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Hydroxybenzoic acids are an important class of polyphenols because their strong antioxidative activity. In this study, the antioxidant activity of three hydroxybenzoic acids was investigated using the Briggs-Rauscher reaction. Besides individual gallic, protocatechuic, and vanillic acids at concentrations of 250, 500, and 1000 µM respectively, the various mixtures of two and three hydroxybenzoic acids were also tested. The highest antioxidant activity showed protocatechuic acid at a concentration of 1000 µM while the lowest antioxidant activity was observed for vanillic acid at a concentration of 250 µM. The most of investigated hydroxybenzoic acids mixtures showed some degree of antagonistic effect. The highest antagonistic effect was found for the equimolar mixture of protocatechuic and vanillic acid at concentration of 250 μM. On the contrary, the equimolar mixture of gallic acid and vanillic acid at the same concentration indicated a high synergistic effect. [ABSTRACT FROM AUTHOR]

Autocatalysis induces nonlinearity in chemical and/or biological systems, and is important for understanding the emergence of life in nature. To enhance the autonomy of self‐propulsion in an open system, we introduced a Briggs–Rauscher (BR) reaction into self‐propelled droplet systems. In this study, a droplet composed of a BR solution in an oil phase containing a monoolein surfactant exhibited various types of motion, that is, continuous, oscillatory, and no motions of the droplet. The motions observed depended on the concentrations of potassium iodate and hydrogen peroxide in the BR solution. These results indicated that the driving force in this system was generated by the reaction between monoolein and one of the intermediates of the BR reaction, iodine. Our system can contribute to the establishment of a novel biomimetic object in which the autocatalytic process acts as a key factor for inducing various types of motion. [ABSTRACT FROM AUTHOR]

Indigo carmine is a commonly used industrial blue dye. To determine its concentration in a commercially available food dye composed of a mixture of indigo carmine and D-glucose, this paper characterizes it through (ATR, KBr) FTIR micro-Raman as well as UV/Vis and clock: Briggs–Rauscher (BR) oscillatory reaction methods. The indigo carmine was detected in the bulk food dye only by applying micro-Raman spectroscopy, indicating a low percentage of the indigo carmine present. This research provides an improvement in the deviations from the experimental Raman spectrum as calculated by the B97D/cc-pVTZ level of theory one, resulting in a better geometrical optimization of the indigo carmine molecule compared to data within the literature. The analytical curves used to determine indigo carmine concentrations (and quantities) in an aqueous solution of food dye were applied by means of UV/Vis and BR methods. BR yielded significantly better analytical parameters: 100 times lower LOD and LOQ compared to commonly used UV/Vis. The remarkable sensitivity of the BR reaction towards indigo carmine suggests that not only does indigo carmine react in an oscillatory reaction but also its decomposition products, meaning that the multiple oxidation reactions have an important role in the BR's indigo carmine mechanism. The novelty of this research is the investigation of indigo carmine using a clock BR reaction, opening new possibilities to determine indigo carmine in other complex samples (pharmaceutical, food, etc.). [ABSTRACT FROM AUTHOR]

Experimental studies on BR system employing mixed organic substrates and Mn(II) as the catalyst are reported keeping Malonic acid as the common substrate whereas itaconic acid, citraconic acid (CsA) and mesaconic acid (MsA) act as the co-substrates. It may be noted that no oscillations were observed when the co-substrates were used alone and the addition of these to the main system provides different modes of oscillatory behavior such as entrainment, independent, partial inhibition or complete inhibition. The oscillatory parameters like induction period, time period and iodide ion concentration show a different trend while changing the concentrations of mixed organic substrates, potassium iodate, manganese (II) sulfate, hydrogen peroxide and sulfuric acid. The favorable reaction conditions and most appropriate reagent concentrations for optimal oscillatory behavior of the system under investigation are reported. The effect of organic substrates on Dushman reaction, which is one of the essential reaction steps in BR system, has been investigated using spectrophotometry and cyclic voltammetry. Further, the EPR studies indicate the important role of free radicals in influencing the reaction dynamics. Further, the rate of iodination reaction of the organic substrates is dependent on their structure/available reaction sites for iodination and as such this work proposes a new approach to distinguish between cis/trans (CsA/MsA) isomers using spectrophotometry. [ABSTRACT FROM AUTHOR]

The calcium phosphate tungsten bronze (Ca-PWB) has been synthesized and characterized (TGA, DSC, XRPD, FTIR, SEM). The influence of solid insoluble materials Ca- PWB, as well as lithium doped (Li-PWB) and cation free phosphate tungsten (PWB) bronzes on the oscillatory Briggs-Rauscher (BR) reaction dynamics, is compared. The results show that doping with Li and Ca reduces sensitivity of the BR reaction towards bronzes addition. These findings suggest the usage of the BR reaction as an innovative method for testing of different properties of bronze material. The behavior of PWB in the BR reaction is significantly changed with divalent cation (Ca2+) doping. The reasons for the different bronzes behavior were found in their calculated unit cell volumes. Namely, the compressed Ca-PWB unit cell volume indicates the difficult availability of the active site for heterogeneous catalysis. Hence, the linear correlation (slope) of the BR oscillogram’s length (τosc) vs. mass of bronze in BR reaction might be considered as a new parameter for the evaluation of the bronzes catalytic activity.

In this work, we describe the crazy-clock phenomenon involving the state I (low iodide and iodine concentration) to state II (high iodide and iodine concentration with new iodine phase) transition after a Briggs–Rauscher (BR) oscillatory process. While the BR crazy-clock phenomenon is known, this is the first time that crazy-clock behavior is linked and explained with the symmetry-breaking phenomenon, highlighting the entire process in a novel way. The presented phenomenon has been thoroughly investigated by running more than 60 experiments, and evaluated by using statistical cluster K-means analysis. The mixing rate, as well as the magnetic bar shape and dimensions, have a strong influence on the transition appearance. Although the transition for both mixing and no-mixing conditions are taking place completely randomly, by using statistical cluster analysis we obtain different numbers of clusters (showing the time-domains where the transition is more likely to occur). In the case of stirring, clusters are more compact and separated, revealed new hidden details regarding the chemical dynamics of nonlinear processes. The significance of the presented results is beyond oscillatory reaction kinetics since the described example belongs to the small class of chemical systems that shows intrinsic randomness in their response and it might be considered as a real example of a classical liquid random number generator.

Phenolic acids have been attracting huge attention over recent years due to their prominent antioxidant activity and potential health benefits. In this study, the antioxidant activity of caffeic, ferulic, and rosmarinic acids was evaluated using Briggs-Rauscher reaction method. In addition to single phenolic acids at different concentrations (50, 100, 200 and 250 μM), equimolar mixtures of two phenolic acids and all three phenolic acids were tested. The best ability to inhibit oscillations, i.e. the highest antioxidant activity showed rosmarinic acid at a concentration of 250 μM. Inhibition time of the Briggs-Rauscher oscillating reaction mixture was obtained experimentally for the different combinations of phenolic acids and compared with theoretical values calculated by adding up the effects of phenolic acids analyzed individually. The most of tested phenolic acids mixtures showed a difference in the antioxidant activity when compared to individual values of their constituents. The highest synergistic effect showed a mixture of caffeic acid and ferulic acid at a concentration of 250 μM while the highest antagonistic effect showed the mixture of caffeic acid, ferulic acid and rosmarinic acid at same concentration [ABSTRACT FROM AUTHOR]

Phosphate tungsten bronzes, obtained by thermal treatment, are insufficiently investigated bronzes and there is scarce literature data on their chemical behavior and structure. Due to high-sensitivity of the Briggs-Rauscher (BR) reaction to addition of different analytes, this oscillatory reaction presents a potentially important chemical system for investigation and characterization of phosphate-tungsten bronzes, doped and undoped. The reaction mixture for the oscillatory BR reaction typically consists of H2O2, HClO4, KIO3, Mn(II) (catalyst), and CH2(COOH)2 (malonic acid, as an organic substrate). This paper deals with phosphate tungsten bronzes (PWB) and lithium doped phosphate tungsten bronzes (LiPWB) and their effects on the Briggs-Rauscher reaction dynamics. It is shown that the addition of phosphate tungsten bronzes decreases the oscillatory period length in this reaction. Furthermore, the obtained results show that PWB has a stronger influence on the BR reaction dynamics then LiPWB. In both cases, the oscillatory period is a linear function of the added bronze mass. The obtained linear functions can be successfully used for determination of the unknown bronze mass. Furthermore, due to different slopes of these functions, the Briggs-Rauscher reaction can be used as a system-detector for lithium doped and undoped phosphate tungsten bronzes. In order to elucidate the mechanism of bronze action, the inductively coupled plasma optical emission spectrometry (ICP-OES) was used to measure the total contents of K, Mn, W, Li. The aliquots of the above solution (i.e. CH2(COOH)2, MnSO4, HClO4, KIO3 but without H2O2) with the identical masses of PWB and LiPWB were examined. For the sake of comparison, contents of the metals in the solution without the bronze addition were measured, as well. Results obtained by the ICP-OES analysis show that the bronze structure is disturbed in the strong oxidizing environment (iodate in acidic solution) so that both, tungsten and lithium, leach into the BR solution. Accordingly, the proposed mechanism of the bronze action is probably by the reaction of tungsten ion with hydrogen-peroxide resulting in formation of a tungsten-peroxo complex. This complex is a stronger oxidizing agent then hydrogen peroxide itself. Thus, formation of the tungsten-peroxo complex potentially affects the kinetics of the Briggs-Rauscher reaction. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172015, Grant no. III45001 and Grant no. III45014]

Superoxide radical is one of the main players when it comes to oxidative stress. Even if in itself is moderately reactive and can cause the degradation of very few biologically relevant macromolecules, it can dismutate to hydrogen peroxide followed by a possible conversion to hydroxyl radical. In order to protect the internal environment against reactive oxygen species, plants have evolved a line of defence made from secondary metabolites with versatile redox properties, such as flavonoids and phenolic acids. Their characteristics are highly modulated by pH, as they turn into prooxidant compounds as it increases. Reported here are the behaviour and clear patterns in reactivity towards superoxide anion radical of four classes of plant phenolics as a pH function. The reactivity towards superoxide radical in acidic conditions has been studied by use of oscillating Briggs-Rauscher reaction with a new spectroelectrochemical experimental setup, by recording the absorbance in high quality for the first time. Some mechanistic intricacies have also been explored with regard to this method. Reactivity modulation at neutral and slightly basic pH has been assayed by superoxide radical scavenging ability using nitroblue tetrazolium as a substrate. For stronger alkaline pHs studies, Electron Paramagnetic Resonance was exploited. Hydroxybenzoic acids tend to be the least reactive species at all tested pH values. Hydroxycinnamic acids have their activity towards superoxide radical decreased as the pH increases, whereas flavonoids act vice versa. Image 1 • Ten polyphenolics were characterised using inhibition of Briggs-Rauscher reaction. • Their ability to scavenge hydroperoxyl at low and neutral pH was evaluated. • In alkaline medium they exbibit prooxidant activity via superoxide generation. • At low pH, glycosylated polyphenolics display higher hydroperoxyl scavenging ability. • Hydroxybenzoic acid derivatives, are the weakest superoxide scavengers at any pH. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Works of the Faculty of Forestry University of Sarajevo is the property of Faculty of Forestry University of Sarajevo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Dushman reaction (reduction of iodate by iodide) is a subsystem of the Briggs-Rausher oscillating reaction. We show that the previously observed effects of Ce(III) and Mn(II) on the kinetics of the Dushman reaction are mainly ionic strength effects. The observed decrease of the rate constant of the Dushman reaction when the ionic strength increases and the formation of the ion pairs MnSO(aq) and CeSO explain quantitatively our kinetic results. We also show why the original mechanism of the Briggs-Rausher reaction must be revised and propose a variant of the mechanism proposed in 2002 by Furrow, Cervellati and Amadori. This variant establishes a relationship with the reduction of iodate by high concentrations of hydrogen peroxide and the non-catalyzed BR reaction. [ABSTRACT FROM AUTHOR]

The oscillatory behavior is not the only interesting nonlinear phenomena that appeared in the Briggs-Rauscher (BR) reaction. The BR reaction containing malonic acid may undergo a sudden transition from low (the state I) to high iodide and iodine (the state II) concentration states. This paper focuses on the mixture with an immutable [CH(COOH)]/[IO ] = 1.5 value, where state I to state II transition occurs after a time delay and BR reaction ended with a solution abundant of solid iodine. The state I to the state II transition curves obtained at different temperatures were analyzed using the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory. The KJMA theory was applied for monitoring the crystallization process of isolated solid iodine product at various levels of operating temperatures. At T < 33.5 °C, we have one type of the process and iodine was formed by autocatalysis pathway. On the other hand, at T ≥ 33.5 °C, two processes occur. With the rise in operating temperature, the emergence of inhomogeneous distribution of nuclei was identified and it was established the primary and secondary crystallization processes of iodine. At elevated temperatures, it was also found that the strong influence of impingement mechanism exists. Results obtained are the first step toward elucidation of the complex reaction mechanism of the state I → state II transition. [ABSTRACT FROM AUTHOR]

The influence of adrenaline on two iodate based oscillating chemical reactions, the Bray-Liebhafsky (BL) and Briggs-Rauscher (BR) reactions was investigated. It was observed that the addition of adrenaline has different effects on the examined systems. Its addition to the BR system significantly changes the dynamics, while in the BL system, the presence of adrenaline does not show any effect. In order to find out the cause of such a different response of two similar oscillators, UV/VIS spectroscopy was used. Results obtained from recorded UV/VIS spectra indicated that, from all investigated stable reaction species, adrenaline interacts only with potassium iodate and iodine, which are present in both oscillating reactions. Because of this, the different response of the oscillators cannot be ascribed to the reactions between adrenaline and common iodine (stable and unstable) components. As a result, the considerable response of the BR system to adrenaline may be related to the reactions between adrenaline (or its oxidation products) and non-common derivatives of malonic acid or manganese intermediate species. [ABSTRACT FROM AUTHOR]

Due to the interesting and potentially useful properties, phosphate tungsten bronzes are constantly being studied and attract a lot of attention. In the present work, two different metallic elements, belonging to the group of rare-earth metals, cerium and praseodymium, were used as a dopants for phosphate tungsten bronzes. Novel cerium and praseodymium doped phosphate tungsten bronzes were successfully synthesized and further characterized by thermal analyses, Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometer and photoluminescence spectroscopy. The behavior of cerium and praseodymium doped phosphate tungsten bronzes were examined in the Briggs-Rauscher oscillatory reaction. The changes in the oscillatory dynamics, caused by the addition of cerium doped and praseodymium doped phosphate tungsten bronzes, are used for distinction of these bronzes and also as a method for testing the catalytic features of the bronzes. Beside the nonlinear behavior, the bronzes have shown photoluminescence in the visible region (blue region). [Display omitted] • Novel Ce and Pr doped phosphate tungsten bronzes (PWB) were synthesized. • Doped PWBs were characterized by TA, FTIR, XRPD, SEM with EDX and PL spectroscopy. • Ce and Pr PWB influence on the Briggs-Rauscher (BR) oscillatory dynamics is investigated. • BR is method used for testing catalytic properties of doped PWBs. • Potential application of material as blue light source for LEDs. [ABSTRACT FROM AUTHOR]

In this study, the antioxidant activity of aqueous and ethanolic solutions of ferulic, homovanillic and vanillic acids were evaluated using Briggs-Rauscher oscillating reaction method. This method is based on the inhibitory effects of antioxidants on the oscillations of the Briggs-Rauscher reaction mixture. The inhibitory effect consists of an immediate quenching of oscillations, an inhibition time that depends on the amount and type of the antioxidant added, and a subsequent regeneration of oscillations. Flow oscillations in the Briggs-Rauscher reaction mixture were followed potentiometrically. In all samples, the inhibition times increased with increasing concentration and linearity was found in a wide concentration range of phenolic acid added. The antioxidant activity decreased in following order: ferulic acid > homovanillic acid > vanillic acid. It was also investigated the antioxidant activity for two-component and threecomponent mixtures of aqueous solutions examined phenolic acids. [ABSTRACT FROM AUTHOR]

Abstract: Effect on the behavior of Tyrosine through a malonic acid (MA) based Briggs‐Rauscher (BR) oscillatory system was studied in order to understand the mechanistic details of thyroid metabolism in vitro, specifically the iodination of tyrosine. It was observed that the present BR system employing tyrosine as a main additive and malonic acid as substrate provides an example of entrainment oscillations, in which malonic acid is responsible for oscillations and in presence of tyrosine, the system showed different oscillatory behavior. The effects of various other chemical species such as SeO2, KSCN, KNO3, KBr and Fe(III) on the tyrosine in this malonic acid based BR system are studied. The study was supported by UV‐Visible spectrophotometry to study the interactions of these chemical species with Dushmann reaction, which is one of the important reaction steps in BR reaction mechanism, in order to investigate the key factors responsible for tyrosine iodination responsible for thyroxin formation. Needless to mention that, all the aforesaid chemical species have due role in normal thyroid metabolism in vivo and as such, the present BR system containing tyrosine as main (first) additive can help in understanding of thyroid metabolism. [ABSTRACT FROM AUTHOR]

The study involves the dynamic evolution of the Briggs-Rauscher (BR) reaction in the presence of various surfactants-SDS (sodium dodecyl sulphate) as anionic, CTAB (cetyl trimethylammonium bromide) as cationic and TritonX-100 [4-(1,1,3,3-(tetramethylbutyl) phenyl polyethylene glycol] as a neutral one in single as well as mixed mode conditions (SDS + TX-100 and CTAB + TX-100). The reaction has been monitored potentiometrically at 30 °C under CSTR conditions. These surfactants affect the reaction dynamics to an extent which depends on the nature and concentration of the surfactant and the formation of their self-assemblies. The experimental findings indicate that the oscillatory behavior of the BR reaction in the presence of surfactants is due to the efficacy of organized surfactant assemblies to selectively distribute the key species involved in the reaction, and their interaction with the counter ions in cases of ionic micelles. The study reveals that the evolution of oscillatory behavior is a characteristic feature of the surfactant. [ABSTRACT FROM AUTHOR]

Phenolic acids are secondary metabolites of aromatic plant that possess prominent antioxidant activity. When an antioxidant is added to an active oscillating Briggs-Rauscher reaction mixture, there is an immediate cessation of the oscillations, an inhibition time that linearly depends on the concentration of the antioxidant added, and a subsequent regeneration of oscillations. In this study, the effects of concentration of the ethanol solutions of selected phenolic acids (gallic, caffeic, chlorogenic, rosmarinic, p-coumaric and m-coumaric acids) on the oscillatory system Briggs-Rauscher reaction were investigated. The reaction was performed in a constantly stirred reactor, with accurately defined concentrations of reactants, at constant temperature of 25°C. Flow oscillations in the Briggs-Rauscher reaction mixture were monitored as a change in potential between the platinum electrode and silver/silver chloride reference electrode. Relative antioxidant activities of phenolic acids were determined in three ways on the basis of inhibition times. The obtained results showed that the gallic and p-coumaric acids have much less antioxidant activity than the caffeic, chlorogenic and rosmarinic acids. The ability to inhibit oscillations of the Briggs-Rauscher reaction mixture is not showed for m-coumaric acid. [ABSTRACT FROM AUTHOR]

Copyright of Works of the Faculty of Forestry University of Sarajevo is the property of Faculty of Forestry University of Sarajevo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Briggs-Rauscher oscillating reaction can be used as test for antioxidant activity of pure compounds or food extracts. Antioxidants are substances that have the ability to neutralize free radicals, which are harmful to human health. Adding the substances with antioxidant ability to the reaction mixture, oscillations temporarily stops, and after a certain time the oscillating reaction starts again. The period without oscillations is known as inhibition time, and it's proportional to the quantity of antioxidant species in reactive mixture. In this study the Briggs-Rauscher reaction was used to measure the antioxidant activity of chlorogenic acid. Inhibition time, duration of reaction and the number of oscillations was determined varying the concentration of chlorogenic acid and solvent (water, ethanol, dimethyl sulfoxide). Flow of oscillations in the Briggs-Rauscher reaction mixture was monitored as a change in potential between the platinum and silversilver chloride electrodes at room temperature. With increasing concentrations of chlorogenic acid in all three solvents the inhibition time of oscillations is increased. [ABSTRACT FROM AUTHOR]

This paper reports a method for evaluating antioxidant capacity based on the inhibitory effects of a macrocyclic Ni(II) complex-catalysed Briggs–Rauscher reaction. The macrocyclic Ni(II) complex NiL(ClO 4 ) 2 , in which L is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, is a porphyrin-like compound, the structure of which can be found in certain enzymes. The experiments indicated that three natural compounds could temporarily quench the oscillations for a period of time prior to regeneration of oscillations. The inhibition time was related to the compound type and concentration; thus, procedures for evaluating the antioxidant activities of polyphenolic compounds were successfully established. Three polyphenolic compounds were tested to evaluate their antioxidant activities: protocatechuic acid, rutin hydrate and procyanidin. Of these three naturally occurring compounds, procyanidin was found to be the most efficient antioxidant. We have also discussed the reaction of the antioxidant with the hydroperoxyl radical (HOO ) present in the oscillating system. [ABSTRACT FROM AUTHOR]

In order to propose mechanisms of complicated chemical systems, it is necessary to study simpler subsystems. The mechanism we have proposed for the Bray-Liebhafsky (BL) oscillating reaction is based on kinetic studies of several reactions of iodine compounds between them and with hydrogen peroxide. Because the reactants of the non-catalysed Briggs-Rauscher (BR) oscillating reaction are the same as those of the BL reaction plus malonic acid, we propose now to extend the mechanism of the BL reaction to the BR reaction. With this aim, we add radical reactions of iodine compounds and of malonic acid. The choice of these reactions is based on our recent study of the unusual kinetics of the iodate reduction by high concentrations of hydrogen peroxide. [ABSTRACT FROM AUTHOR]

The consumer's attention is increasingly attracted by a multitude of health claims floated from the biggest food industries about probiotics. To date, the European Food Safety Authority (EFSA) has rejected all the applications for their health claims because they were not evidence based. It follows that more studies to characterise these microorganisms are needed, for instance regarding their antioxidant activity against reactive oxygen species involved in a number of illnesses and ageing. Questions as to whether the results have any bearing on effectiveness in the human body demand new methods able to estimate the antioxidant activity in a way that mimics the physiological defence against free radicals. In the following, (i) we report on the optimisation of a method complying with these requests and compare it to the classical Folin-Ciocalteu assay, (ii) we assert and explain its eligibility as regards probiotics on the basis of the mechanism of their antioxidant activity and (iii) we apply this method to highlight for the first time that probiotic bacteria and potential pathogens share the antioxidant capacity even if to a different extent. We provided food scientists with a tool to let them make educated guesses concerning the selection of effective ingredients for the production of functional foods. [ABSTRACT FROM AUTHOR]

This paper reports a new method for determination of tracing amounts of eugenol (EUG) by its perturbation effects on a novel Briggs-Rauscher (BR) oscillating system catalyzed by a macrocyclic complex [NiL](ClO4)2. The ligand L in the complex is 5, 7, 7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. In this novel BR oscillator, not only a macrocyclic complex was used as a catalyst to replace Mn2+, but the value of pH in the system was kept at pH of stomach fluids (pH ≈2.0) as well. Experimental results have shown that addition of EUG into the BR system could quench and then successively regenerate the oscillations, accompanying by an inhibitory time that relies on the concentration of the EUG added. An assay was thus established by employing such a BR system for determining EUG. The relationship between inhibition time and EUG concentrations is obtained over the range between 5.00×10−7-2.50×10−5M. Two calibration curves are thus achieved: linear regression over the range 5.00×10−7 to 1.25×10−5M of EUG, and polynomial regression over the range 1.25×10−5 ~ 2.50×10−5M of EUG. The obtained RSD from seven measurements of 1.00×10−5M of EUG is 3.75%, and from 1.50×10−5M of EUG is 2.05%. Some factors influencing the determination were also examined. Not only has the method been successfully applied to determine EUG but it could be extended to determine other lipophilic antioxidants as well. Furthermore, the possible reaction mechanism using the FCA model has been proposed. [ABSTRACT FROM AUTHOR]

Perturbations with chemical species that have dissimilar physico-chemical properties, such as bromide ions, polyphenols or iron complexes, are often used to investigate the detailed molecular mechanism of the Briggs-Rauscher (BR) oscillating reaction. We describe in this review the effects caused by some of these species and present their mechanistic interpretations. Some new original results are also reported. [ABSTRACT FROM AUTHOR]

The effect of electromagnetic radiation with a frequency close to the maximum of absorption of atmospheric oxygen on the Briggs-Rauscher self-oscillating reaction is described. It is shown that the radiation intensifies oxygen production and lengthens the duration of the self-oscillating regime by more than 20%. [ABSTRACT FROM AUTHOR]

Abstract: The reaction between isatin and 2,5-dimethoxyaniline is described. The main product was identified as 3,3-bis(4-amino-2,5-dimethoxyphenyl)-1,3-dihydroindol-2-one. The antioxidant activity of the compounds isolated was evaluated with two methods. Three published antitumor E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones entered the same tests to search whether they are endowed with antioxidant activity too. 3,3-Bis(4-amino-2,5-dimethoxyphenyl)-1,3-dihydroindol-2-one and the three antitumor agents showed a good chemical antioxidant activity. [Copyright &y& Elsevier]

In this work, we describe the crazy-clock phenomenon involving the state I (low iodide and iodine concentration) to state II (high iodide and iodine concentration with new iodine phase) transition after a Briggs–Rauscher (BR) oscillatory process. While the BR crazy-clock phenomenon is known, this is the first time that crazy-clock behavior is linked and explained with the symmetry-breaking phenomenon, highlighting the entire process in a novel way. The presented phenomenon has been thoroughly investigated by running more than 60 experiments, and evaluated by using statistical cluster K-means analysis. The mixing rate, as well as the magnetic bar shape and dimensions, have a strong influence on the transition appearance. Although the transition for both mixing and no-mixing conditions are taking place completely randomly, by using statistical cluster analysis we obtain different numbers of clusters (showing the time-domains where the transition is more likely to occur). In the case of stirring, clusters are more compact and separated, revealed new hidden details regarding the chemical dynamics of nonlinear processes. The significance of the presented results is beyond oscillatory reaction kinetics since the described example belongs to the small class of chemical systems that shows intrinsic randomness in their response and it might be considered as a real example of a classical liquid random number generator. [ABSTRACT FROM AUTHOR]

The antioxidant capacities and the total phenolic content in cocoa liquor directly manufactured chocolate from an artisan manufacturer were measured using different in vitro methods (BR, TEAC, and Folin–Ciocalteu Reagent). These parameters were then compared with those of a chocolate made by a leading manufacturing company producing chocolate and cocoa-containing products. A statistical analysis of the collected data showed that the antioxidant properties of the artisan-made chocolate are significantly better than those of the factory-produced one. These results were ascribed to the fact that all the bioactive components in the cocoa beans are better preserved in the artisan-made chocolate. [ABSTRACT FROM AUTHOR]

Abstract: Perturbations of the oscillatory regime of the Briggs–Rauscher (BR) reaction by the iron(II)–phenanthroline (ferroin) complex were observed in batch conditions. The path of the perturbation (immediate quenching of oscillations – inhibition time – resumption of oscillations) is similar to that provoked by antioxidant free-radical scavengers; however, perturbations occur in a ferroin concentration range much lower than that in which antioxidants act. To investigate this effect, reactions between the iron(II)–or iron(III)–phenanthroline (ferriin) and reagents or intermediates of the BR system were studied in detail. Results of these studies showed that the interaction of the ferroin/ferriin couple with iodine production is responsible for the observed perturbation. A mechanistic interpretation involving HOO radical is proposed. [Copyright &y& Elsevier]

Abstract: Leontopodic acid—a novel full substituted hexaric acid derivative, was isolated from the aerial parts of Edelweiss (Leontopodium alpinum Cass.) as one of the major compounds. The complex structure of leontopodic acid-2-[(3S)-3-hydroxybutanoate]-3,4,5-tris-[(2E)-3-(3,4-dihydroxyphenyl)-2-propenoate]-d-glucaric acid—was elucidated by mass spectrometry, 1D- and 2D NMR spectroscopy and HPLC monitored transesterification. Leontopodic acid exhibited pronounced antioxidative effects in the Briggs-Rauscher (BR) model [(r.a.c.)m 3.4±0.5] and the trolox equivalent antioxidant capacity (TEAC) method (TEAC value of 1.53±0.11). The antioxidative properties of this compound were confirmed by the 3D method, an in vitro assay evaluating DNA protection against oxidative damage (IC50: 1.89μM). [Copyright &y& Elsevier]

Cynara scolymus leaves extracts have long been used in folk medicine for their choleretic and hepatoprotective activities, that are often related to the cynarin content. These therapeutic properties are also attributed to mono- and di-caffeoylquinic acids and since commercial C. scolymus preparations can differ for their activities, we studied four extracts to evaluate, if present, a relationship between the hepatobiliary properties of the different preparations and their content in phenolics. The antioxidant activity of the commercial preparations examined was also considered in an in vitro system. The results showed that the extract with the highest content in phenolic derivatives (GAE) exerted the major effect on bile flow and liver protection. Also the results of the antioxidant capacity (BR) of the different preparations are in good agreement with the results obtained in vivo. On the contrary, administering rats with doses of chlorogenic acid, equivalent to those present in this extract, we did not observe any choleretic or protective action. An histopathological analysis of liver sections confirmed the biochemical results. Perhaps caffeoyl derivatives have a role in the therapeutic properties of C. scolymus extracts, as reported in literature for “in vitro” studies, but when administered alone, they are not so effective in exerting this action. [Copyright &y& Elsevier]

• A novel kinetic method for identification of four halide ions was reported. • We utilized the B-R oscillator to distinguish halide anions for the first time. • Analysis could be finalized easily and quickly. • The method may be utilized for analysis of other ions as well. The current approach elaborates an innovative methodology for distinguishing four halide ions (F−, Cl−, Br− and I−) on their perturbation effects upon novel Briggs-Rauscher Reaction (BR) catalyzed by tetraaza-macrocyclic-nickel-complex (NiL)(ClO 4) 2. The lingand "L" in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11 -tetraazacyclotetradeca-4,11-diene). Different oscillating profiles were exposed while the equal addition of four halide ions separately into active BR over the concentration range of 5.0 × 10−5-2.375 × 10−4 mol/L. Fluoride (F−) ion does not affect BR. Chloride (Cl−) ion could quench the potential oscillation at high potential and regenerate oscillation after a short inhibition time (t in). Bromide (Br−) ion could merely diminish the oscillation amplitude (A) and oscillation period (T) with no inhibition time whereas the iodate (I−) ion can restrain the potential oscillation at low potential and regenerate oscillation after a short inhibition time (t in). These four halide ions could be distinguished within 7 min. Cyclic voltammetry (CV) confirmed the redox reaction of potassium iodate with analytes while the bromination or the iodination products were testified by using mass spectrometry (MS) analysis after the perturbation of Br− or I−. Finally, a reasonable explanation of the perturbation mechanism for the BR was proposed based on well-known NF and FCA models. [ABSTRACT FROM AUTHOR]

Briggs-Rauscher (BR) oscillatory reaction is a chemical system very sensitive to different analyte addition. Changes in oscillatory dynamics, by analyte addition, could be successfully used for the determination of analyte concentration, as well as for its antioxidative/antiradical activity assessment. In this work, the BR reaction is used as a system detector for distinguishing solid unsolvable materials, such as phosphate tungsten bronze (PWB) and phosphate molybdenum bronze (PMoB), obtained by thermal treatment. The addition of different masses of PWB in BR reaction decreases its oscillation time, while the addition of different masses of PMoB had no effects on the BR oscillation time. Additionally, the BR oscillation time is the linear function of added PWB mass. The mechanism of bronzes action is investigated by using pH and electric conductivity measurements, as well as inductively coupled plasma and the cyclic voltammetry measurements, and it can be ascribed to PWB better catalytic activity then PMoB, under BR reaction condition. This work extends the practical aspect of the BR reaction for testing solid (insoluble) materials, and opening the possibility of using oscillatory reactions in material science and catalysis, in general. Unlabelled Image • Insoluble PWB linearly decreases the BR oscillation time. • Insoluble PMoB had no effects on the BR reaction. • Obtained behavior can be successfully used to distinguish PWB and PMoB. • PWB has identical role as metal catalyst Mn2+ in BR reaction. • Extension of BR reaction practical aspect to material science and catalysis. [ABSTRACT FROM AUTHOR]

The antioxidant activity of some spices was determined using the Briggs- Rauscher oscillating reaction. Five spices: basil, dill, ginger, oregano and rosemary were used as samples. Spices were available in the local markets. All tested samples were prepared by boiling 0.1g of spices with 25 mL distilled water at 90-95°C for 5 and 10 minutes. The inhibition times produced by spice extracts on an active Briggs- Rauscher oscillating reaction mixture were recorded potentiometrically at 20°C. The antioxidant activity was expressed as the inhibition time of Briggs-Rauscher oscillating reaction. Preliminary studies showed that extracts of all spices except dill obtained by boiling for 10 minutes have less antioxidant activity than the corresponding extract obtained by boiling for 5 minutes. The best ability to inhibit oscillations of the Briggs-Rauscher reaction mixture i.e. the highest antioxidant activity showed an extract of basil obtained by boiling for 5 minutes, and the lowest activity showed an extract of rosemary obtained by boiling for 10 minutes. [ABSTRACT FROM AUTHOR]

Ruthenium complexes attract huge attention over the past decades due to their biological, catalytic, electronic and optical properties. In this study, the effect of ruthenium complexes of the general formula [Ru(N-Ph-5-X-salim)2(ind)2]Cl (where X=H, Cl or Br; ind=indazole) on the Briggs-Rauscher oscillating reaction was investigated. The oscillations in the Briggs-Rauscher reaction mixtures were followed potentiometrically. Addition of ethanolic solutions of tested complexes to an active Briggs-Rauscher reaction mixture caused an immediate effect of quenching of oscillations. After the inhibition time, the oscillations were restarted with amplitude and frequency different in a reference mixture. A linear correlation between the inhibition time and the concentration of the complexes added to the Briggs-Rauscher reaction mixture were found in the range from 5.36 to 21.0 μmol/L. The ability of complexes to inhibit oscillations of the Briggs-Rauscher reaction mixture is similar to that caused by antioxidant free radical scavengers. The obtained preliminary results suggest further analyses of this effect. [ABSTRACT FROM AUTHOR]

Coffee is one of the most commonly consumed hot beverages in Bosnia and Herzegovina. The positive effect of coffee consummation on human health is usually attributed to bioactive substances found in coffee that have antioxidant activity. The antioxidant activity of coffee depends on several factors such as geographic origin and the type of coffee, storage and roasting of green coffee, preparation method of the coffee drink and a variety of additives. In this paper, the Briggs-Rauscher oscillating reaction is used to assess the antioxidant activity of twelve different samples of coffee available in the local markets. All tested samples of coffee were prepared in the same manner by boiling for 5 minutes. The Briggs- Rauscher reaction system consisted of appropriate ratio of aqueous solution of hydrogen peroxide, potassium iodate, manganese(II) sulfate, malonic acid, sulfuric acid and starch as indicator. Changes in the Briggs-Rauscher reaction mixture were monitored as a change in potential between the platinum electrode and the silversilver chloride electrode at room temperature. The addition of antioxidants in the Briggs-Rauscher reaction mixture leads to immediate shutdown of oscillation. Inhibition time i.e. the time to stop the oscillation is proportional to the amount and properties of added antioxidants. Tested samples of coffee showed different times of inhibition. The best ability to inhibit oscillations i.e. the highest antioxidant activity showed a sample of 100% Arabica, and the lowest activity sample of instant coffee known as 3 in 1. [ABSTRACT FROM AUTHOR]

The Briggs-Rauscher oscillating reaction can be used as test for antioxidant activity of pure compounds and food extracts which are consumed daily, like fruits, vegetables, juices, etc. By addition of substances with antioxidant ability to the Briggs-Rauscher reaction mixture, there is an immediate quenching of oscillations, and after a certain time the oscillations start again. The time of no oscillations or inhibition time is proportional to the amount of the antioxidant added. In this study, the Briggs-Rauscher reaction was used to determine antioxidant activity of extracts of selected medicinal plants: rosemary (Rosmarinus spp.), savory (Satureja spp.), mountain tea (Sideritis spp.) and hibiscus (Hibiscus spp.). The plant extracts were prepared by the process of maceration with water and ethanol as solvent, at room temperature. The Briggs-Rauscher reaction was performed in a stationary, constantly stirred reactor with an accurately defined concentrations of reactants at temperature of 25°C. Changes in the Briggs-Rauscher reaction mixture were followed potentiometrically with platinum and silver-silver chloride electrodes. Preliminary studies have shown that ethanolic extracts of rosemary, mountain tea and hibiscus have much less antioxidant activity than the corresponding aqueous extract, while the ethanolic extract of savory had greater antioxidant activity than aqueous extract. Aqueous extract of mountain tea showed the best ability to inhibit oscillations, i.e. the highest antioxidant activity comparing to all other samples. [ABSTRACT FROM AUTHOR]