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DPPH radical

In this contribution it is shown that local density functional (LDF) theory accurately predicts structural and electronic properties of metallic systems (such as W and its (001) surface) and covalently bonded systems (such as graphite and the ethylene and fluorine molecules). Furthermore, electron density related quantities such as the spin density compare excellently with experiment as illustrated for the di-phenyl-picryl-hydrazyl (DPPH) radical. Finally, the capabilities of this approach are demonstrated for the bonding of Cu and Ag on a Si(lll) surface as related to their catalytic activities. Thus, LDF theory provides a unified approach to the electronic structures of metals, covalendy bonded molecules, as well as semiconductor surfaces. [Pg.49]

The calculation of the spin density in the DPPH radical demonstrates that quantities related to the charge distribution of electrons are very well described by this approach. The spin-density is a particularly sensitive test as it is the difference of two large quantities, namely the electron densities of each spin system. [Pg.65]

DPPH radical Electron spin resonance spectrometry Spectrophotometry (515-528 nm) Spectrophotometry/HPLC... [Pg.272]

Liu JK, Hu L, Dong ZJ and Hu Q. 2004. DPPH radical scavenging activity of ten natural p-terphenyl derivatives obtained from three edible mushrooms indigenous to China. Chem Biodiv 1 (4) 601—605. [Pg.299]

Nevertheless, all of the extracts revealed to exhibit of no consequence antioxidant property against DPPH radical at 0.2 mg/ml with the highest inhibition of 44.1% from LC-CHClj-Alk, when compared to BHA, whose inhibition was 92.7% (Table 8.3). [Pg.102]

Table 8.3 Antioxidant activity of the LC extracts against DPPH radical at 0.2 mg/ml... Table 8.3 Antioxidant activity of the LC extracts against DPPH radical at 0.2 mg/ml...
The DPPH radical terminates other radicals, probably by the reaction... [Pg.233]

The radical scavenging methods require the general caution that the stoichiometry of the reaction between scavenger and radical must be established. A problem with some scavengers is that their reaction with radicals may not be quantitative. The DPPH radical is an extremely efficient scavenger in many systems. It completely stops vinyl acetate and styrene polymerizations even at concentrations below 10 4M [Bartlett and Kwart, 1950]. However, the scavenging effect of DPPH is not universally quantitative for all monomers. [Pg.234]

The addition of known radical scavengers such as the DPPH radical to a polymerizing system will halt polymerization if it is a radical reaction. Ionic polymerizations will be unaffected by such additions. One must be careful, however, not to use a radical scavengers that also affects ionic polymerization. Thus, benzoquinone would be a poor choice as a radical scavenger, since it can also act as an inhibitor in ionic polymerization. [Pg.444]

In vitro tests, used in evaluation of antioxidant properties make use of the ability of antioxidants to quench free radicals. Based on this mechanism, the methods are divided into two groups SET - single electron transfer, and HAT - hydrogen atom transfer. Reactions with antioxidants in assays with the DPPH radical, ABTS and the Folin-Ciocalteu reagent both operate according to the SET and HAT mechanism. Due to the kinetics of the reaction, they are included in the... [Pg.102]

Analysis of antioxidant properties relative to the DPPH" radical involves observation of colour disappearance in the radical solution in the presence of the solution under analysis which contains antioxidants. A solution of extract under analysis is introduced to the environment containing the DPPH radical at a specific concentration. A methanol solution of the DPPH radical is purple, while a reaction with antioxidants turns its colour into yellow. Colorimetric comparison of the absorbance of the radical solution and a solution containing an analysed sample enables one to make calculations and to express activity as the percent of inhibition (IP) or the number of moles of a radical that can be neutralised by a specific amount of the analysed substance (mmol/g). In another approach, a range of assays are conducted with different concentrations of the analysed substance to determine its amount which inactivates half of the radical in the test solution (ECso). The duration of such a test depends on the reaction rate and observations are carried out until the absorbance of the test solution does not change [4]. If the solution contains substances whose absorbance disturbs the measurement, the concentration of DPPH radical is measured directly with the use of electron paramagnetic resonance (EPR) spectroscopy. [Pg.103]

Glavind and Holmer proposed a method of determination of antioxidants by TLC using the DPPH radical. They sprinkled a plate with separated substances with methanol solutionofthe radical and observed discoloration where substances able to quench radicals were present [57]. The TLC-DPPH assay allows a researcher to access the analysed substances and to assess the biological activity of individual compounds. Another advantage of the method is the possibili-... [Pg.110]

Initially, the use of HPLC in analysis of antioxidant properties with the DPPH" radical was restricted to chromatographic analysis of the radical content in solution. An assay was performed in which a solution of the radical was treated with the extract under analysis. The reaction ran in a reaction tube and the remainder of the radical after the reaction was analysed chroma-tographically. A comparison of the radical content in the blank sample and in the extract sample showed the amormt of radical that was quenched by antioxidants in the analysed sample [62, 63].However, themethoddidnotprovidemoreinformation than the colorimetricmethod. Much better results are obtained in a post-column on-line reaction in which substances separated on a chromatographic column react with a radical in a reaction coil. [Pg.111]

Figure 6. UV and DPPH radical quenching chromatogram of a plant methanolic extract. Figure 6. UV and DPPH radical quenching chromatogram of a plant methanolic extract.
Marxen K, Vanselow KH, Lippemeier S, Hintze R, Ruser A, Hansen U-P. Determination of DPPH Radical Oxidation Caused by Methanolic Extracts of Some Microalgal Species by Linear Regression Analysis of Spectrophotometric Measurements. Sensors. 2007 7, 2080-2095. [Pg.116]

Many EOs also exhibit antioxidant activity and therefore several studies have been carried out in order to elucidate the activity of the components [139,153]. For instance, y-terpinene retarded the peroxidation of linoleic acid [139, 154-156], sabinene showed strong radical-scavenging capacity [139, 157], a-pinene [158] and limonene [146] showed low antioxidant activity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test, while terpinene and terpinolene showed high hydrogen-donating capacity against the DPPH radical [146, 150, 155, 158],... [Pg.92]

In another study conducted on marine zooplankton (Byun et ah, 2009b), antioxidant activity was measured for the DPPH radical of hydrolysates produced by Alcalase, a-chymotrypsin, Neutrase, papain, pepsin, and trypsin. To identify antioxidant peptides, peptic hydrolysate was purified using consecutive chromatographic methods, and antioxidant peptides were identified to be Leu-Leu-Gly-Pro-Gly-Leu-Thr-Asn-His-Ala (MW 1076Da) and Asp-Leu-Gly-Leu-Gly-Leu-Pro-Gly-Ala-His (MW 1033Da) by Q-TOF ESI mass spectroscopy. IC50 values of purified peptides were... [Pg.62]

Sugiyama, Y., Ito, Y., Suzuki, M., and Hirota, A. (2009). Indole Derivatives from a marine sponge-derived yeast as DPPH radical scavengers. ]. Nat. Prod. 72, 2069-2071. [Pg.152]

Nakajima, K., Yoshie-Stark, Y., and Ogushi, M. (2009). Comparison of ACE inhibitory and DPPH radical scavenging activities of fish muscle hydrolysates. Food Chem. 114,844—851. [Pg.259]

Fig (10). Scavenging activity of flavonoids from/., licaniaeflora leaves on DPPH radical. [Pg.65]


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1,1 -Diphenyl-2-picrylhydrazyl radical DPPH)

DPPH

DPPH free radical

DPPH free radical scavenging

DPPH free radical scavenging activity

DPPH free radical-scavenging assay

DPPH radical scavenging activity

DPPH radical scavenging assay

Free radical inhibitors DPPH and Galvinoxyl

Free radical scavenging DPPH radicals

Peroxidation inhibition DPPH) radicals

Radicals reaction+DPPH

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