DPPH free radical

BONDET v, BRAND-wiLLiAMS w and BERSET c (1997) Kiuetics and mechanisms of antioxidant activity using the DPPH- free radical method, Lebensm Wiss Technol, 30, 609-15. 

Liu D, Shi J, Ibarra AC, Kakuda Y and Xue SJ. 2008. The scavenging capacity and synergistic effects of lycopene, vitamin E, vitamin C, and (1-carotene mixtures on the DPPH free radical. Food Sci Technol 41 1344-1349. 

Villano D, Fernandez-Pachon MS, Moya ML, Troncoso AM and Garcia-Parrilla MC. 2007. Radical scavenging ability of polyphenolic compounds towards DPPH free radical. Talanta 71(1) 230—235. 

Abstract Recently, we have investigated Aconitum cochleare Woroschin and obtained three new alkaloids cochleareine, acoleareine from the aerial parts of the plant and cochleareinine from the roots. Cochlearenine exhibited antioxidant activity against DPPH free radical scavenging assay. The cardio active effect of has also have been studied on isolated heart preparations. 

Bondet V, Brand-Williams W, Berset C. Kinetics and Mechanisms of Antioxidant Activity using the DPPH" Free Radical Method. Food Science and Technology. 1997 30, 609-615. 

Noipa T, Srijaranai S, Tuntulani T, Ngeontae W. New approach for evaluation of the antioxidant capacity based on scavenging DPPH free radical in micelle systems. Food Research International. 2011 44(3) 798-806. 

Wettasinghe M, Shahidi F. Scavenging of reactive-oxygen species and DPPH free radicals by extracts of borage and evening primrose meals. Food Chemistry. 2000 70 17-26. 

Jothy ST, Zuraini Z, Sasidharan S. Phytochemicals screening, DPPH free radical scavenging and xanthine oxidase inhibihory activihes of Cassia fistula seeds extract. Journal of Medicinal Plants Research. 2011 5(10) 1941-1947. 

DPPH Free Radical Blois (53) showed that a,a-diphenyl-p-picrylhydra-zyl radical (DPPH ) can be used for determining antioxidant activity of ascorbic acid, tocopherol, and quinones (Figure 8a and b). DPPH in ethanol shows a strong absorption band at 517 nm (independent of pH from 5.0 to 6.5), and the solution appears to be deep violet in color. As the DPPH radical is scavenged by the donated hydrogen from the antioxidant, the absorbance is diminished according to the stoichiometry. 

Most stilbenoids possess antioxidant activities because they possess polyphenol functions in the molecules. Some of their beneficial effects, hepatoprotective action, cardiovascular protection, for instance, are in close relation to their antioxidant activities. Several models have been employed in the assay such as lipid peroxidation system, human low-density lipoprotein model, xanthine oxidase system and l,l-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging model, which is the most commonly used protocol. 

Recently, Youssef et al. [24] reported the synthesis of curcumin analogs as potential antioxidant and cancer chemopreventive agents. The general structures of the synthesized analogs are shown in Fig. (8). These compounds were tested for scavenging ability of DPPH free radicals and in an ATP chemiluminescence assay. The SAR conclusions from the results were mainly consistent with the prior conclusions drawn by other researchers. In addition, they found that di-substitution of the central methylene group resulted in decreased antioxidative activity. 

Several studies described the interaction of flavonoids with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical [76, 79, 107-108] (Fig. (3)). DPPH is a stable free radical and is frequently used in ESR studies [109]. The DPPH assay provides information on the reactivity of flavonoids with a stable free radical [79]. Because of its odd electron, DPPH gives a strong absorption band in ethanol at 517 nm. As this... 

Fig. (3). Structure of the l,l-diphenyl-2-picrylhydrazyl (DPPH) free radical.

The number of lines in the ESR spectrum of a radical is a clue to its identity. Of further assistance is the intensity pattern in the spectrum. For n equivalent nuclei with 7 = 1/2, the n + 1 lines have intensities proportional to the binomial expansion of order n. Table 13.2 lists the relative intensities up to n = 5. The intensity patterns for sets of equivalent nuclei with 7 > 1/2 are handled in a similar fashion. Figure 13.5 shows the ESR spectrum of diphenylpicrylhydrazyl (DPPH) free radical in benzene. Under low-resolution conditions, the proton hyperfine coupling is not observed and the five-line spectrum with the intensity distribution 1 2 3 2 1 results from the interaction of the unpaired electron with two (effectively equivalent) (7=1) nuclei for nuclei with 7 > 1/2, the intensity distribution is more complex than a simple binomial expansion, and is beyond the scope of this text. 

Electron spin resonance (ESR) spectrometry measures the presence of unpaired electrons and is a widely accepted method for investigating antioxidant-radical reactions. A few ESR studies have been conducted to investigate the CLA reactions with 1,1-diphenyl-2-picrylhydrazyl (DPPH ) free radical in toluene (7,8). DPPH is... 

Antioxidant activity of petroleum ether, chloroform, ethyl acetate and methanol extracts of Usnea pictoides lichen was determined by DPPH free radical scavenging assay and ferric reducing assay (Pavithra et al. 2013). The scavenging potential of methanol extract was higher than other extracts, and also, in ferric reducing assay, methanol extract showed stronger reducing power than other extracts. 

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