Oxidation Of Ascorbate Research Articles

A Stabilizing Agent, PCA/DTPA, Improves Plasma Storage Life for the Chromsystems Vitamin C Assay up to Six Months.

The commonly used Chromsystems vitamin C (ascorbate) assay (Munich, Germany) has a sample storage life of five days at -20°C. Stabilizing agents have been successfully used to increase longevity; however, their suitability with this commercial assay is unclear. We investigated the compatibility of a stabilizing agent, perchloric acid/diethylenetriaminepentaacetic acid (PCA/DTPA), with the Chromsystems assay. Plasma was stored at -80°C, with or without PCA/DTPA. Storage up to six months was assessed through baseline and repeat analyses, stability was assessed by comparing paired non-stabilized and PCA/DTPA-stabilized plasma, and performance was assessed using allowable performance specifications of an external quality assurance program. Ascorbate concentration was significantly lower in non-stabilized plasma than in paired PCA/DTPA-stabilized plasma, with a proportional difference of 11% (P=0.01). All storage analysis results were within the allowable performance specifications. Storage at -80°C prevented plasma ascorbate oxidation; however, substantial oxidation occurred during sample processing. In conclusion, PCA/DTPA significantly reduces ascorbate oxidation, and PCA/DTPA-stabilized ascorbate plasma is compatible with the Chromsystems assay and stable for up to six months, when stored at -80°C.

Voltammetric Determination of Ascorbic Acid in Pharmaceutical Formulations Using Modified Iodine-Coated Platinum Electrode

Background: Despite the high reactivity of the platinum electrode, the iodine-coated platinum electrode shows obvious inertness toward adsorption and surface processes. For that, iodine-coated platinum electrodes accommodate themselves to interesting voltammetric applications. Objectives: This study reports using the modified iodine-coated polycrystalline platinum electrode as a voltammetric sensor for ascorbic acid determination in pharmaceutical formulations. Methods: The developed voltammetric method based on recording cyclic voltammograms of ascorbic acid at iodine-coated electrode The optimized experimental parameters for the determination of ascorbic acid were using 0.1 M KCl as a supporting electrolyte with a scan rate of 50mV/s. Results: The anodic peak related to ascorbic acid oxidation was centered at nearly 0.28V. An excellent and extended linear dependence of the oxidative peak current on the concentration of ascorbic acid was observed in the range 2.84x10-3 - 5.68 mM. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.0 µM and 3.01 µM, respectively, attesting to the method’s sensitivity. The investigation for the effect of potential interference from multivitamin tablet ingredients (vitamins B1, B6, B12, folic acid, citric acid, sucrose, glucose, and zinc) indicated specific selectivity toward ascorbic acid and the absence of any electrochemical response toward these components. Recovery results in the range 98.93±2.78 - 99.98±5.20 for spiked standard ascorbic acid in pharmaceutical formulations further confirmed the potential applicability of the developed method for the determination of ascorbic acid in real samples. Conclusions: The developed method was successfully applied to the analysis of ascorbic acid (vitamin C), and the obtained results were in good agreement with the labeled values; besides, the statistical tests indicated no significant difference at p=0.05 with a 95% confidence level.

Christmas‐Tree‐Shaped Palladium Nanostructures Decorated on Glassy Carbon Electrode for Ascorbic Acid Oxidation in Alkaline Condition

AbstractChristmas‐tree‐shaped Pd nanostructures were synthesized using a simple one‐step electrodeposition method with no additives on a glassy carbon electrode (GCE) surface. Growth of the hierarchical nanostructures was optimized through the applied potential, deposition time, and precursor concentration. Comprehensive characterization techniques such as scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray photoelectron spectroscopy (XPS), X‐ray powder diffraction (XRD), and cyclic voltammetry (CV) were used to characterize structural features of the Christmas‐tree‐shaped Pd nanostructures. Our Christmas‐tree‐shaped Pd nanostructures showed excellent catalytic activity for ascorbic acid (AA) electro‐oxidation in the alkaline condition. The modified electrode exhibited current density of 4.5 mA cm−2: much higher than that of unmodified GCE (0.6 mA cm−2). This simple electrodeposition technique with well‐defined hierarchical Pd nanostructures is expected to offer new perspectives using Pd‐based nanostructured surfaces in different research areas.

Inversion of the Photogalvanic Effect of Conductive Polymers by Porphyrin Dopants

Conductive polymers are widely used as active and auxiliary materials for organic photovoltaic cells due to their easily tunable properties, high electronic conductivity, and light absorption. Several conductive polymers show the cathodic photogalvanic effect in pristine state. Recently, photoelectrochemical oxygen reduction has been demonstrated for nickel complexes of Salen-type ligands. Herein, we report an unexpected inversion of the photogalvanic effect caused by doping of the NiSalen polymers with anionic porphyrins. The observed effect was studied by means of UV-Vis spectroscopy, cyclic voltammetry and chopped light chronoamperometry. While pristine NiSalens exhibit cathodic photopolarization, doping with porphyrins inverts the polarization. As a result, photoelectrochemical oxidation of the ascorbate proceeds smoothly on the NiSalen electrode doped with zinc porphyrins. The highest photocurrents were observed on NiSalen polymer with o-phenylene imine bridge, doped with anionic zinc porphyrin. Assuming this, porphyrin serves both as a catalytic center for the oxidation of ascorbate and an internal electron donor, facilitating the photoinduced charge transport and anodic depolarization.

Copper binding and reactivity at the histidine brace motif: insights from mutational analysis of the Pseudomonas fluorescens copper chaperone CopC.

The histidine brace (His-brace) is a copper-binding motif that is associated with both oxidative enzymes and proteinaceous copper chaperones. Here, we used biochemical and structural methods to characterize mutants of a His-brace-containing copper chaperone from Pseudomonasfluorescens (PfCopC). A total of 15 amino acid variants in primary and second-sphere residues were produced and characterized in terms of their copper binding and redox properties. PfCopC has a very high affinity for Cu(II) and also binds Cu(I). A high reorganization barrier likely prevents redox cycling and, thus, catalysis. In contrast, mutations in the conserved second-sphere Glu27 enable slow oxidation of ascorbate. The crystal structure of the variant E27A confirmed copper binding at the His-brace. Unexpectedly, Asp83 at the equatorial position was shown to be indispensable for Cu(II) binding in the His-brace of PfCopC. A PfCopC mutant that was designed to mimic the His-brace from lytic polysaccharide monooxygenase-like family X325 did not bind Cu(II), but was still able to bind Cu(I). These results highlight the importance of the proteinaceous environment around the copper His-brace for reactivity and, thus, the difference between enzyme and chaperone.

Bis(8‐hydroxyquinoline) Ligands: Exploring their Potential as Selective Copper‐Binding Agents for Alzheimer's Disease

AbstractAmyloid‐β (Aβ) aggregation, metal ion dyshomeostasis, and oxidative stress are pathological features of Alzheimer's disease (AD). Aβ and metal ions form metal‐Aβ complex species that influence the aggregation of Aβ and, in particular, redox metal ions such as Cu lead to the production of reactive oxygen species (ROS). To target metal coordination to Aβ and the reactivities of Cu−Aβ, metal chelating agents must extract Cu2+ from Aβ in AD pathological conditions. Bis(8‐hydroxyquinoline) ligands can extract Cu2+ from Aβ and therefore inhibit the Cu‐induced Aβ aggregation and the aerobic oxidation of ascorbate. In particular, N‐butyl‐2,2‐imino‐bis(8‐hydroxyquinoline) can selectively target Cu−Aβ reactivities in the presence of Zn2+ such as in AD brain patients. The ligands can release Cu in intracellular environments in the presence of a large excess of glutathione, contributing to restore Cu homeostasis.

Ascorbate oxidation by iron, copper and reactive oxygen species: review, model development, and derivation of key rate constants

Ascorbic acid is among the most abundant antioxidants in the lung, where it likely plays a key role in the mechanism by which particulate air pollution initiates a biological response. Because ascorbic acid is a highly redox active species, it engages in a far more complex web of reactions than a typical organic molecule, reacting with oxidants such as the hydroxyl radical as well as redox-active transition metals such as iron and copper. The literature provides a solid outline for this chemistry, but there are large disagreements about mechanisms, stoichiometries and reaction rates, particularly for the transition metal reactions. Here we synthesize the literature, develop a chemical kinetics model, and use seven sets of laboratory measurements to constrain mechanisms for the iron and copper reactions and derive key rate constants. We find that micromolar concentrations of iron(III) and copper(II) are more important sinks for ascorbic acid (both AH2 and AH−) than reactive oxygen species. The iron and copper reactions are catalytic rather than redox reactions, and have unit stoichiometries: Fe(III)/Cu(II) + AH2/AH− + O2 → Fe(III)/Cu(II) + H2O2 + products. Rate constants are 5.7 × 104 and 4.7 × 104 M−2 s−1 for Fe(III) + AH2/AH− and 7.7 × 104 and 2.8 × 106 M−2 s−1 for Cu(II) + AH2/AH−, respectively.

Gelation and vibrational spectroscopy of tropical surimi induced by ascorbic acid and hydrogen peroxide.

The combined effect of ascorbic acid (AsA) and hydrogen peroxide (H2 O2 ) on gel-forming ability and structural changes of lizardfish (LZ) and threadfin bream (TB) surimi were investigated. Addition of 0.15% AsA and 0.1% H2 O2 greatly increased breaking force and distance of LZ surimi by 300% and 55%, respectively. Combination of 0.2% AsA and 0.15% H2 O2 resulted in the maximum TB surimi gel improvement with 150% and 90% increase in breaking force and distance, respectively. Browning reaction obviously occurred when combined AsA and H2 O2 was added, due to ascorbic acid oxidation. Polymerization of myosin heavy chain via disulfide bonds was promoted, and the formation of disulfide bonds was involved through oxidation of sulfhydryl groups with increasing AsA and H2 O2 . Fourier-transform infrared (FT-IR) spectroscopy revealed a decrease in α-helix and an increase in β-sheet content as AsA and H2 O2 increased in both species. A decrease of band area of aliphatic (2,800 to 3,000 and 1,450 cm-1 ), aromatic (1,208, 757, and ratio 850/830 cm-1 ), and change of disulfide bonds (525 and 540 cm-1 ) suggested an increase in hydrophobic interactions and disulfide bonds with addition of these additives. Based on principal component analysis (PCA), textural characteristics were positively correlated with β-sheet content. Our study suggested that combination of AsA and H2 O2 greatly enhanced gelation of LZ and TB by increasing not only disulfide bonds but also hydrophobic interactions. PRACTICAL APPLICATION: The combined ascorbic acid and hydrogen peroxide can be used to improve gelation of two important tropical surimi species, namely threadfin bream and lizardfish surimi, without requirement of setting. The optimum concentration of each additive varied with fish species.

Addressing the surface coverage of Au nano-agglomerates and the electrochemical properties of modified carbon paste electrodes: Experimental and theoretical studies on ascorbic acid oxidation

This article shows the formation of Au nano-agglomerates when increasing amounts of gold nanoparticles (AuNP) are incorporated into carbon paste electrodes. The surface coverage by this agglomerates is related to the electro-oxidation of a widely studied redox compound, ascorbic acid (AA); by analyzing the effect on the oxidation peak potential (Ep,a) and oxidation peak current (ip,a). The effects of pH and scan rate on the Ep,a and ip,a were investigated by cyclic voltammetry, and enabled to estimate the transfer coefficient and the number of electrons involved in the rate determining step (αnα), the standard heterogeneous rate constant (ks), and the diffusion coefficient of the redox compound, being 0.52 and 3.5 × 10−3 cm s−1 and 6.3 × 10−6 cm2 s−1, respectively. On the other hand, the sensing ability of the modified electrode was evaluated, obtaining a sensitivity of (63.2 ± 2.5) μA mM−1, a detection limit of 2.7 μM and a quantification limit of 8.9 μM.Additionally, a computational model based on lattice-gas model and Monte Carlo simulations in the Grand Canonical Ensemble was proposed in order to reproduce the behavior of the system, in terms of ip,a and Ep,a shift with increasing surface coverage by Au nano-agglomerates.

A Cu-bis(imidazole) Substrate Intermediate Is the Catalytically Competent Center for Catechol Oxidase Activity of Copper Amyloid-β.

Interaction of copper ions with Aβ peptides alters the redox activity of the metal ion and can be associated with neurodegeneration. Many studies deal with the characterization of the copper binding mode responsible for the reactivity. Oxidation experiments of dopamine and related catechols by copper(II) complexes with the N-terminal amyloid-β peptides Aβ16 and Aβ9, and the Aβ16[H6A] and Aβ16[H13A] mutant forms, both in their free amine and N-acetylated forms show that efficient reactivity requires the oxygenation of a CuI-bis(imidazole) complex with a bound substrate. Therefore, the active intermediate for catechol oxidation differs from the proposed “in-between state” for the catalytic oxidation of ascorbate. During the catechol oxidation process, hydrogen peroxide and superoxide anion are formed but give only a minor contribution to the reaction.

Ascorbate Tumor Chemotherapy by An Iron-Engineered Nanomedicine-Catalyzed Tumor-Specific Pro-Oxidation.

Ascorbate, a kind of polyhydroxy compound with a long history, has been extensively considered as an efficient antioxidant. However, only in the past several decades its pro-oxidation characteristic in the presence of transition metal catalysts has been gradually uncovered, attracting broad attention from researchers in chemistry and biology for benefiting various practical applications, such as anticancer therapy. In this work, we report catalytic ascorbate oxidation and reactive oxygen species generation for efficient tumor chemotherapy by an iron-engineered and ascorbate-loaded hollow mesoporous silica nanomedicine. The -Si-O-Fe- hybrid framework of nanomedicine not only enables acidity-triggered degradability and ascorbate release capability but also provides an abundant Fe ion source for catalyzing ascorbate oxidation, hydrogen peroxide formation, and subsequent Fenton reactions. The detailed chemical mechanism of Fe3+-catalyzed ascorbate oxidation has been explored in detail as two one-electron reaction processes, between which the first one involves the sequential Fe3+ and O2 captures by ascorbate to form a metal-ascorbate-oxygen ternary complex favoring hydrogen peroxide generation. Both in vitro and in vivo results demonstrate the significantly enhanced anticancer efficacy of ascorbate oxidation catalyzed by the composite nanomedicine, demonstrating high feasibility of this synergistic therapeutic concept. It is expected that such a nanomedicine design would be beneficial to future advances in the field of ascorbate.

Electrochemical synthesis of 3D microstructured composite films of poly(3,4-ethylenedioxythiophene) and reduced nanographene oxide

Microstructured composite films based on poly(3,4-ethylenedioxythiophene) (PEDOT) and nanographene oxide (nGO) were prepared by electrochemical polymerization of 3,4-ethylenedioxythiophene in nGO aqueous solution on the surface of glassy carbon electrodes at a constant potential. The microstructure pattern of the electropolymerized films was shaped using microsphere lithography process with mono- or bilayers of polystyrene microspheres arranged on the electrode surface. During the electropolymerization, the nGO was incorporated into the composite film as a charge-compensating anion for PEDOT accelerating the electropolymerization process. We demonstrate that addition of small amount of sodium dodecyl sulfate to the reaction medium suppresses the aggregation of the nGO sheets resulting in a better defined defect-free morphology of the PEDOT:nGO films. After dissolving the template polystyrene particles, PEDOT:nGO films retained a porous honeycomb-like structure. The nGO incorporated into PEDOT:nGO composite was electrochemically converted to reduced nGO (nRGO) in a simple one-step reduction process. We show in this paper that the resulting PEDOT:nRGO films demonstrate increased redox capacitance and enhanced electroactivity for ascorbic acid oxidation.

Magnetic resonance imaging (MRI) of pharmacological ascorbate-induced iron redox state as a biomarker in subjects undergoing radio-chemotherapy

Pharmacological ascorbate (P-AscH-) combined with standard of care (SOC) radiation and temozolomide is being evaluated in a phase 2 clinical trial (NCT02344355) in the treatment of glioblastoma (GBM). Previously published data demonstrated that paramagnetic iron (Fe3+) catalyzes ascorbate's oxidation to form diamagnetic iron (Fe2+). Because paramagnetic Fe3+ may influence relaxation times observed in MR imaging, quantitative MR imaging of P-AscH--induced changes in redox-active Fe was assessed as a biomarker for therapy response.Gel phantoms containing either Fe3+ or Fe2+ were imaged with T2* and quantitative susceptibility mapping (QSM). Fifteen subjects receiving P-AscH- plus SOC underwent T2* and QSM imaging four weeks into treatment. Subjects were scanned: pre-P-AscH- infusion, post-P-AscH- infusion, and post-radiation (3–4 h between scans). Changes in T2* and QSM relaxation times in tumor and normal tissue were calculated and compared to changes in Fe3+ and Fe2+ gel phantoms. A GBM mouse model was used to study the relationship between the imaging findings and the labile iron pool.Phantoms containing Fe3+ demonstrated detectable changes in T2* and QSM relaxation times relative to Fe2+ phantoms. Compared to pre-P-AscH-, GBM T2* and QSM imaging were significantly changed post-P-AscH- infusion consistent with conversion of Fe3+ to Fe2+. No significant changes in T2* or QSM were observed in normal brain tissue. There was moderate concordance between T2* and QSM changes in both progression free survival and overall survival. The GBM mouse model showed similar results with P-AscH- inducing greater changes in tumor labile iron pools compared to the normal tissue. ConclusionsT2* and QSM MR-imaging responses are consistent with P-AscH- reducing Fe3+ to Fe2+, selectively in GBM tumor volumes and represent a potential biomarker of response. This study is the first application using MR imaging in humans to measure P-AscH--induced changes in redox-active iron.

Impact of processing and storage conditions on color stability of strawberry puree: The role of PPO reactions revisited

The effect of pre-heating fresh strawberries (hot break) and the use of refrigerated temperatures prior to pasteurization on the stability of anthocyanins, vitamin C, color and polyphenol oxidase (PPO) activity during storage (42 days at 35 °C) of strawberry puree was studied. Hot break resulted in 20% residual PPO activity and caused 10% anthocyanin degradation, whereas vitamin C was unaffected. After mashing, purees were stored at 4 °C and 25 °C for 3 h. During this period, anthocyanins and PPO activity remained constant independently of the processing history but ascorbic acid was oxidized faster at 25 °C. Pasteurization caused complete inactivation of PPO, reduction of anthocyanins (25%), of a* value (6%) and of vitamin C (50%). Neither partial inactivation of PPO early in the processing (hot break) nor the use of refrigeration prior to pasteurization had a positive effect on color and anthocyanin stability of strawberry puree during subsequent storage, suggesting that PPO-derived reaction products formed during processing have a very limited impact on color degradation during shelf-life. • Different strawberry puree manufacturing processing conditions were evaluated. • Hot break did not improve color stability during further processing and storage. • Refrigeration prior to pasteurization prevented ascorbic acid oxidation. • PPO reactions before pasteurization do not affect color degradation during storage. • “Impact of processing and storage conditions on color stability of strawberry puree: the role of PPO reactions revisited”.

Intermediates of the Photoinduced 2,4-Bis(4-diethylaminobenzylidene)cyclobutanone Redox Reaction in Methanol

Formation of intermediates (triplet states, radical anions, and radical cations) has been revealed by pulse laser photolysis in the photoinduced redox reaction of 2,4-bis(4-diethylaminpbenzyliden)cyclobutanone in methanol in the presence of an electron donor (ascorbic acid) and electron acceptors (methylviologen and p-nitroacetophenone). The reactions of photoinduced reduction by ascorbic acid and oxidation by methylviologen and p-nitroacetophenone occur via the triplet state with the formation of the dye radical anion and radical cation, respectively. The formation of the radical products of the photoinduced redox reaction is characterized by short-lived changes in the absorption spectra at λmax = 460 nm and a lifetime of 3 × 10−4 s for the radical anion and at λmax = 395 and 620 nm and a lifetime of 5 × 10−5 s for the radical cation.

Oxidation of L-Ascorbic Acid in the Presence of the Copper-Binding Compound from Methanotrophic Bacteria Methylococcus capsulatus (M).

The oxidation of ascorbic acid by air oxygen and hydrogen peroxide in the presence of the copper-binding compound (cbc) from bacteria Methylococcus capsulatus (M) was studied. The rate constant of ascorbic acid oxidation by air oxygen in the presence of the copper complex with cbc from M. capsulatus (M) was shown to be 1.5 times higher than that of the noncatalytic reaction. The rate constant of ascorbic acid oxidation by hydrogen peroxide in the presence of the copper complex with cbc from M. capsulatus (M) decreased by almost one-third compared to the reaction in the absence of the copper complex with cbc. It was assumed that cbc can be involved in a multilevel system of antioxidant protection and can protect a bacterial cell from oxidation stress. Thus, the cbc is mimetic ascorbate oxidase in the oxidation of ascorbic acid by molecular oxygen.

Solvent-dependent self-assembly of a ruthenium(II) complex bearing triazino-phenanthrenes and its applications in photocatalytic ascorbate fuel cells

The triazine-based metal-organic frameworks (MOFs) are of great significance in a photocatalytic or electrocatalytic system. This paper reports solvent-dependent self-assembly and photoelectrochemical properties of [Ru(ptp)2]2+ (ptp = 3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6,f]phenanthrene) and its photoelectrocatalysis to ascorbate (AA) oxidation and oxygen reduction in photocatalytic fuel cells. [Ru(ptp)2]2+ can be dissolved in ethanol (E), ethanol/water mixtures (M), or water (W) to produce three forms of aggregates, which are further assembled into [Ru(ptp)2]2+ modified CdS photoanodes. The MOF form of [Ru(ptp)2]2+-M shows the maximum absorbance at ethanol/water of 1:1 (Ve/Vw), and the resulting [Ru(ptp)2]2+-M/CdS electrode has better conductivity, larger light-harvesting efficiency and photovoltaic response compared with that of [Ru(ptp)2]2+-E/CdS. Furthermore, [Ru(ptp)2]2+-M exhibits enhanced photoelectrocatalytic activity towards ascorbate oxidation and oxygen reduction. The simultaneous presence of [Ru(ptp)2]2+-M on CdS photoanode and single-walled carbon nanotubes (SWCNTs) cathode used in visible light-excited ascorbate fuel cells, leads to a 1.1-fold or 4.5-fold increase in the open-circuit voltage or maximum power density. This present study provides a significant platform for solvent-dependent self-assembly of triazino-phenanthrene-containing metal complexes and improvement of photocatalytic fuel cell performances.

Ascorbate oxidation activates systemic defence against root-knot nematode Meloidogyne graminicola in rice.

Ascorbic acid (AA) is the major antioxidant buffer produced in the shoot tissue of plants. Previous studies on root-knot nematode (RKN; Meloidogyne graminicola)-infected rice (Oryza sativa) plants showed differential expression of AA-recycling genes, although their functional role was unknown. Our results confirmed increased dehydroascorbate (DHA) levels in nematode-induced root galls, while AA mutants were significantly more susceptible to nematode infection. External applications of ascorbate oxidase (AO), DHA, or reduced AA, revealed systemic effects of ascorbate oxidation on rice defence versus RKN, associated with a primed accumulation of H2O2 upon nematode infection. To confirm and further investigate these systemic effects, a transcriptome analysis was done on roots of foliar AO-treated plants, revealing activation of the ethylene (ET) response and jasmonic acid (JA) biosynthesis pathways in roots, which was confirmed by hormone measurements. Activation of these pathways by methyl-JA, or ethephon treatment can complement the susceptibility phenotype of the rice Vitamin C (vtc1) mutant. Experiments on the jasmonate signalling (jar1) mutant or using chemical JA/ET inhibitors confirm that the effects of ascorbate oxidation are dependent on both the JA and ET pathways. Collectively, our data reveal a novel pathway in which ascorbate oxidation induces systemic defence against RKNs.

Effects of fullerene C60 supplementation on gut microbiota and glucose and lipid homeostasis in rats

The effects of twelve weeks of supplementation with fullerene C60 olive/coconut oil solution on a broad spectrum of parameters in rats were examined. The tissue bioaccumulation of C60 was shown to be tissue-specific, with the liver, heart, and adrenal glands being the organs of the greatest, and the kidney, brain, and spleen being the organs of the smallest accumulation. C60 did not change aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase serum activities level, nor the damage of liver cells DNA. There were no effects of fullerene on prooxidant-antioxidant balance in the liver, kidney, spleen, heart, and brain, nor any visible harmful effects on the liver, heart, aorta, spleen, kidney, and small intestine histology. Fullerene changed the gut microbiota structure towards the bacteria that ameliorate lipid homeostasis, causing a serum triglycerides concentration decrease. However, C60 significantly increased the insulin resistance, serum ascorbate oxidation, and brain malondialdehyde and advanced oxidation protein products level. The deteriorative effects of C60 on the brain and serum could be attributed to the specific physicochemical composition of these tissues, potentiating the C60 aggregation or biotransformation as the key element of its pro-oxidative action.

The Glutathione/Metallothionein System Challenges the Design of Efficient O2 -Activating Copper Complexes.

Copper complexes are of medicinal and biological interest, including as anticancer drugs designed to cleave intracellular biomolecules by O2 activation. To exhibit such activity, the copper complex must be redox active and resistant to dissociation. Metallothioneins (MTs) and glutathione (GSH) are abundant in the cytosol and nucleus. Because they are thiol-rich reducing molecules with high CuI affinity, they are potential competitors for a copper ion bound in a copper drug. Herein, we report the investigation of a panel of CuI /CuII complexes often used as drugs, with diverse coordination chemistries and redox potentials. We evaluated their catalytic activity in ascorbate oxidation based on redox cycling between CuI and CuII , as well as their resistance to dissociation or inactivation under cytosolically relevant concentrations of GSH and MT. O2 -activating CuI /CuII complexes for cytosolic/nuclear targets are generally not stable against the GSH/MT system, which creates a challenge for their future design.