Synthetic Chelators Research Articles

Cultivating resilience: Harnessing pyoverdine-producing Pseudomonas to contrast iron deficiency in cucumber plants

Iron (Fe) deficiency in crops significantly reduces yield, impacting agricultural productivity worldwide. Synthetic Fe chelates are commonly applied as fertilizers to address this issue, but their synthetic nature and prolonged use poses environmental risks. Thus, inoculation of plant growth-promoting bacteria rises as an alternative to enhance Fe uptake in crops while minimizing reliance on synthetic chelates. This study aimed to examine the influence of Pseudomonas RMC4 inoculation and pyoverdine application on cucumber plants cultivated hydroponically under Fe deficiency conditions. Evaluations included the SPAD index, plant biomass, root morphology, Fe-chelate reductase activity, gene expression, and ionomic analysis. Following Fe deficiency, Pseudomonas RMC4 inoculation improved the SPAD index, increased dry weight, enhanced root development, and facilitated Fe acquisition mechanisms, thus, fostering the endogenous resilience of the plant to the limited Fe availability. This improvement was observed with bacterial inoculation or pyoverdine application alongside an insoluble Fe source (ferrihydrite). Overall, the results suggest the beneficial impact of Pseudomonas RMC4 inoculation in alleviating symptoms of Fe deficiency. Future studies will investigate bacterial application under field conditions to assess its potential in replacing synthetic Fe-chelates fertilizers in crop production in favor of more sustainable agriculture.

Iron Chelation in Soil: Scalable Biotechnology for Accelerating Carbon Dioxide Removal by Enhanced Rock Weathering.

Enhanced rock weathering (EW) is an emerging atmospheric carbon dioxide removal (CDR) strategy being scaled up by the commercial sector. Here, we combine multiomics analyses of belowground microbiomes, laboratory-based dissolution studies, and incubation investigations of soils from field EW trials to build the case for manipulating iron chelators in soil to increase EW efficiency and lower costs. Microbial siderophores are high-affinity, highly selective iron (Fe) chelators that enhance the uptake of Fe from soil minerals into cells. Applying RNA-seq metatranscriptomics and shotgun metagenomics to soils and basalt grains from EW field trials revealed that microbial communities on basalt grains significantly upregulate siderophore biosynthesis gene expression relative to microbiomes of the surrounding soil. Separate in vitro laboratory incubation studies showed that micromolar solutions of siderophores and high-affinity synthetic chelator (ethylenediamine-N,N'-bis-2-hydroxyphenylacetic acid, EDDHA) accelerate EW to increase CDR rates. Building on these findings, we develop a potential biotechnology pathway for accelerating EW using the synthetic Fe-chelator EDDHA that is commonly used in agronomy to alleviate the Fe deficiency in high pH soils. Incubation of EW field trial soils with potassium-EDDHA solutions increased potential CDR rates by up to 2.5-fold by promoting the abiotic dissolution of basalt and upregulating microbial siderophore production to further accelerate weathering reactions. Moreover, EDDHA may alleviate potential Fe limitation of crops due to rising soil pH with EW over time. Initial cost-benefit analysis suggests potassium-EDDHA could lower EW-CDR costs by up to U.S. $77 t CO2 ha-1 to improve EW's competitiveness relative to other CDR strategies.

Targeting Biometals in Alzheimer's Disease with Metal Chelating Agents Including Coumarin Derivatives.

Numerous physiological processes happening in the human body, including cerebral development and function, require the participation of biometal ions such as iron, copper, and zinc. Their dyshomeostasis may, however, contribute to the onset of Alzheimer's disease (AD) and potentially other neurodegenerative diseases. Chelation of biometal ions is therefore atherapeutic strategy against AD. This review provides asurvey of natural and synthetic chelating agents that are or could potentially be used to target the metal hypothesis of AD. Since metal dyshomeostasis is not the only pathological aspect of AD, and the nature of this disorder is very complex and multifactiorial, the most efficient therapeutics should target as many neurotoxic factors as possible. Various coumarin derivatives match this description and apart from being able to chelate metal ions, they exhibit the capacity to inhibit cholinesterases (ChEs) and monoamine oxidase B (MAO-B) while also possessing antioxidant, anti-inflammatory, and numerous other beneficial effects. Compounds based on the coumarin scaffold therefore represent a desirable class of anti-AD therapeutics.

Harnessing bio-based chelating agents for sustainable synthesis of AgNPs: Evaluating their inherent attributes and antimicrobial potency in conjunction with honey

Greenly synthesized nanoparticles have garnered attention due to their low environmental footprint, but impurities limit their applications. A novel semi-organic method for synthesizing silver nanoparticles (AgNPs) using bio-based chelating fuels (Beta vulgaris subsp., Spinacia oleracea, and Ipomoea batatas) reduces the undesirable impurities. The study also showcases the impact of bio-based chelating fuel on various characteristics of AgNPs in comparison to synthetic chelating fuel. The antimicrobial efficacy of the synthesized AgNPs in conjunction with honey was also assessed against E. coli. The XRD analysis showed cubic structure of AgNPs. The FESEM and TEM analysis showed that the well-connected spherical-shaped AgNPs (∼3–120 nm diameter) while EDS confirmed the presence of Ag in all samples. The TEM analysis also revealed layers of carbonates in AgNPs synthesized using bio-based chelating fuels. XPS investigation confirmed the absence of any prominent impurities in prepared samples and AgNPs have not experienced oxidation on their surface. However, notable surface charging effects due to the uneven conductivity of the particles were observed. The broth dilution method showed that all mixtures containing AgNPs in combination with honey exhibited a significant bacterial growth reduction over a period of 120 h. The highest growth reduction of ∼75 % is obtained for the mixture having AgNPs (Ipomoea batatas) while the least growth reduction of ∼51 % is obtained for the mixture having AgNPs (Beta vulgaris subsp.). The findings affirm that AgNPs can be successfully synthesized using bio-based chelating fuels with negligible ecological consequences and devoid of contaminants. Moreover, the synthesized AgNPs can be employed in conjunction with honey for antibacterial purposes.

The Importance and Essentiality of Natural and Synthetic Chelators in Medicine: Increased Prospects for the Effective Treatment of Iron Overload and Iron Deficiency.

The supply and control of iron is essential for all cells and vital for many physiological processes. All functions and activities of iron are expressed in conjunction with iron-binding molecules. For example, natural chelators such as transferrin and chelator-iron complexes such as haem play major roles in iron metabolism and human physiology. Similarly, the mainstay treatments of the most common diseases of iron metabolism, namely iron deficiency anaemia and iron overload, involve many iron-chelator complexes and the iron-chelating drugs deferiprone (L1), deferoxamine (DF) and deferasirox. Endogenous chelators such as citric acid and glutathione and exogenous chelators such as ascorbic acid also play important roles in iron metabolism and iron homeostasis. Recent advances in the treatment of iron deficiency anaemia with effective iron complexes such as the ferric iron tri-maltol complex (feraccru or accrufer) and the effective treatment of transfusional iron overload using L1 and L1/DF combinations have decreased associated mortality and morbidity and also improved the quality of life of millions of patients. Many other chelating drugs such as ciclopirox, dexrazoxane and EDTA are used daily by millions of patients in other diseases. Similarly, many other drugs or their metabolites with iron-chelation capacity such as hydroxyurea, tetracyclines, anthracyclines and aspirin, as well as dietary molecules such as gallic acid, caffeic acid, quercetin, ellagic acid, maltol and many other phytochelators, are known to interact with iron and affect iron metabolism and related diseases. Different interactions are also observed in the presence of essential, xenobiotic, diagnostic and theranostic metal ions competing with iron. Clinical trials using L1 in Parkinson's, Alzheimer's and other neurodegenerative diseases, as well as HIV and other infections, cancer, diabetic nephropathy and anaemia of inflammation, highlight the importance of chelation therapy in many other clinical conditions. The proposed use of iron chelators for modulating ferroptosis signifies a new era in the design of new therapeutic chelation strategies in many other diseases. The introduction of artificial intelligence guidance for optimal chelation therapeutic outcomes in personalised medicine is expected to increase further the impact of chelation in medicine, as well as the survival and quality of life of millions of patients with iron metabolic disorders and also other diseases.

Deferiprone-resveratrol hybrid attenuates iron accumulation, oxidative stress, and antioxidant defenses in iron-loaded human Huh7 hepatic cells.

Chronic liver diseases are complications of thalassemia with iron overload. Iron chelators are required to remove excessive iron, and antioxidants are supplemented to diminish harmful reactive oxygen species (ROS), purposing to ameliorate oxidative liver damage and dysfunctions. The deferiprone-resveratrol hybrid (DFP-RVT) is a synthetic iron chelator possessing anti-β-amyloid peptide aggregation, anti-malarial activity, and hepatoprotection in plasmodium-infected mice. The study focuses on investigating the antioxidant, cytotoxicity, iron-chelating, anti-lipid peroxidation, and antioxidant defense properties of DFP-RVT in iron-loaded human hepatocellular carcinoma (Huh7) cells. In the findings, DFP-RVT dose dependently bound Fe(II) and Fe(III) and exerted stronger ABTS•- and DPPH•-scavenging (IC50 = 8.0 and 164μM, respectively) and anti-RBC hemolytic activities (IC50 = 640μM) than DFP but weaker than RVT (p < 0.01). DFP-RVT was neither toxic to Huh7 cells nor PBMCs. In addition, DFP-RVT diminished the level of redox-active iron (p < 0.01) and decreased the non-heme iron content (p < 0.01) in iron-loaded Huh7 cells effectively when compared without treatment in the order of DFP-RVT > RVT ∼ DFP treatments (50µM each). Moreover, the compound decreased levels of hepatic ROS in a dose-dependent manner and the level of malondialdehyde, which was stronger than DFP but weaker than RVT. Furthermore, DFP-RVT restored the decrease in the GSH content and GPX and SOD activities (p < 0.01) in iron-loaded Huh7 cells in the dose-dependent manner, consistently in the order of RVT > DFP-RVT > DFP. Thus, the DFP-RVT hybrid possesses potent iron chelation, antioxidation, anti-lipid peroxidation, and antioxidant defense against oxidative liver damage under iron overload.

A Critical Review of Methodologies for Evaluating Iron Fertilizers Based on Iron Reduction and Uptake by Strategy I Plants

Under iron (Fe)-limited conditions, plants have developed strategies for acquiring this essential micronutrient. Several Fe sources have been studied as potential fertilizers, with Fe synthetic chelates being the most used to prevent and correct Fe chlorosis in crops. The determination of the activity of the Fe chelate reductase (FCR) enzyme has long been described in the literature to understand the efficiency of Strategy I plants in acquiring Fe from fertilizers under deficient conditions. Other experiments have focused on the translocation of Fe to the plant to define the effectiveness of Fe fertilizers. Yet, both assays are relevant in knowing the capacity of a novel Fe source and other compounds alleviating Fe chlorosis in Strategy I plants. This work reviews the methodologies that are used in FCR assays to evaluate novel Fe fertilizers, including the factors modulating the results obtained for FCR assay activity, such as the Fe substrate, the Fe level during the growing period and during the FCR assay, the pH, the choice of an in vivo or in vitro method, and the plant species. A discussion of the benefits of the concurrence of FCR and Fe uptake assays is then presented alongside a proposed methodology for assessing the effectiveness of Fe fertilizers, emphasizing the importance of understanding chemical and physiological plant interactions. This methodology unifies key factors that modify FCR activity and combines these with the use of the 57Fe tracer to enhance our comprehension of the efficacy of Fe-based fertilizers’ effectiveness in alleviating Fe chlorosis. This comprehensive approach not only contributes to the fundamental understanding of Fe-deficient Strategy I plants but also establishes a robust method for determining the efficiency of novel sources for correcting Fe deficiency in plants.

Influence of synthetic chelators and LMWOAs on the yield and quality attributes of Panicum maximum Jacq. (Poales: Poaceae) in chromium phytoextraction

Phytoextraction is a cost-effective technology for contaminated site remediation. The study was carried out to investigate the potential of Panicum maximum (Jacq.) to remediate Cr-contaminated soil in tannery industries. Using chromium chelators and hyperaccumulating plants (Guinea grass), efforts have been made to decontaminate the chromium-contaminated tannery sites. To evaluate, the pot experiment was conducted, and Guinea grass’s yield and quality parameters were analyzed. The changes in root length, shoot length, and number of tillers were studied for three months, and the maximum values were 12.6 cm, 163.6 cm, and 12.6 cm, respectively, in the treatment with citric acid. The fodder quality parameters such as crude protein (9.2%), crude fibre (27.24%), and green leaf yield (370.3 g/plant) were magnificent in the treatment with citric acid as the chelator. Indeed, maximum hexavalent chromium (2.94 ± 0.06) and total chromium (17.98 ± 0.05) were observed in the citric acid treatment. Among all the treatments analyzed, the low-molecular-weight organic acids (LMWOAs), especially citric acid at 5 mmol/kg, were the best ones that could be recommended for improving the chelating process in the phytoremediation of chromium by Guinea grass. However, among the synthetic chelators, EDTA has resulted in higher chromium chelation and yield attributes such as root length (10.7 cm), shoot length (153.6 cm), number of tillers (10.3), and quality parameters like Guinea grass such as crude protein (8.1%), crude fibre (28.03%), and green leaf yield (342.6 g/plant). The study indicates that the chelators are enhancing Guinea grass growth and incorporating that may assist in the phytoremediation process.

Evaluation of Siderophores Generated by Pseudomonas Bacteria and Their Possible Application as Fe Biofertilizers

The application of synthetic iron chelates to overcome iron deficiency in crops is leading to a high impact on the environment, making it necessary to find more friendly fertilizers. A promising alternative is the application of biodegradable iron chelates, such as those based on siderophores. In the present work, seven bacterial strains of the genus Pseudomonas were selected for their ability to secrete pyoverdine, a siderophore with a high affinity for iron, which could be used as a biofertilizer. The concentration of siderophores secreted by each bacterium expressed as desferrioxamine B equivalents, and the pyoverdine concentration was determined. Their potential as Fe biofertilizers was determined based on their capacity to complex Fe, determining the maximum iron complexation capacity at alkaline pH and selecting the RMC4 strain. The biostimulant capacity of the RMC4 strain was evaluated through the secretion of organic acids such as the hormone Indol-3-acetic acid or glutamic acid, among others, in a kinetic assay. Finally, the genome of RMC4 was determined, and the strain was identified as Pseudomonas monsensis. The annotated genome was screened for genes and gene clusters implicated in biofertilization and plant growth promotion. Besides iron mobilization, genes related to phosphorus solubilization, production of phytohormones and biological control, among others, were observed, indicating the suitability of RMC4 as an inoculant. In conclusion, RMC4 and its siderophores are promising sources for Fe biofertilization in agriculture.

Evaluation of primary and secondary oxidation products in fish oil-in-water emulsions: Effect of metal-complexing peptides and protein hydrolysates

A novel approach consisting of preselection of peptides using bioinformatics tool followed by final selection using Surface Plasmon Resonance (SPR) - an efficient technique to investigate metal complexing properties of peptides/hydrolysates - was developed. Selected pea hydrolysates and synthetic metal chelating peptides potentially present in pea hydrolysates were investigated for their ability to inhibit the lipid oxidation in emulsions composed of 5 % w/w fish oil and stabilized with Tween® 20. Results indicated that addition of peptides/hydrolysates did not impact the physical stability of emulsions and led to lower level of lipid hydroperoxides. Moreover, peptide KGKSR inhibited the generation of 1-penten-3-ol and hexanal to the same level as ethylenediaminetetraacetic acid (EDTA) did and the formation of 2 ethyl-furan was lower than when EDTA was added. Peptide GRHRQKHS showed same concentration of hexanal as EDTA thus confirming efficacy of using SPR for selecting peptides/hydrolysates to use as antioxidants in emulsions.

Electron Paramagnetic Resonance, Electronic Ground State, and Electron Spin Relaxation of Seven Lanthanide Ions Bound to Lanmodulin and the Bioinspired Chelator, 3,4,3-LI(1,2-HOPO).

The electron paramagnetic resonance (EPR) spectra of lanthanide(III) ions besides Gd3+ , bound to small-molecule and protein chelators, are uncharacterized. Here, the EPR properties of 7 lanthanide(III) ions bound to the natural lanthanide-binding protein, lanmodulin (LanM), and the synthetic small-molecule chelator, 3,4,3-LI(1,2-HOPO) ("HOPO"), were systematically investigated. Echo-detected pulsed EPR spectra reveal intense signals from ions for which the normal continuous-wave first-derivative spectra are negligibly different from zero. Spectra of Kramers lanthanide ions Ce3+ , Nd3+ , Sm3+ , Er3+ , and Yb3+ , and non-Kramers Tb3+ and Tm3+ , bound to LanM are more similar to the ions in dilute aqueous:ethanol solution than to those coordinated with HOPO. Lanmodulins from two bacteria, with distinct metal-binding sites, had similar spectra for Tb3+ but different spectra for Nd3+ . Spin echo dephasing rates (1/Tm ) are faster for lanthanides than for most transition metals and limited detection of echoes to temperatures below ~6 to 12 K. Dephasing rates were environment dependent and decreased in the order water:ethanol>LanM>HOPO, which is attributed to decreasing librational motion. These results demonstrate that the EPR spectra and relaxation times of lanthanide(III) ions are sensitive to coordination environment, motivating wider application of these methods for characterization of both small-molecule and biomolecule interactions with lanthanides.

Effect of flaxseed intervention on iron overload and its complications in thalassemia major patients

PurposePhytochemicals are known for their iron chelation ability with no side effects. Lignans and polyphenols in flaxseed have iron-chelating and antioxidant abilities. Therefore, this study aims to assess the ability of flaxseed to reduce iron overload and minimize its negative health effects.Design/methodology/approachA randomized control trial was conducted. A total of 96 patients were enrolled in this study and randomized into three groups: two intervention groups had 3 or 7 g of whole flaxseed and a control group took a placebo (gram seeds). Interventions were administered for 12 weeks. A hematological profile, ferritin quantification in serum, and liver function tests were performed to evaluate the effects of flaxseed.FindingsIt was observed that flaxseed with synthetic iron chelators caused a significant reduction in ferritin levels compared with synthetic chelators. The pre-transfusion hemoglobin level was also improved in the intervention group. A significant reduction (p value 0.0003) in ferritin levels among intervention groups indicated that flaxseed reduced the iron overload. It can be concluded that flaxseed reduced iron overload in thalassemia major patients with no side effects and may reduce iron overload solely when taken in adequate quantity.Originality/valueAlthough the study targets a non-specific protein-ferritin for the evaluation of iron-overload, the initial ferritin value and reduction in these levels indicate the efficacy of ferritin for reducing iron overload in thalassemia major patients. Moreover, this is the first study, to the best of the authors’ knowledge, that demonstrates the iron-chelation ability of flaxseed in thalassemia major patients, suggesting the use of flaxseed for iron chelation.

Antimicrobially effective protein-loaded metal chelated chitosan composite

Abstract The immobilization of lysozyme onto a novel synthetic metal chelator composite based on chitosan/PAA-PMA (chitosan/acrylamide-maleic acid) and its effect on antimicrobial activity were the aim of the current study. The plain composite and the lysozyme immobilized composite were characterized according to scanning electron microscopy (SEM), Ultraviolet spectroscopy (UV), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD) analysis. Furthermore, the activities of lysozyme and immobilized lysozyme were investigated, as well as their antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus, as well as their cytotoxic effects, which were both approximately greater than those of free lysozyme. The last step was cytotoxic studies on lysozyme, chitosan composite, and lysozyme-immobilized chitosan composite, which showed no cytotoxic effect. Several investigations have shown that metal chelators improve lysozyme’s antibacterial action. Two carboxylic acids containing maleic acid were used as a metal chelator in this study. Lysozyme was immobilized from a side other than carboxylic acids, so that carboxylic acid groups, which are metal chelating groups, do not prevent synergy by competing with metal binding at neutral pH. This enhanced antimicrobial activity.

Iron necessity for chlamydospore germination in Fusarium oxysporum f. sp. cubense TR4.

Fusarium wilt disease of banana, caused by the notorious soil-borne pathogen Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4), is extremely difficult to manage. Manipulation of soil pH or application of synthetic iron chelators can suppress the disease through iron starvation, which inhibits the germination of pathogen propagules called chlamydospores. However, the effect of iron starvation on chlamydospore germination is largely unknown. In this study, scanning electron microscopy was used to assemble the developmental sequence of chlamydospore germination and to assess the effect of iron starvation and pH in vitro. Germination occurs in three distinct phenotypic transitions (swelling, polarized growth, outgrowth). Outgrowth, characterized by formation of a single protrusion (germ tube), occurred at 2 to 3h, and a maximum value of 69.3% to 76.7% outgrowth was observed at 8 to 10h after germination induction. Germination exhibited plasticity with pH as over 60% of the chlamydospores formed a germ tube between pH 3 and pH 11. Iron-starved chlamydospores exhibited polarized-growth arrest, characterized by the inability to form a germ tube. Gene expression analysis of rnr1 and rnr2, which encode the iron-dependent enzyme ribonucleotide reductase, showed that rnr2 was upregulated (p < 0.0001) in iron-starved chlamydospores compared to the control. Collectively, these findings suggest that iron andextracellular pH arecrucial for chlamydospore germination in Foc TR4. Moreover, inhibition of germination by iron starvation may be linked to a different mechanism, rather than repression of the function of ribonucleotide reductase, the enzyme that controls growth by regulation of DNA synthesis.

S,S]-EDDS Ligand as a Soil Solubilizer of Fe, Mn, Zn, and Cu to Improve Plant Nutrition in Deficient Soils.

The deficiencies of iron, manganese, zinc, and copper in calcareous soils are a worldwide problem affecting plant growth and fruit quality, usually minimized by the application of recalcitrant synthetic metal chelates. Biodegradable ligand [S,S]-EDDS is an eco-friendly substitute. This study investigates the capacity of [S,S]-EDDS to mobilize micronutrients from agronomic soils and improve plant nutrition. A batch and a plant experiment (Phaseolus vulgaris cv. Black Pole) with three agronomic soils was conducted to monitor the micronutrients solubilized by [S,S]-EDDS, the ligand degradation, and plant uptake. The results demonstrated the high capacity of [S,S]-EDDS to solubilize Fe and other micronutrients related to its chemical behavior and the enhancement of plant nutrition. The best results were shown in sandy-clay soil with low Fe, typically found in the Mediterranean areas. The results support the direct application of the ligand to soils and a possible biotechnological application of the ligand-producer bacteria.

Potential diagnostic biomarkers for lead-induced hepatotoxicity and the role of synthetic chelators and bioactive compounds.

Lead (Pb2+) poisoning is a public health concern of global dimensions. Although several public health guidelines and workplace safety policies are existing and enforced, lead toxicity cases are drastically increasing. Lead exposure leads to numerous harmful consequences and causes adverse effects on different body organs and systems, mainly via the generation of reactive oxygen species, leading to augmented oxidative stress, competing with metal ions, and binding with the sulfhydryl groups. In several instances, lead poisoning cases remain undiagnosed and untreated or receive only symptomatic treatment. Estimation of blood lead levels reflects only a recent exposure, however, which does not reveal the total body burden. This review summarizes the effects of lead with special reference to hepatotoxicity and some of the potential diagnostic biomarkers. Furthermore, it also focuses on synthetic chelators used in the treatment of lead poisoning and the advantage of using bioactive compounds with an emphasis on the ameliorative effect of garlic.

A Review of the Role of Curcumin in Metal Induced Toxicity.

Metal toxicity poses a potential global threat to the environment and living beings. Their numerous agricultural, medical, industrial, domestic, and technological applications result in widespread distribution in the environment which raises concern on the potential effects of metals in terms of health hazards and environmental pollution. Chelation therapy has been the preferred medical treatment for metal poisoning. The chelating agent bounds metal ions to form complex cyclic structures known as 'chelates' to intensify their excretion from the body. The main disadvantage of synthetic chelators is that the chelation process removes vital nutrients along with toxic metals. Natural compounds are widely available, economical, and have minimal adverse effects compared to classical chelators. Herbal preparations can bind to the metal, reduce its absorption in the intestines, and facilitate excretion from the body. Curcumin, a bioactive substance in turmeric, is widely used as a dietary supplement. Most studies have shown that curcumin protects against metal-induced lipid peroxidation and mitigates adverse effects on the antioxidant system. This review article provides an analysis to show that curcumin imparts promising metal toxicity-ameliorative effects that are related to its intrinsic antioxidant activity.

Iron nutrition in agriculture: From synthetic chelates to biochelates

Iron (Fe) is an essential micronutrient for plant growth and productivity and, among other micronutrients, is the one required in higher amounts. In most soils, Fe occurs at relatively high concentrations; nevertheless, in calcareous soils, Fe bioavailability can be very limited, thus leading plants to develop Fe deficiency symptoms. At present, Fe fertilization still represents the most frequent approach adopted in agriculture to prevent or remediate Fe chlorosis. For soil applications, Fe fertilizers are based on Fe chelated with aminocarboxylate synthetic ligands (e.g. HEDTA, EDTA, DTPA, EDDHA), which are effective in maintaining Fe in the soil solution, even in alkaline soils, and thus in increasing its bioavailability for plant uptake. Nevertheless, Fe-aminocarboxylate complexes presents some limitations, related for instance to pH-dependent effectiveness, stability, persistence in the environment and ligand exchange reactions. In this context, vegetal-derived protein hydrolysates might represent good sources of biochelating ligands for developing innovative Fe fertilizers for sustainable agriculture. Protein hydrolysates are composed by small peptides, which, on one hand, can chelate Fe via amino acid side chains, carboxylate groups of C-termini, amine groups of N-termini and N atoms of amide groups of the peptide backbone, whilst, on the other hand, small peptides can also play a signaling role, triggering the acquisition of nutrient and morphogenetic processes in plants. The present paper reviews the current state of knowledge on traditional Fe fertilizers and, on the other side, explores the possible advantages in the application of biochelates as innovative Fe fertilizers. To further corroborate the hypothesis, three experimental trials have been carried out on three horticultural crops (cucumber, tomato, and strawberry) using a Fe-biochelate as Fe source and comparing it with the widely used traditional synthetic chelate Fe-EDDHA. The results in the three crops clearly show that Fe-biochelate is, at least, as efficient as Fe-EDDHA as source of micronutrient, even under circumneutral (pH 6.0) and alkaline conditions (pH 8.0), thus proving that Fe-biochelates can be promising alternatives to synthetic Fe chelates for the Fe nutrition management of crops. Considering the potential drawbacks of synthetic chelates (e.g., leachability, persistence, remobilization of toxic metals in soil), these findings might contribute enhancing the agriculture sustainability. In addition, Fe-biochelate could also find an application in soilless cultivation systems as an alternative to synthetic Fe chelates for Fe enrichment of edible plant tissues (biofortification), increasing their nutritional value.

Synthesis and characterization of the Schiff base Fe(II) complex as a new iron source in nutrient solution

Supplying available iron (Fe) for plant growth in hydroponic nutrient solutions is a great challenge. The chelators commonly used to supply Fe in nutrient solutions have several disadvantages such as the production of photodegradable compounds and may negatively affect plant growth by toxic side effects on plants and impaired micronutrient balance. PurposeIn this study, a new complex of Fe(II)-triethylenetetramine di salicylaldehyde (Fe-TETDSA) was synthesized and applied to a nutrient solution. MethodsFe-TETDSA was synthesized by the traditional Schiff base prepration method and characterized by FT-IR, Raman, UV–Vis, photoluminescence, molar conductivity and elemental analysis. Fe-TETDSA (with single and double dose) was evaluated as a new Fe source for corns grown in nutrient solution compared to the Fe-EDTA and Fe-EDDHA, as well as FeSO4. ResultsThe Fe-TETDSA was stable in alkaline pH. Application of Fe-TETDSA chelate significantly increased root and shoot dry weight corns compared to Fe-EDTA and Fe-EDDHA. The total Fe concentration of plants supplied with Fe-TETDSA was more than those supplied with Fe-TETDSA2 and Fe-EDDHA. . Corn plants treated with Fe-TETDSA chelates also accumulated significantly higher levels of Zn (zinc) and N (nitrogen) in their shoots compared with those treated with Fe-EDTA and Fe-EDDHA. But the application of Fe-TETDSA (single and double dose) decreased Cu and Mn concentration in corns shoot. Application of Fe-TETDSA, Fe-TETDSA2 and Fe-EDDHA showed the highest SPAD index in corns leaves. ConclusionsThe results showed that Fe-TETDSA may be a sustainable alternative to traditional synthetic chelating agents such as EDTA or EDDHA in nutrient solution.

Arsenic-induced toxicity and the ameliorative role of antioxidants and natural compounds.

Arsenic (As) poisoning has proven to be a major threat worldwide because of its toxic effects on the human body. As toxicity through drinking water is a global health concern. The toxicity of As is known to affect the liver, kidney, lungs, muscles, cardiovascular system, and nervous system and can even induce diabetes. Further As can cause skin lesions leading to notable diseases in the skin like Bowen's disease. Chronic exposure to As has caused many tragedies in Eastern, and several Southeast Asian and Latin American countries. Long-term exposure to As makes it an immediate threat that should be dealt with as a priority, and one of the ways to handle it may be with the use of antioxidants. In this review, we have discussed the natural and anthropogenic sources of As, its metabolism, pathophysiology, and mechanism of toxicity. Besides, we have also discussed some of the synthetic chelators and the ameliorative role of antioxidants and natural compounds in reducing As toxicity.