Effects Of Metal Ion Chelation Research Articles

Eucalyptus globulus Essential Oil as a Natural Food Preservative: Antioxidant, Antibacterial and Antifungal Properties In Vitro and in a Real Food Matrix (Orangina Fruit Juice)

The potential application of Eucalyptus globulus essential oil (EGEO) as a natural beverage preservative is described in this research. The chemical composition of EGEO was determined using gas chromatography analyses and revealed that the major constituent is 1,8-cineole (94.03% ± 0.23%). The in vitro antioxidant property of EGEO was assessed using different tests. Percentage inhibitions of EGEO were dose-dependent. In addition, EGEO had a better metal ion chelating effect with an IC50 value of 8.43 ± 0.03 mg/mL, compared to ascorbic acid (140.99 ± 3.13 mg/mL). The in vitro antimicrobial effect of EGEO was assessed against 17 food spoilage microorganisms. The diameter of the inhibitory zone (DIZ) ranged from 15 to 85 mm for Gram-positive bacteria and from 10 to 49 mm for yeast strains. Candida albicans, C.parapsilosis and Saccharomyces cerevisiae were the most sensitive fungal species to the EGEO vapor with DIZ varying from 59 to 85 mm. The anti-yeast effectiveness of EGEO alone and in association with heat processing was estimated in a real juice matrix (Orangina fruit juices) in a time-dependent manner. The combination of EGEO-heat treatment (70 °C for 2 min) at different concentrations (0.8 to 4 µL/mL) was effective at reducing S. cerevisiae growth in the fruit juice of Orangina, compared to juice preserved with synthetic preservatives. Current findings suggest EGEO as an effective and potent inhibitor of food spoilage fungi in a real Orangina juice, and might be a potential natural source of preservative for the food industry.

Inhibition of urease activity by different compounds provides insight into the modulation and association of bacterial nickel import and ureolysis

The nickel-dependent urease enzyme is responsible for the hydrolysis of urea to ammonia and carbon dioxide. A number of bacteria produce urease (ureolytic bacteria) and are associated with various infectious diseases and ammonia emissions from agriculture. We report the first comprehensive comparison of the inhibition of urease activity by compounds analysed under the same conditions. Thus, 71 commercially available compounds were screened for their anti-ureolytic properties against both the ureolytic bacterium Klebsiella pneumoniae and purified jack bean urease. Of the tested compounds, 30 showed more than 25% inhibition of the ureolytic activity of Klebsiella pneumoniae or jack bean urease, and among these, carbon disulfide, N-phenylmaleimide, diethylenetriaminepentaacetic acid, sodium pyrrolidinedithiocarbamate, 1,2,4-butanetricarboxylic acid, tannic acid, and gallic acid have not previously been reported to possess anti-ureolytic properties. The diverse effects of metal ion chelators on ureolysis were investigated using a cellular nickel uptake assay. Ethylenediaminetetraacetic acid (EDTA) and dimethylglyoxime (DMG) clearly reduced the nickel import and ureolytic activity of cells, oxalic acid stimulated nickel import but reduced the ureolytic activity of cells, 1,2,4-butanetricarboxylic acid strongly stimulated nickel import and slightly increased the ureolytic activity of cells, while L-cysteine had no effect on nickel import but efficiently reduced the ureolytic activity of cells.

Antioxidant potential of Sargassum horneri extract against urban particulate matter-induced oxidation.

Particulate matter is a major contribution of air pollution and detrimental to human health. The in vitro antioxidant activities of a brown seaweed, Sargassum horneri ethanol extract (SHE) against particulate matter-induced oxidative stress were investigated by measuring 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging activity, hydrogen peroxide (H2O2) scavenging activity, superoxide anion (O2 ·-) inhibition, hydroxyl radical ( · OH) scavenging activity, reducing power, and the metal ion-chelating effect. All in vitro antioxidant activities were increased as the concentration of SHE increased (0-1000μg/mL). When treated with particulate matter at 0-1000μg/mL, the DPPH free radical, and H2O2 scavenging activities, reducing power, and metal ion-chelating abilities of SHE were significantly decreased (p < 0.05). These results indicate that Sargassum horneri, which is a rich source of bioactive compounds, can be used as a natural source of antioxidants in the food industries.

Intercomparative investigation of the total phenols, total flavonoids, In vitro and In vivo antioxidant activities of capparis Cartilaginea (Decne.) maire and weiller and Capparis Ovata Desf. from Jordan

Background: Plant-derived antioxidants have been products of choice in therapeutic formulations for their potent free radical scavenging activity and mitigating and curing illnesses and diseases associated with oxidative stress. Capparis L. includes species with unprecedented nutritional and medicinal values, and hence offers a diverse pool of phytochemicals implicated in antioxidant activity. Objective: The current study was designed to assess the chemical variation, total phenols content (TPC), total flavonoids content (TFC), in vitro and in vivo antioxidant activities of different extracts obtained from Capparis cartilaginea and Capparis ovata from Jordan. Materials and Methods: The ethanolic extract from each species was partitioned in different solvents and the TPC, TFC, and antioxidant activity for each extract was examined. The in vitro antioxidant activities were tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azino–bis (3-ethylbenzoline-6-sulfonic acid diammonium salt (ABTS) radical scavenging methods in addition to the metal ion chelating effect (MCE) and hydroxyl radical assay methods. The butanol extract was investigated for its in vivo effect on the activities of serum superoxide dismutase (SOD) and glutathione peroxidase (GPX) in mice (100 mg/kg, intraperitoneally for 12 days). Results: The butanol fraction of both plants had a dose-dependent in vitro antioxidant activity. The treatment of mice with the butanol extract of both species for 12 days significantly increased the activities of serum SOD and GPX. Principal component analysis indicated that DPPH, TFC, hydroxyl radical had major variability in the antioxidant activities of the two investigated Capparis species. Results of this study underscores enrichment of the two studied Capparis species with phenolics and flavonoids that could account for much of their antioxidant activities. Abbreviations used: C. cartilaginea: Capparis cartilaginea ; C. ovata: Capparis ovata; TPC: Total phenols content; TFC: Total flavonoids content; DPPH: 2,2-diphenyl-1-picrylhydrazyl; ABTS: 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid; MC: Metal Chelating effect; Hydroxy: Hydroxyl radical assay; SOD: Serum superoxide dismutase; GPX: Glutathione Peroxidase ;PC: Principal Component.

Evaluation of antioxidant activities and chemical analysis of sulfated chitosan from Sepia prashadi

The chitin and chitosan of S. prashadi was prepared through demineralization, deproteinzation, deacetylation process and sulfation were carried by chlorosulfonic acid in N,N-dimethylformamide. The sulfate content in chitosan was found to be 18.9%. The carbon, hydrogen and nitrogen composition of the sulfated chitosan were recorded 39.09%, 6.95% and 6.58% respectively. The structural analysis was done by using FT-IR and NMR spectroscopy technique. The DSC curves of sulfated chitosan showed a large endothermic peak resolved with To value of 54.57°C and TP value of 97.46°C. The morphology of sulfated chitin and sulfated chitosan were studied by SEM. The Further in vitro antioxidant activity of sulfated chitosan was screened by scavenging activity of superoxide radical assay, hydroxyl radical scavenging assay, metal-ion chelating effect and reducing power. Its anticoagulant activity was tested for human plasma with respect to Activated Partial Thromboplastin Time (APTT) and Prothrombin Time (PT). Results prove that sulfated chitosan has potent antioxidant and anticoagulant activity.

Antioxidant Contents and Antioxidant Activities of White and Colored Potatoes (Solanum tuberosum L.).

This study was performed to evaluate and compare the antioxidant substance content and antioxidant activities of white (Superior) and colored (Hongyoung, Jayoung, Jasim, Seohong, and Jaseo) potatoes. The potatoes were extracted with 80% ethanol and were evaluated for the total polyphenol, flavonoid, and anthocyanin contents and for 1,1-diphenyl- 2-picrylhydrazyl (DPPH)/2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activity, reducing power, and ferrous metal ion chelating effect. The total polyphenol, flavonoid, and anthocyanin contents of Hongyoung and Jayoung were higher than white and other colored potatoes. All colored potato extracts, except for Jaseo and Seohong, showed higher ABTS radical scavenging activities than the general white potato extract. Hongyoung and Jayoung had the highest ABTS and DPPH radical scavenging activities. Optical density values for the reducing power of Jayoung and Jaseo at concentration of 2 mg/mL were 0.148 and 0.090, respectively. All colored potato extracts had lower ferrous metal ion chelating effect than the white potato. A significant (P<0.05) positive correlation was observed between total polyphenol content and total flavonoid content (r=0.919), anthocyanin content (r=0.992), and ABTS radical scavenging activity (r=0.897). Based on these results, this research may be useful in developing the Hongyoung and Jayoung cultivars with high antioxidant activities.

Blood glucose lowering effect of Tridax procumbens in type 2 diabetes may be attributed to AMPK activation and suppression of hepatic gluconeogenesis (259.8)

Traditional knowledge and anecdotal evidence suggest that Tridax procumbens Linn may have anti‐inflammatory and blood glucose lowering properties. Recent studies have shown that T.procumbens extract was effective in lowering blood glucose (42‐71% blood glucose reduction at 250‐500 mg/kg body weight) in alloxan‐induced diabetic rats. The goals of this study were to evaluate blood glucose lowering potential of T.procumbens extract in subjects with type 2 diabetes and characterize underlying molecular mechanisms. Twenty individuals with established type 2 diabetes were orally administered (15 ml, twice daily) T.procumbens extract, prepared according to Ayurveda guidelines, for a period of 4 weeks. Fasting blood glucose concentrations were reduced by 11% in men and 20% in women, and post‐prandial blood glucose concentrations were decreased by 26% in men and 29% in women. No adverse effects were reported by the participants. Chemical and microbial analyses of T. procumbens extract demonstrated the presence of phenolics, carotenoids, and flavonoids, and absence of microbial contaminants, aflatoxins, and heavy metals. T.procumbens extract demonstrated strong antioxidant potential and anti‐inflammatory activity as evidenced through Trolox equivalent antioxidant capacity, ferric‐ion reducing potential, hydrogen peroxide scavenging activity, and metal ion chelating effect in vitro, and inhibition of NFκB and IkBα in LPS‐stimulated RAW 264.7 murine macrophages. T.procumbens extract significantly increased AMPK activation and suppressed dexamethasone‐induced PEPCK and G6Pase gene expression with subsequent decrease in hepatic glucose production in H4IIE cells. Our studies indicate that T.procumbens extract exhibits strong antioxidant and anti‐inflammatory properties. Activation of AMPK and suppression of hepatic glucose production may be one mechanism that contributes to the glucose‐lowering property of T. procumbens.Grant Funding Source: Diabetes Action Research and Education Foundation

Aldose reductase and the importance of experimental design.

Kinetic studies on the AR (aldose reductase) protein have shown that it does not behave as a classical enzyme in relation to ring aldose sugars. As with non-enzymatic glycation reactions, there is probably a free-radical element involved derived from monosaccharide autoxidation. In the case of AR, there is free radical oxidation of NADPH by autoxidizing monosaccharides, which is enhanced in the presence of the NADPH-binding protein. Thus any assay for AR based on the oxidation of NADPH in the presence of autoxidizing monosaccharides is invalid, and tissue AR measurements based on this method are also invalid, and should be reassessed. AR exhibits broad specificity for both hydrophilic and hydrophobic aldehydes that suggests that the protein may be involved in detoxification. The last thing we would want to do is to inhibit it. ARIs (AR inhibitors) have a number of actions in the cell which are not specific, and which do not involve them binding to AR. These include peroxy-radical scavenging and effects of metal ion chelation. The AR/ARI story emphasizes the importance of correct experimental design in all biocatalytic experiments. Developing the use of Bayesian utility functions, we have used a systematic method to identify the optimum experimental designs for a number of kinetic model data sets. This has led to the identification of trends between kinetic model types, sets of design rules and the key conclusion that such designs should be based on some prior knowledge of K (m) and/or the kinetic model. We suggest an optimal and iterative method for selecting features of the design such as the substrate range, number of measurements and choice of intermediate points. The final design collects data suitable for accurate modelling and analysis and minimizes the error in the parameters estimated, and is suitable for simple or complex steady-state models.

Structure and chemistry of N-substituted corroles and their rhodium(I) and zinc(II) metal-ion complexes.

In the present work we report on the detailed structural features of the chiral N21- and N22-substituted benzyl and picolyl derivatives of tris(pentafluorophenyl)corrole [H3(tpfc)]. The main difference between the isomers is that substitution on N22 creates a much more crowded environment, reflected in higher deformation of the corrole ring from planarity and of the meso-aryls from perpendicular orientation. The effects of metal-ion chelation on corrole geometry are demonstrated by structural investigations of the zinc(II) and rhodium(I) complexes of the N21- and N22-alkylated corroles. The major finding is the intramolecular coordination of the pyridine moiety of the picolyl substituent in the case of [ZnII(N21-picolyl-tpfc)]. This pyridine is readily attracted to the zinc ion as an axial ligand, thus replacing the external pyridine molecule of the precursor [ZnII(N21-benzyl-tpfc)(py)]. The change is associated with a considerable flattening of the corrole ring in order to allow a more convenient coordination of the zinc ion to all four pyrrole nitrogen atoms (at Zn-N(pyr-role) distances of 1.956-1.987 A for the nonsubstituted sites, and 2.224-2.247 A for the substituted sites). These structural investigations also aid a good understanding of the spectroscopic characteristics of the derivatives.

Novel Effects of Metal Ion Chelation on the Properties of Lipoic Acid-Capped Ag and Au Nanoparticles

The effects of the interactions of metal ions with lipoic acid-capped Ag and Au nanoparticles have been studied by the combined use of electronic absorption spectroscopy and transmission electron microscopy. Three types of effects that are dependent on the metal ion concentration can be distinguished. First, in the dilute regime, there is reversible chelation of the metal ions, causing a marked dampening of the plasmon resonance band of the nanoparticles, but there is no aggregation. The magnitude of plasmon dampening depends on the nature as well as the concentration of the metal ions. In the intermediate concentration regime, aggregation occurs, but in the high concentration regime, there is precipitation. These different regimes are clearly evidenced in the changes in the electronic spectra and in the electron micrographs.

Ionochromic Effects and Structures of Metalated Poly(p-phenylenevinylene) Polymers Incorporating 2,2‘-Bipyridines

The effects of metal ion chelation to the 2,2‘-bipyridine (bpy) groups on the photophysics and exciton dynamics of two conjugated polymers 1 and 2 in solution are investigated. The structures of polymers 1 and 2 have 2,2‘-bipyridyl-5-vinylene units that alternate with one and three 2,5-bis(n-decyloxy)-1,4-phenylenevinylene monomer units, respectively. The photophysics and exciton dynamics of metalated polymers 1 and 2 are compared to those of the metal-free polymers (Chen et al. J. Phys. Chem. A 1999, 103, 4341−4351). The origins of ionochromic effects due the metal ion chelation were studied using both steady-state and transient optical spectroscopy, and the results indicate that both conformational flattening and participation of π electrons from the metal in the π-conjugation of the polymer backbone play important roles in metal ion binding induced red shifts in absorption and photoluminescence spectra. The photoluminescence properties of the metalated polymers are determined by the metal ion electronic structures, where the closed shell Zn2+-bound polymer 2 has an increased photoluminescence quantum yield and the corresponding open shell Ni2+- or Fe3+-bound polymers have quenched photoluminescence due to spin−orbit coupling. The dual character of metalated polymer 2 as a conjugated polymer and as a metal−bpy complex is discussed. In addition, the structures of metal ion binding sites are studied via X-ray absorption fine structure (XAFS) and are related to the photophysical properties of the metalated polymers.

Aldose reductase: a window to the treatment of diabetic complications?

Kinetic studies on the aldose reductase protein (AR2) have shown that it does not behave as a classical enzyme in relation to ring aldose sugars. These results have been confirmed by X-ray crystallography studies, which have pinpointed binding sites for pharmacological "aklose reductase inhibitors" (ARIs). As with non-enzymic glycation reactions, there is probably a free-radical element involved derived from monosaccharide autoxidation. In the case of AR2, there is free radical oxidation of NADPH by autoxidising monosaccharides, enhanced in the presence of the NADPH-binding protein. Whatever the behaviour of AR2, many studies have showed that sorbitol production is not an initiating aetiological factor in the development of diabetic complications in humans. Vitamin E (alpha-tocopherol), other antioxidants and high fat diets can delay or prevent cataract in diabetic animals even though sorbitol and fructose levels are not modified; vitamin C acts as an AR1 in humans. Protein post-translational modification by glyc-oxidation or other events is probably the key factor in the aetiology of diabetic complications. There is now no need to invoke AR2 in xylitol biosynthesis. Xylitol can be produced in the lens from glucose, via a pathway involving the enzymes myo-inositol-oxygen oxidoreductase, D-glucuronate reductase. L-gulonate NAD(+)-3-oxidoreductase and L-iditol-NAD(+)-5-oxidoreductase, all of which have recently been found in bovine and rat lens. This chapter investigates the molecular events underlying AR2 and its binding and kinetics. Induction of the protein by osmotic response elements is discussed, with detailed analysis of recent in vitro and in vivo experiments on numerous ARIs. These have a number of actions in the cell which are not specific, and which do not involve them binding to AR2. These include peroxy-radical scavenging and recently discovered effects of metal ion chelation. In controlled experiments, it has been found that incubation of rat lens homogenate with glucose and the copper chelator o-phenanthroline abolishes production of sorbitol. Taken together, these results suggest AR2 is a vestigial NADPH-binding protein, perhaps similar in function to a number of non-mammalian crystallins which have been recruited into the lens. There is mounting evidence for the binding of reactive aldehyde moieties to the protein, and the involvement of AR2 either as a 'housekeeping' protein, or in a free-radial-mediated 'catalytic' role. Interfering with the NADPH binding and flux levels--possibly involving free radicals and metal ions--has a deleterious effect. We have yet to determine whether aldose reductase is the black sheep of the aldehyde reductase family, or whether it is a skeleton in the cupboard, waiting to be clothed in the flesh of new revelations in the interactions between proteins, metal ions and redox metabolites.

34] Distinguishing reactivities of peroxynitrite and hydroxyl radical

Publisher Summary This chapter discusses the distinguishing reactivities of peroxynitrite and hydroxyl radical. The oxidations using peroxynitrite prepared by independent methods afford the same yields of ethylene and methionine sulfoxide from methionine. The presence of metal ion chelators such as ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) does not affect these yields, suggesting that trace amounts of metal ions are not involved in these processes when the peroxynitrite is treated with MnO2 to destroy the hydrogen peroxide, or when a hydrogen peroxide free preparation is selected. Ethylene is formed from both the reactions of methionine with peroxynitrite and the hydroxyl radical. The yield of ethylene from the reaction of methionine with peroxynitrite is not affected by hydroxyl radical scavengers that do not react with ground-state peroxynitrous acid (HOONO). These data suggest that peroxynitrite oxidations involve ground-state HOONO and/or excited-state peroxynitrous acid (HOONO*) but not hydroxyl radicals. The effects of metal ion chelators that either exacerbate or inhibit Fenton-type reactions on oxidations by peroxynitrite are also reviewed in the chapter.

Generation of 5,5-Dimethyl-1-pyrrolineN-Oxide Hydroxyl and Scavenger Radical Adducts from Copper/H2O2Mixtures: Effects of Metal Ion Chelation and the Search for High-Valent Metal–Oxygen Intermediates

A metal-catalyzed nucleophilic addition mechanism for the formation of radical adducts of the spin trap 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) has been described recently (K. Makino, T. Hagiwara, A. Hagi, M. Nishi, and A. Murakami, 1990,Biochem. Biophys. Res. Commun.172, 1073–1080; P. M. Hanna, W. Chamulitrat, and R. P. Mason, 1992,Arch. Biochem. Biophys.296, 640–644). In the present investigation, we have demonstrated that the recently reported inhibition of copper-dependent hydroxyl radical formation by the complexing agent 1,10-phenanthroline (OP), which appears to contradict the well-known chemical nuclease properties of CuI(OP)2, is an artifact resulting from an inhibition of the nucleophilic addition of water to DMPO by OP (A. C. Mello-Filho and R. Meneghini, 1991,Mutat. Res.251, 109–113). Copper bound to OP was found to be a good catalyst of hydroxyl radical formation: the CuII(OP)2complex can be reduced by H2O2and the CuI(OP)2generated reacts with the peroxide to form[formula]In contrast, no evidence could be obtained for oxidant formation from the[formula]reaction system, despite the detection of a prominent signal from the DMPO hydroxyl radical adduct (DMPO/[formula](the formation of which was due solely to the nucleophilic addition of water to DMPO). The failure to generate an oxidant in this reaction mixture was attributed to the failure of hydrogen peroxide to reduce[formula]as hydroxyl radical formation did occur when[formula]was added directly to H2O2. However, in order to account for the high concentration of α-hydroxyethanol radi cals detected when ethanol was included in the[formula]reaction, the possibility that an oxidant in addition to[formula](e.g., CuO+) is generated is discussed.

Effects of metal ion chelators on DNA strand breaks and inactivation produced by hydrogen peroxide in Escherichia coli: detection of iron-independent lesions

In order to study the role of metallic ions in the H2O2 inactivation of Escherichia coli cells, H2O2-sensitive mutants were treated with metal ion chelators and then submitted to H2O2 treatment. o-Phenanthroline, dipyridyl, desferrioxamine, and neocuproine were used as metal chelators. Cell sensitivity to H2O2 treatment was not modified by neocuproine, suggesting that copper has a minor role in OH production in E. coli. On the other hand, prior treatment with iron chelators protected the cells against the H2O2 lethal effect, indicating that iron participates in the production of OH. However, analysis of DNA sedimentation profiles and DNA degradation studies indicated that these chelators did not completely block the formation of DNA single-strand breaks by H2O2 treatment. Thiourea, a scavenger of OH, caused a reduction in both H2O2 sensitivity and DNA single-strand break production. The breaks observed after treatment with metal chelators and H2O2 were repaired 60 min after H2O2 elimination in xthA but not polA mutant cells. Therefore, we propose that there are at least two pathways for H2O2-induced DNA lesions: one produced by H2O2 through iron oxidation and OH production, in which lesions are repaired by the products of the xthA and polA genes, and the other produced by an iron-independent pathway in which DNA repair requires polA gene products but not those of the xthA gene.

Detection of peroxyl and alkoxyl radicals produced by reaction of hydroperoxides with rat liver microsomal fractions.

E.s.r. spin trapping using the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was used to detect peroxyl, alkoxyl and carbon-centred radicals produced by reaction of t-butyl hydroperoxide (tBuOOH) with rat liver microsomal fraction. The similarity of the hyperfine coupling constants of the peroxyl and alkoxyl radical adducts to those obtained previously with isolated enzymes suggests that these species are the tBuOO. and tBuO. adducts. The effects of metal-ion chelators, heat denaturation, enzyme inhibitors and reducing equivalents demonstrate that these species arise from reaction of tBuOOH with a haem enzyme such as cytochrome P-450 or cytochrome b5. In the absence of NADPH or NADH the previously undetected peroxyl radical adduct is the major species observed. In the presence of these reducing equivalents the alkoxyl and carbon-centred radical adducts predominate, which is in accord with product studies on similar systems. These results demonstrate that both reductive and oxidative decomposition of tBuOOH can occur in rat liver microsomal fraction with the reductive pathway favoured in the presence of NADH or NADPH.