexation sites of U(vi) and Th(iv) under model conditions close to physiological pH were then characterized with a combination of Fourier transform Infra Red (FT-IR) and Extended X-Ray Absorption Fine Structure (EXAFS). Although both cations exhibit different coordination modes, similar structural parameters with phosphonate functions were obtained. For example, the coordination sites are composed of fully monodentate phosphonate functions of the polymer chains. These physical chemical data represent a necessary basic chemistry approach before envisioning further biological evaluations of PEI-MP polymers towards U(vi) and Pu/Th(iv) contamination.

Antioxidant and mercury chelating activity of Psidium guajava var. pomifera L. leaves hydroalcoholic extract.

Mercury (Hg) is widely distributed in the environment and is known to produce several adverse effects in organisms. The aim of the present study was to examine the in vitro antioxidant activity and Hg chelating ability of the hydroalcoholic extract of Psidium guajava leaves (HEPG). In addition, the potential protective effects of HEPG against Hg(II) were evaluated using a yeast model (Saccharomyces cerevisiae). HEPG was found to exert significant antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl scavenger and inhibition of lipid peroxidation induced by Fe(II) assays in a concentration-dependent manner. The extract also exhibited significant Hg(II) chelating activity. In yeast, Hg(II) induced a significant decrease in cell viability. In contrast, HEPG partially prevented the fall in cell viability induced by Hg(II). In conclusion, HEPG exhibited protective effects against Hg(II)-mediated toxicity, which may be related to both antioxidant and Hg(II)-chelating activities.