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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]

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]

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]

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]

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]

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]