1-1-diphenyl-2-picrylhydrazyl and acetonitrile

2,2-Diphenyl-1-picryl-hydrazyl (DPPH) radical decomposition in alcohol solution is widely used, characterizing plant antioxidants that can rise in serum after fruit and vegetable intake. However, this test failed reproducible results with serum due to protein precipitation. We describe the application of serum deproteinization with acetonitrile relating to the DPPH test.. Assay sensitivity, linearity, repeatability and storage effect were determined in serum samples deproteinized with an equal volume of acetonitrile. Associations between the DPPH test and the ferric reducing ability of serum (FRAP) method, measuring total antioxidant potential, were evaluated in sera from 78 healthy non-smoking men. The effect of a single ingestion of 1 L of cloudy apple juice on the serum DPPH radical scavenging activity in healthy volunteers was also investigated.. Assay linearity was within 5-25 microL (r=0.99, p<0.01). With 25 microL-deproteinized serum, coefficient of variation was 4.2% and detection limit was 0.5% of the initial amount of decomposed DPPH radical over 30 min incubation. There was no sera activity decrease over 14 days storage at -20 degrees C. Mean values of DPPH radical scavenging activity and FRAP obtained in human serum were 11.2+/-3.3% and 382.0+/-88.1 micromol/L, respectively. A positive significant linear correlation was observed between these two methods (r=0.42, p<0.01). Serum supplementation with 50 micromol/L of catechin, gallic acid, ascorbic acid or uric acid enhanced DPPH test results. One brisk serving of 1 L of apple juice caused a significant increment of serum DPPH radical scavenging activity (1.9+/-1.9%, p<0.01) in 12 healthy subjects 1 h after juice ingestion.. Applicability of the DPPH test to deproteinized serum with acetonitrile revealed numerous advantages, validating its practicability, simplicity and cost effectiveness as a tool in the estimation of antioxidant status in humans.

Topics: Acetonitriles; Adult; Albumins; Antioxidants; Beverages; Biphenyl Compounds; Chemical Precipitation; Female; Ferric Compounds; Food; Free Radical Scavengers; Humans; Linear Models; Male; Malus; Middle Aged; Oxidation-Reduction; Picrates; Reproducibility of Results; Sensitivity and Specificity; Specimen Handling; Temperature

The present work aimed to synthesise promising antioxidant compounds as a valuable alternative to the currently expensive and easily degradable molecules that are employed as stabilizers in industrial preparation. Taking into account our experience concerning domino Friedel-Crafts/lactonization reactions, we successfully improved and extended the previously reported methodology toward the synthesis of 3,3-disubstituted-3

Topics: Acetonitriles; Alkylation; Antioxidants; Benzofurans; Biphenyl Compounds; Electrochemistry; Kinetics; Methanol; Oxidation-Reduction; Phenols; Picrates; Regression Analysis; Solvents

Electron-transfer disproportionation of a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙) occurred in the presence of Sc(3+) acting as a strong Lewis acid in deaerated acetonitrile. In contrast, in the case of weaker Lewis acids than Sc(3+), such as Mg(2+) and Li(+), external protons from acetic acid were required for the disproportionation of DPPH˙ to occur.

Topics: Acetic Acid; Acetonitriles; Biphenyl Compounds; Catalysis; Lewis Acids; Magnesium Compounds; Mesylates; Perchlorates; Picrates; Reactive Oxygen Species; Scandium

A sensitive on-line DPPH-CE-DAD method was developed and validated for both screening and determining the concentration of seven antioxidants of Reduning injection. The pH and concentrations of buffer solution, SDS, β-CD and organic modifier were studied for the detection of DPPH and seven antioxidants. By on-line mixing DPPH and sample solution, a DPPH-CE method for testing the antioxidant activity of the complex matrix was successfully established and used to screen the antioxidant components of Reduning injection. Then, antioxidant components including caffeic acid, isochlorogenic acid A, isochlorogenic acid B, isochlorogenic acid C, chlorogenic acid, neochlorogenic acid and cryptochlorogenic acid were quantified by the newly established CE-DAD method. Finally, the total antioxidant activity and the multiple active components were selected as markers to evaluate the quality of Reduning injection. The results demonstrated that the on-line DPPH-CE-DAD method was reagent-saving, rapid and feasible for on-line simultaneous determination of total pharmacological activity and contents of multi-components samples. It was also a powerful method for evaluating the quality control and mechanism of action of TCM injection.

Topics: Acetonitriles; Antioxidants; beta-Cyclodextrins; Biphenyl Compounds; Calibration; Drugs, Chinese Herbal; Electricity; Electronics; Electrophoresis, Capillary; Hydrogen-Ion Concentration; Inhibitory Concentration 50; Injections; Limit of Detection; Online Systems; Picrates; Reference Standards; Temperature; Time Factors

This work evaluates the reduction kinetics of the antiradical probe 2,2-diphenyl-1-picrylhydrazyl (DPPH (*)) in methanol and acetonitrile by the antiradical activity of protocatechuic acid (3,4-dihydroxybenzoic acid, 1) and protocatechuic acid methyl ester ( 2). The reduction kinetics of DPPH (*) in both solvents by the antiradical activity of the p-catechol group in 2 is regular, that is, coincide with the proposed standard kinetic model for the reduction kinetics of DPPH (*) by the antiradical activity of an isolated p-catechol group. Therefore, the antiradical activity of 2 experimentally exhibits two rate-two stoichiometric constants in acetonitrile and three rate--three stoichiometric constants in methanol. In contrast, the reduction kinetics of DPPH (*) in both solvents by the antiradical activity of the p-catechol group in 1 is perturbed, that is, deviate from the proposed standard kinetic model. The deviations arise from the presence of the reactive carboxylic acid function which, in methanol, induces an additional reversible side reaction and, in acetonitrile, turns an irreversible reaction reversible, thus modifying the otherwise regular reduction kinetics of DPPH (*) by the antiradical activity of the p-catechol group in 1. On the other hand, the approximated theoretical kinetic equation that applies for those p-catechol groups whose reduction kinetics is regular and that experimentally exhibit three rate--three stoichiometric constants has been derived and used for fitting.

Topics: Acetonitriles; Biphenyl Compounds; Free Radical Scavengers; Hydroxybenzoates; Kinetics; Methanol; Models, Chemical; Molecular Structure; Oxidation-Reduction; Picrates