1,1 -Diphenyl-2-picrylhydrazyl DPPH radical

The reduction of the stable 1,1 -diphenyl-2-picrylhydrazyl radical (DPPH) has been used to assess the efficiency of antioxidants in beverages (Larrauri et al, 1999 Porto et al, 2000), vegetable oils (Espin et al, 2000) and of pure phenolic compounds (Madsen et al, 2000), reaction [16.17] ... 

Azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) (Fig. 1) and a,a -diphenyl-(3-picrylhydrazyl radical (DPPH) are the two most commonly used synthetic compounds in antioxidant activity determinations. ABTS, when oxidized by the removal of one electron, generates a metastable radical. The ABTS radical cation (ABTS" ) has a characteristic absorption spectrum with maxima at 411,... 

ROS scavenging ability of ERG was tested using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) solution-based chemical assay and a 2,2,7,2-dichlorodihydrofluorescein diacetate (DCFH-DA) HL-60 cell line-based assay. The cell-based fluorescent DCFH assay enables detection of antioxidant molecules which can penetrate cell membranes and inhibit ROS production in living cells. The antioxidant activity was determined by TPA-stimulated control cells with and without FRG. FRG showed strong antioxidant activity in both systems [64]. 

To provide samples for 2,2-Diphenyl-l-picrylhydrazyl radical (DPPH) assay, 500 g (wet weight) of berries were separated into peels, solids and juice. Both the peels and the solids were dried then extracted first with ethyl acetate (300 mL) and then with methanol containing 0.25 % formic acid (300 mL). The juice was extracted with ethyl acetate (400 mL) and the remainder lyophilized as the aqueous extract. Yields are given in Table V. 

Com oil phenols have been studied with respect to their potential to scavenge the free radicals, the peroxyl radicals, the superoxide radicals, etc. The free radical scavenging activity of the phenolic acids using model free radicals such as l,7-diphenyl-2-picrylhydrazyl radical (DPPH ), or ABTS (2,2 -azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt cation radical) is often measured. TEAC (Trolox equivalent antioxidant capacity), FRAP (Ferric-reducing antioxidant capacity) and TRAP (total-radical-trapping antioxidant parameter) of the com oil are also used in order to obtain additional information, necessary to investigate the relation between the antioxidant intake and the oxidative stress related diseases (Stratil et al., 2008 Ceto et al., 2014 Apak et al., 2007). 

The 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method was used to investigate the scavenging activity of tea samples. The data for DPPH free radical scavenging activity, measured as scavenging percentage at room temperature after addition of various fermented tea infiisions are presented in Figure 3. DPPH free radical scavenging activity of tea infusion inoculated with A. aceti and A. xylinum increased with incubation time up to 22.1% and 21.9%,... 

Radical Generation. The ESR spectrometer, flow system, and general procedure have been described (46). The apparatus was calibrated with freshly prepared diphenyl picrylhydrazyl (DPPH) solutions. The peroxy radical concentrations were determined by double integration of derivative spectra. A standard coal sample in the dual cavity allowed corrections to be made for changes in cavity Q. The rates of decay of the less reactive radicals were determined by stopped-flow techniques with manually or electrically operated valves. The decay was recorded... 

Popular EPR-based assays of antioxidant activity include the DPPH assay, in which the ability of compounds to quench (by H-atom transfer) the 1,1-diphenyl-2-picrylhydrazyl radical is used to rank their antioxidant activity. This method has been applied widely to the analysis of dietary antioxidants and extracts from medicinal plants.213 219 Extensive use has also been made of assays based on the competition between spin traps and test compounds for reaction with enzymatically-generated 02 and, in the presence of a metal catalyst, the OH rad-... 

DNAP, DNA-dependent DNA polymerase DNAS, DNA synthesis DPPH, 1,1 -diphenyl-2-picrylhydrazyl radical... 

Famesylhydroquinone 335, which exhibited DPPH (1, l-diphenyl-2-picrylhydrazyl) radical scavenging activity, was separated from Penicillium sp. marine fiingi and the method of the preparation of this compound was described. 

Other experimental studies carried out with a different radical, DPPH (7, l-diphenyl-2-picrylhydrazyl radical), revealed that oleuropein and hydroxy-tyrosol elicit a good, concentration-dependent, scavenging effect... 

As is generally known, electron spin resonance reveals the presence of unpaired electrons. This is of course characteristic of free radicals and the most well known stable free radical is a, a -diphenyl- -picrylhydrazyl(DPPH) (1, 213). In the ESR spectrum it gives a narrow signal close to free spin value g = 2.0036 and is used for calibrating the magnetic Held [2]. 

Experiments of disappearance of DPPH (2,2 diphenyl-l-picrylhydrazyl radical), which is widely used to test the ability of compounds to act as free radical scavengers or as hydrogen donors at different temperatures, are shown in Figure 1. Fresh distilled styrene or styrene and recently sublimated MA and a solution 10 M of DPPH were put in a vial in the presence OH-TEMPO or without it, and heated at 80°, 100° or 120 °C after oxygen had been... 

Note 5 On applying the DPPH assay, the determined ICj value for arbutin ( 768 mM) represents a 176 times lower antioxidant capacity than the one determined for quercetin (4.36 mM). Although the arbutin ICj(, value correlates well with those published by other investigators applying similar DPPH-assay conditions [23], it should be pointed out that there is an experimental conflict The DPPH assay, which uses alcohols (methanol) as the l,l-diphenyl-2-picrylhydrazyl-radical dissolvent, is preferably used to investigate the antioxidant capacity of lipophilic (alcohol... 

The results obtained for the antioxidant capacity determination of the edible oils by CL were compared with those obtained by a standard DPPH test, but the results were not comparable. One of the possible explanations for these differences is the nature of the free radicals employed in the determinations. In the DPPH test, the 2,2-diphenyl-l-picrylhydrazyl radical, a very voluminous compound, is used, and its reaction with the antioxidants may be affected by steric impediments. In the case of the CL method, the small reactive oxygen species generated from the Fenton s reagent are the species that react with antioxidants, and they are also responsible for the luminol CL. Moreover, the DPPH test measures the antioxidant activity of the hydrophilic and hydrophobic compounds present in the oil, while the CL method accounts especially for the hydrophilic fraction. 

A spectrophotometric method based on reduction of Mo(VI) to Mo(V) has been developed for the quantitative determination of the total antioxidant capacity of hexane extracts of com and soybean samples (Prieto et al., 1999). The antioxidant activity of methanohc corncobs extracts was measured based on their ability to scavenge the DPPH (2,2-diphenyl-l-picrylhydrazyl) radical (Sultana et al., 2007). This assay is based on radical disappearance according with sample antioxidant capacity (Figure 10). 

A first simultaneous EPR and visible spectropho-tometric study is reported on the interaction of the stable free radical l,l-diphenyl-2-picrylhydrazyl (DPPH) dissolved in ethanol with thioglycolic acid (HSCH2CO2H, TGA). The results of the kinetic studies at room temperature allow us to assume 1 1 stoichiometry of the reaction between DPPH and TGA giving l,l-diphenyl-2-picrylhydrazine (DPPH) and thioglycolic disulfide. The linear plots of EPR and UV-visible responses versus the quantity of added TGA are used to find the DPPH molar absorptivity at 520 nm to be 12350 3% Imol cm which may be used as a criterion for the purity of the material itself. It was also found that the paramagnetic and optical properties of a 30-year old sample gave results suggesting that in the solid state DPPH is a fairly stable material. 

The radical scavenging activity of PET was determined by using the stable radical DPPH (l,l-diphenyl-2-picrylhydrazyl). In a final volume of 300 pL, the reaction mixture contained 167 pM DPPH and PET (the powder was initially dissolved in water and finally diluted in 10% ethanol). After IS-min incubation in an incubator shaker, the absorption at 517 nm was taken and the value was corrected against a blank without DPPH (23). The radical scavenging activities of catechins, probucol, and trolox were also determined for comparison. 

---