Ferricyanide Research Articles

Quantificação de compostos fenólicos, poder antioxidante e teor de açúcares em produtos comerciais a base de Camellia sinensis L.

Objetivo: Analisar e comparar quantitativamente compostos fenólicos, capacidade antioxidante e açúcares presentes em infusões e extratos solúveis de Camellia sinensis L. Metodologia: O estudo apresenta delineamento inteiramente casualizado, utilizando amostras por conveniência. Foram adquiridas três amostras aleatórias de cada tipo de chá. As análises de compostos fenólicos totais e flavonoides foram determinadas pelo método colorimétrico de Folin-Ciocalteu e cloreto de alumínio, respectivamente, taninos totais por complexação com caseína e os condensados pelo método do butanol-HCl. A capacidade antioxidante, pela metodologia do ferricianeto e sequestro de radicais livres pelo radical 2,2-difenil-1-picril-hidrazil, e os açúcares redutores e não redutores, através do reagente ácido 3-5-dinitrossalicílico. Resultado: Os extratos infusos apresentaram quantidades significativamente maiores de compostos fenólicos totais e flavonoides em comparação ao solúvel. Esse comportamento foi o mesmo para os taninos e atividade antioxidante. As infusões obtiveram maior poder redutor e capacidade de redução do radical livre. Os extratos solúveis foram destaque, com maior presença de açúcares. Esses resultados foram confirmados pela literatura e não houve trabalhos realizados com extratos solúveis e metodologias semelhantes ao realizado aqui para comparação. Conclusão: As infusões estudadas no presente trabalho foram mais ricas em compostos bioativos e antioxidantes, favorecendo seus benefícios para a população, tendo os extratos solúveis maior presença de açúcares adicionais.

Effect of Poly-l-Lysine Polycation on the Glucose Oxidase/Ferricyanide Composite-Based Second-Generation Blood Glucose Sensors.

Second-generation glucose biosensors are presently the mainstream commercial solution for blood glucose measurement of diabetic patients. Screen-printed carbon electrodes (SPCEs) are the most-used substrate for glucose testing strips. This study adopted hydrophilic and positively charged α-poly-l-lysine (αPLL) as the entrapment matrix for the immobilization of negatively charged glucose oxidase (GOx) and ferricyanide (FIC) on SPCEs to construct a disposable second-generation glucose biosensor. The αPLL modification is shown to facilitate the redox kinetics of FIC and ferrocyanide on the SPCEs. The SPCEs coated with 0.5 mM GOx, 99.5 mM FIC, and 5 mM αPLL had better sensitivity for glucose detection due to the appreciable effect of protonated αPLL on the promotion of electron transfer between GOx and FIC. Moreover, the SPCEs coated with 0.5 mM GOx, 99.5 mM FIC, and 5 mM αPLL were packaged as blood glucose testing strips for the measurement of glucose-containing human serum samples. The glucose testing strips had good linearity from 2.8 mM to 27.5 mM and a detection limit of 2.3 mM. Moreover, the 5 mM αPLL-based glucose testing strips had good long-term stability to maintain GOx activity in aging tests at 50 °C.

Measuring Trans-Plasma Membrane Electron Transport by C2C12 Myotubes.

Trans-plasma membrane electron transport (tPMET) plays a role in protection of cells from intracellular reductive stress as well as protection from damage by extracellular oxidants. This process of transporting electrons from intracellular reductants to extracellular oxidants is not well defined. Here we present spectrophotometric assays by C2C12 myotubes to monitor tPMET utilizing the extracellular electron acceptors: water-soluble tetrazolium salt-1 (WST-1) and 2,6-dichlorophenolindophenol (DPIP or DCIP). Through reduction of these electron acceptors, we are able to monitor this process in a real-time analysis. With the addition of enzymes such as ascorbate oxidase (AO) and superoxide dismutase (SOD) to the assays, we can determine which portion of tPMET is due to ascorbate export or superoxide production, respectively. While WST-1 was shown to produce stable results with low background, DPIP was able to be re-oxidized after the addition of AO and SOD, which was demonstrated with spectrophotometric analysis. This method demonstrates a real-time, multi-well, quick spectrophotometric assay with advantages over other methods used to monitor tPMET, such as ferricyanide (FeCN) and ferricytochrome c reduction.

اثر حلالهای مختلف و امواج فراصوت بر خاصیت آنتیاکسیدانی عصاره میوه زغال اخته

میوه زغال اخته به دلیل داشتن ترکیبات ارزشمند فراوانی مانند ترکیبات فنولی، منبع خوبی از آنتی‌اکسیدان‌های طبیعی است و می‌تواند به‌عنوان گیاه دارویی در درمان بسیاری از بیماری‌ها مورد استفاده قرار گیرد. در این مطالعه، تاثیر روش‌های استخراج (غرقابی و اولتراسوند) و حلال (اتانول100%، آب- اتانول به نسبت 50:50 حجمی-حجمی و آب) بر میزان ترکیبات فنولی استخراجی و خواص آنتی‌اکسیدانی عصاره میوه زغال اخته مورد بررسی قرار گرفت. محتوای فنول کل عصاره‌ها با روش فولین سیوکالتیو تعیین شد. فعالیت آنتی‌اکسیدانی عصاره‌ها با استفاده از سنجش قدرت احیاکنندگی آهن III و مهار رادیکال‌های آزاد DPPH مورد بررسی قرار گرفت. نتایج این پژوهش نشان داد که نوع حلال و روش استخراج بر مقدار ترکیبات فنولی عصاره‌ها تاثیر گذار بوده است و همچنین وابستگی غلظت ترکیبات فنولی با خاصیت آنتی‌اکسیدانی در همه عصاره‌ها مشاهده شد. بالاترین مقدار ترکیبات فنولی با 72/142 میلی‌گرم بر گرم (برحسب اسید گالیک) متعلق به عصاره میوه زغال اخته حاصل از حلال آب- اتانول ( 50:50 حجمی/ حجمی) به کمک روش اولتراسوند بوده است. هم چنین این عصاره با کمترین IC50 با مقدار 955/0 میلی‌گرم بر میلی‌لیتر در روش مهار رادیکال‌های آزاد DPPHو بالاترین جذب با مقدار 601/0 در آزمون قدرت احیاکنندگی آهن III، بالاترین کارایی آنتی‌اکسیدانی را نشان داده است.

Multiwalled Carbon Nanotubes Based Immunosensor for Diagnosis ofCeliac Disease

Celiac Disease (CD) is an autoimmune disorder, represented by the ingestion of gliadin protein usually found in wheat, barley and rye. CD is closely associated with genes that code HLA-II antigens, mainly of DQ2 and DQ8 classes. Small intestinal biopsy is considered the gold standard for diagnosis of celiac disease. In addition, the most sensitive tests for the diagnosis of celiac disease include the increase in level of IgA isotype of anti-gliadin antibodies, connective tissue antibodies and tissue transglutaminase antibodies. In the present study, an amperometric immunosensor was fabricated for CD diagnosis using multiwalled carbon nanotubes screen printed electrode. Antigen (gliadin) was covalently linked to carbon nanotubes through 1-Ethyl-3-(3-dimethylaminopropyl carbodiimide) (EDC)- N-hydroxysuccinimide (NHS) cross linking chemistry. Different concentrations of anti-gliadin antibodies were added on working electrode surface and change in current was measured by Cyclic Voltammetry using redox indicator Potassium ferricyanide [K3Fe(CN)6]. Electrochemical studies showed that the immunosensor was able to detect the antibody concentration as low as 0.13ng/μl. Sensitivity of the immunosensor was found to be 119.2 (μA/cm2)/ng. The present sensor can be used for diagnosis of celiac patients who are sensitive to gluten ingestion.

Buoyancy Effect of Ionic Vacancy on the Change of the Partial Molar Volume in Ferricyanide-Ferrocyanide Redox Reaction under a Vertical Gravity Field

With a gravity electrode (GE) in a vertical gravity field, the buoyancy effect of ionic vacancy on the change of the partial molar volume in the redox reaction between ferricyanide (FERRI) and ferrocyanide (FERRO) ions was examined. The buoyancy force of ionic vacancy takes a positive or negative value, depending on whether the rate-determining step is the production or extinction of the vacancy. Though the upward convection over an upward electrode in the FERRO ion oxidation suggests the contribution of the positive buoyancy force arising from the vacancy production, the partial molar volume of the vacancy was not measured. On the other hand, for the downward convection under a downward electrode in the FERRI ion reduction, it was not completely but partly measured by the contribution of the negative buoyancy force from the vacancy extinction. Since the lifetime of the vacancy is decreased by the collision between ionic vacancies during the convection, the former result was ascribed to the shortened lifetime due to the increasing collision efficiency in the enhanced upward convection over an upward electrode, whereas the latter was thought to arise from the elongated lifetime due to the decreasing collision efficiency by the stagnation under the downward electrode.

Two-dimensional fluorescence difference gel electrophoresis analysis of Listeria monocytogenes submitted to a redox shock

The influence of redox alteration on the growth and proteomic pattern of Listeria monocytogenes was investigated. A redox shock was induced in cultures by addition of 3mM ferricyanide (FeCN) and 6mM dithiothreitol (DTT) to increase or to decrease respectively the redox potential naturally occurring at the beginning of growth. In both conditions, the reducing and oxidizing redox shock had a strong influence, decreasing the maximum growth rate by half compared to a control culture. The proteomic analysis of L. monocytogenes performed by two-dimensional difference gel electrophoresis (2D-DIGE) exhibited twenty-three proteins differentially expressed (P<0.05), among these, many were oxidoreductases, and proteins involved in cellular metabolism (glycolysis, protein synthesis), detoxification (kat) or adhesion (Lmo1634).

Measurement of the change in partial molar volume during electrode reaction by gravity electrode—II. Examination of the accuracy of the measurement

The reliability of the measurement of the change in partial molar volume between product and reactant ions measured by gravity electrode (GE) was examined by the thermodynamic measurement of pycnometer (PM). Since the PM method requires an experimental equation of the apparent molar volume to calculate the partial molar volumes of the individual ions, the most suitable experimental equation must be first determined. As a test reaction for the experiment, oxidation of ferrocyanide (FERO) ion to ferricyanide (FERI) ion was adopted. After fitting several experimental equations to the data of the apparent molar volumes by the PM method, the calculated changes in the partial molar volume were compared with the data of the GM method. Then, it is concluded that the polynomial with a degree of 3 of the logarithm of the molality of the FERO ion suggests the most suitable equation. As a result, the reliability of the GE method was also experimentally validated.

Portable cholesterol detection with polyaniline-carbon nanotube film based interdigitated electrodes

Polyaniline-carboxylic multiwalled carbon nanotubes composite film (PANi-MWCNT) has been polymerized on the surface of interdigitated platinum electrode (fabricated by MEMS technology) which was compatibly connected to Autolab interface via universal serial bus (USB). An amperometric biosensor based on covalent immobilization of cholesterol oxidase (ChOx) on PANi–MWCNT film with potassium ferricyanide (FeCN) as the redox mediator was developed. The mediator helps to shuttle the electrons between the immobilized ChOx and the PANi-MWCNT electrode, therefore operating at a low potential of −0.3 V compared to the saturated calomel electrode (SCE). This potential precludes the interfering compounds from oxidization. The bio-electrode exhibits good linearity from 0.02 to 1.2 mM cholesterol concentration with a correlation coefficient of 0.9985.

Spectrophotometric Determination of Cefotaxime Sodium with Potassium Ferricyanide

A spectrophotometric method has been set up to determine cefotaxime sodium using potassium ferricyanide as the spectroscopic probe reagent.With the presence of potassium ferricyanide,the degradation product of cefotaxime sodium can reduce Fe3 + to Fe2 + at pH 3.0,which facilitate the formation of soluble Prussian Blue(KFeⅢ[FeⅡ(CN) 6]).The absorbance of soluble Prussian Blue is measured at its absorption maximum of 730 nm and the amount of cefotaxime sodium can be indirectly calculated.Under optimized conditions,a good linear relationship is obtained in the range of 0.040 ～ 24 mg/L of cefotaxime sodium.The linear regression equation is A = 0.05088 + 0.2166ρ(mg/L) with linear correlation coefficient of 0.9986.The detection limit and relative standard deviation are 0.01 mg/L and 1.36%,respectively.Tthe apparent molar absorption coefficient of indirect determination of cefotaxime sodium is 2.3 × 105 L/(mol·cm).This method has been successfully applied to the determination of cefotaxime sodium in pharmaceutical and serum samples.

Mechanism of the Osmium(Viii)-Catalysed Oxidation of Fursemide by Alkaline Hexacyanoferrate(Iii) and Analysis of Fursemide by a Kinetic and Catalytic Method

The kinetics of the title reaction showed first-order behaviour both in hexacyanoferrate(III) and osmium(VIII) and fractional order each in fursemide and alkali concentrations. The added product, [Fe(CN)6]4-, retarded the rate of reaction. The active species of osmium(VIII) in alkali appears to be [OsO5(OH)]3-. A mechanism involving a complex formed between osmium(VIII) and fursemide, followed by its oxidation with hexacyanoferrate(III) in a rate-determining step is proposed. A rate law for the mechanism was derived and verified. The formation constant, K2 for [OsO5(OH)]3-, K3 for the complex, and the rate constant of the slow step, k, were evaluated. The activation parameters Ea, Δ H#, Δ S#, Δ G# and log A were calculated as 55.2 ± 2kJ mol−1, 52.7 ± 2 kJ mol−1, - 52.0 ± 2 JK−1 mol−1, 69.8 ± 2.5 kJ mol−1 and 6.5 ± 0.1 respectively. Fursemide is used in the pharmacotherapy for various diseases and it is also considered as a doping agent in sports. A simple and specific procedure for its analysis was developed being based on its oxidation by alkaline hexacyanoferrate(III) in the presence of trace amount of osmium(VIII) catalyst. Three different methods have been recommended, namely, the rate constant method, fixed time method and fixed change in optical density method. of these, the latter two were found to be fast, simple, and accurate. from these methods, fursemide could be analysed from a few micrograms to milligrams per cm3. The interference by binders of tablets, and other possible substances like proteins and amino acids, have also been studied.

ChemInform Abstract: Synthesis of Some Novel Benzobisthiazoles

Abstractvia reaction of o‐methoxythiobenzanilides with AIBN or basic ferricyanide

Conductivity of AOT/Triton X-100 Mixed Reverse Micelles

采用聚乙二醇辛基苯基醚（TritonX-100）和二（2-乙基己基）琥珀酸磺酸钠（AOT）双表面活性剂,与正己烷、正己醇和水构成混合反胶束体系;研究了表面活性剂质量比、助表面活性剂含量、水油体积比和温度等因素对反胶束体系导电性能的影响,同时采用循环伏安法研究了K3Fe（CN）6/K4Fe（CN）6在该体系中的电化学行为.结果表明：由两种表面活性剂构成的反胶束体系电导率σ明显大于单一表面活性剂反胶束体系电导率;体系电导率随AOT与TritonX-100的质量比w（w=mAOT∶mTritonX-100）的变化而变化,w为0-0.4时,电导率随w增大而线性增大,之后增加趋势变缓;w=0.96时,σ达到稳定值576μS·cm-1.混合体系电导率随溶水量的增大及温度的上升而提高;而增加助表面活性剂可显著降低体系的电导率.在所研究体系中,Fe（CN）36-/Fe（CN）46-电化学反应对的氧化还原峰电位几乎不随扫描速率变化,峰电位差约为75mV,峰电流的比值约为1,氧化峰电流与扫描速率的平方根成正比,说明K3Fe（CN）6/K4Fe（CN）6在混合反胶束体系中显示出良好的氧化还原可逆性,反应由扩散步骤控制.

Synthesis of Some Novel Benzobisthiazoles

The synthesis of angular and linear benzobisthiazoles via reaction of o-methoxythiobenzanilides with AIBN and basic ferricyanide is described.

Voltage-dependent blockade of delayed rectifier K+ current by nitroprusside and ferricyanide

NO donor nitroprusside (NP) is a biologically active drug with hypotensive and neurotropic properties. Its effects are due to NO as well as to other derivates, specifically ferricyanide (FC) and ferrocyanide (F(2+)C) ions. In the present work we studied effects of NP, FC, and F(2+)C on delayed rectifier K+ current. The experiments were conducted on isolated neurons of land snail Helix using two-microelectrode voltageclamp technique. Delayed rectifier K+ current often displayed abnormal rectification. NP (1 mM) caused voltage-dependent reduction of K+ current, which looked like enhancement of the abnormal rectification. FC (1 mM)—but not F(2+)C—acted likewise; the effects of NP and FC were not additive. Dibutiryl cGMP (dbcGMP) had an opposite effect, weakening abnormal rectification of the K+ current. Protein kinase inhibitor H-8 (10 μM) caused voltage-dependent reduction of the K+ current, as NP and FC did. The effects of H-8 and NP and effects of H-8 and FC were not additive. The results suggest that: (i) NP effects on delayed rectifier K+ current are mediated by FC and (ii) the effects of these drugs involve phosphorylation processes.

A novel approach based on ferricyanide-mediator immobilized in an ion-exchangeable biosensing film for the determination of biochemical oxygen demand

A novel biochemical oxygen demand (BOD) sensing method employing a ferricyanide (FC) mediator immobilized in an ion-exchangeable polysiloxane was developed. The ion-exchangeable polysiloxane containing alkylammonium groups (PAPS-Cl) was synthesized by sol–gel reaction of 3-(aminopropyl)trimethoxysilane (APTMOS) catalyzed by hydrochloric acid. FC was combined in PAPS-Cl via ion-association and the product was labeled as PAPS-FC, which was employed for a modified glassy carbon electrode. The apparent diffusion coefficient ( D app) of FC on the modified glassy carbon electrode was 9.8 × 10 −11 cm 2 s −1. In a three-electrode system, a linear relationship between the anodic current responses and glucose/glutamate (GGA) concentration was obtained up to 40 mg O 2 L −1 ( r = 0.994) when the reaction mixture was incubated for 30 min. Single sensor and piece-to-piece reproducibility were less than 3.8 and 7.7%, respectively. The effects of dissolved oxygen, pH, temperature and co-existing substances on the BOD responses were studied. The sensor responses to nine pure organic substances were compared with the conventional BOD 5 method and other biosensor methods. Detection results of seawater samples were compared with those obtained from the BOD 5 method and showed a good correlation ( r = 0.988).

Inhibition of glycerophosphate-dependent H 2O 2 generation in brown fat mitochondria by idebenone

The established protective effect of coenzyme Q (CoQ) analogs is dependent on the location of reactive oxygen species (ROS) generation. One of these analogs—idebenone (hydroxydecyl-ubiquinone) is used as an antioxidative therapeutic drug. We tested its scavenging effect on the glycerophosphate (GP)-dependent ROS production as this enzyme was shown as a new site in the mitochondrial respiratory chain where ROS can be generated. We observed that idebenone inhibits both GP- and succinate-dependent ROS production. Idebenone and CoQ 1 were found to be more efficient in the scavenging activity (IC 50: 0.052 and 0.075 μM, respectively) than CoQ 3 (IC 50: 45.8 μM). Idebenone also inhibited ferricyanide (FeCN)-activated, GP-dependent ROS production. Our data thus extend previous findings on the scavenging effect of idebenone and show that it can also eliminate GP-dependent ROS generation.

Electrochemical preparation and electrocatalytic properties of PEDOT/ferricyanide film-modified electrodes

The poly(3,4-ethylenedioxy thiophene) (PEDOT)/ferricyanide (FCN) film was synthesized by a potentiostatic and also using potentiodynamic methods namely cyclic voltammetric and chronoamperometric techniques. The EQCM technique was used to study the mechanism of the incorporation of ferricyanide ions on the PEDOT film. The UV–vis absorption results too confirmed the presence of ferricyanide with the PEDOT film. The electrocatalytic oxidation of ascorbic acid was carried out on a glassy carbon electrode modified with the PEDOT/FCN film through cyclic voltammetry, chronoamperometry and rotating disk electrode (RDE) voltammetry as diagnostic techniques. It was found that the catalytic current depended on the concentration of ascorbic acid. The number of electron transfer involved in the rate-determining step was found to be 1 and transfer coefficient ( α) equal to 0.476. The diffusion coefficient of ascorbic acid was also estimated through the chrono amperometric and rotating disk electrode methods. The D values of ascorbic acid obtained by through the cyclic and chronoamperometric methods were found to be 4.4103 × 10 −6 and 4.9595 × 10 −6 cm 2 s −1, respectively. This modified electrode was also used for the simultaneous determination of ascorbic acid and dopamine.

CNS neurons express two distinct plasma membrane electron transport systems implicated in neuronal viability.

Trans-plasma membrane electron transport is critical for maintaining cellular redox balance and viability, yet few, if any, investigations have studied it in intact primary neurons. In this investigation, extracellular reduction of 2,6-dichloroindophenol (DCIP) and ferricyanide (FeCN) were measured as indicators of trans-plasma membrane electron transport by chick forebrain neurons. Neurons readily reduced DCIP, but not FeCN unless CoQ(1), an exogenous ubiquinone analog, was added to the assays. CoQ(1) stimulated FeCN reduction in a dose-dependent manner but had no effect on DCIP reduction. Reduction of both substrates was totally inhibited by epsilon-maleimidocaproic acid (MCA), a membrane-impermeant thiol reagent, and slightly inhibited by superoxide dismutase. Diphenylene iodonium, a flavoenzyme inhibitor, completely inhibited FeCN reduction but had no affect on DCIP reduction, suggesting that these substrates are reduced by distinct redox pathways. The relationship between plasma membrane electron transport and neuronal viability was tested using the inhibitors MCA and capsaicin. MCA caused a dose-dependent decline in neuronal viability that closely paralleled its inhibition of both reductase activities. Similarly capsaicin, a NADH oxidase inhibitor, induced a rapid decline in neuronal viability. These results suggest that trans-plasma membrane electron transport helps maintain a stable redox environment required for neuronal viability.

Charge transfer across the water/nitrobenzene interface by three-electrode system

A droplet of aqueous solution containing a certain molar ratio of redox couple is first attached onto a platinum electrode surface, then the resulting drop electrode is immersed into the organic solution containing very hydrophobic electrolyte. Combined with reference and counter electrodes, a classical three-electrode system has been constructed. Ion transfer (IT) and electron transfer (ET) are investigated systematically using three-electrode voltammetry. Potassium ion transfer and electron transfer between potassium ferricyanide in the aqueous phase and ferrocene in nitrobenzene are observed with potassium ferricyanide/potassium ferrocyanide as the redox couple. Meanwhile, the transfer reactions of lithium, sodium, potassium, proton and ammonium ions are obtained with ferric sulfate/ferrous sulfate as the redox couple. The formal transfer potentials and the standard Gibbs transfer energy of these ions are evaluated and consistent with the results obtained by a four-electrode system and other methods.