Showing papers on "DPPH published in 1997"
TL;DR: In this paper, the reaction mechanisms of three antioxidants are proposed in order to explain experimental results obtained from a kinetic study using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, previously adapted in our laboratory.
Abstract: The reaction mechanisms of three antioxidants are proposed in order to explain experimental results obtained from a kinetic study using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH . ) method, previously adapted in our laboratory. In its radical form, DPPH . shows an absorbance maximum at 515 nm which disappears upon reduction by an antiradical compound. BHT, a synthetic antioxidant, slowly reacts with DPPH . reaching a steady state within 5 h. This 2.8-stoichiometric complete reaction follows a 1.5-order with respect to DPPH . and 0.5 to BHT. The kinetic rate constant, k, is estimated to be 5.0 L/(mol·s) at 20 °C and the energy of activation, Ea , is equal to 35 kJ/mol in methanol. Eugenol reacts with DPPH . reaching a steady state within 2 h. This 1.9-stoichiometric reaction follows a 2-order with respect to both DPPH . and eugenol, k and Ea are estimated to be 5.4 × 10 10 L 3 /(mol 3 ·s) at 20 °C and 30 kJ/mol, respectively. The eugenol mechanism may involve a dimerization between two phenoxyl radicals. The reaction with isoeugenol is rapid and reversible, with a stoichiometry of 1.1. It is first order with respect to isoeugenol with k (direct reaction) equal to 8.9 × 10 −2 s −1 at 10 °C. This reaction is consistent with a pseudo-monomolecular mechanism.
1,126 citations
TL;DR: There is a relationship between antioxidant potency and the total phenolic groups content in each extract, and Methanolic extracts are more potent as scavengers of peroxyl and superoxide radicals than the ethyl ether extracts.
Abstract: The antioxidant activities of methanol and ethyl ether extracts obtained from Thymus zygis, collected during the flowering or non-flowering period, were evaluated and compared. To investigate this potential, extracts were tested on their capacity to react with diphenylpicrylhydrazyl (DPPH) in a homogeneous medium, and to inhibit Fe2+/ascorbate-induced membrane lipid peroxidation, as estimated by the formation of thiobarbituric acid-reactive substances (TBARS). Although methanol extracts reduce DPPH radicals more efficiently than ethyl ether extracts, suggesting a potent radical scavenger activity, the ethyl ether extracts were found to be most active in inhibiting lipid peroxidation in sarcoplasmic reticulum (SR) membranes. In addition, both extracts present peroxyl and superoxide radical scavenging activities. Peroxyl radicals were generated by the water soluble 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) azoinitiator, and the scavenging activities of the extracts were measured by the inhibition of cis-parinaric acid (PnA) fluorescence decay in SR. Superoxide radicals were generated either by an enzymatic or a non-enzymatic system, and the scavenger ability was evaluated by the inhibition of nitroblue tetrazolium reduction. Methanolic extracts are more potent as scavengers of peroxyl and superoxide radicals than the ethyl ether extracts. Apparently, there is a relationship between antioxidant potency and the total phenolic groups content in each extract.
805 citations
TL;DR: Data indicate that phenolic compounds (stilbenes, catechins, anthocyanins) exhibit interesting properties which may account in part for the so-called "French paradox," i.e. that moderate drinking of red wine over a long period of time can protect against coronary heart disease.
448 citations
TL;DR: Antioxidant activity was detected in some components of both the active and placebo mixtures, but the formulated active mixture was significantly more effective than the formulated placebo mixture.
320 citations
TL;DR: In this article, the antioxidant activity of aqueous extracts of rooibos tea (unfermented, semi-fermented and fermented) was compared with that of green, oolong and black teas.
285 citations
TL;DR: In this paper, the antioxidant effect of seaweed extracts was evaluated by determination of lipoxygenase activity and by α, α-diphenyl-β-picrylhydrazyl (DPPH) decolorization.
Abstract: The inhibition of lipid peroxidation and radical scavenging effects were studied to evaluate the antioxidant activity for extracts of 17 species of seaweed The antioxidant effect was evaluated by determination of lipoxygenase activity and by α, α-diphenyl-β-picrylhydrazyl (DPPH) decolorization Lipoxygenase activity was depressed in the presence of aqueous and ethanol extracts of 4 algal species; Sargassum species had the highest antioxidant activity of all the species examined The ethanol extracts of one Sargassum species showed competitive inhibition with the substrate The same species also showed radical scavenging activity in the DPPH decolorization test Comparison of these results shows no relationship between enzyme inhibition and radical scavenging activity
273 citations
TL;DR: The results indicated that the dried flower extracts of H. sabdariffa L. protect rat hepatocytes from t-BHP-induced cytotoxicity and genotoxicity by different mechanisms.
247 citations
01 Dec 1997
TL;DR: The in vitro antioxidant potential of Triphala and its constituents was tested with the following systems: radical scavenging activity measured by DPPH reduction, and superoxide radical and peroxy...
Abstract: The in vitro antioxidant potential of Triphala and its constituents was tested with the following systems: radical scavenging activity measured by DPPH reduction, and superoxide radical and peroxy ...
235 citations
TL;DR: Results clearly indicate that N,N‐DEAEFo are acting as promising antioxidants and radioprotectors comparable to rutin activities: they should prove to be useful under acute oxidative stress conditions for which both properties were required.
Abstract: The antiradical and antioxidant activities of four biologically active N,N-diethyloaminoethyl ethers of flavanone oximes (N,N-DEAEFo) were investigated in vitro and compared with these of polyphenolic flavonoid (rutin). Four experimental models were used: iron- and ascorbate driven Fenton systems, gamma-radiolysis, xanthine/xanthine oxidase system and diphenylpicrylhydrazyl (DPPH) radical scavenging. The results clearly indicate that N,N-DEAEFo are acting as promising antioxidants and radioprotectors comparable to rutin activities: they should prove to be useful under acute oxidative stress conditions for which both properties were required.
113 citations
TL;DR: The solution spectra revealed a broader spectrum with ments performed in a rapidly swept magnetic field generated a characteristic quintet due to the partly resolved hyperfine by pulsed magnets, and the problem of DPPH lineshape and intensity.
92 citations
TL;DR: The free radical scavenging activity guided fractionation and chemical analysis led to the isolation of a new compound, propol {3-[4-hydroxy-3-(3-oxo-but-1-enyl)-phenyl]-acrylic acid, which was more potent than most common antioxidants such as vitamin C and vitamin E in these assay systems.
Abstract: We evaluated free radical scavenging activity of the water, methanol and chloroform extracts of propolis in 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and xanthine-xanthine oxidase (XOD) generated superoxide anion assay systems. The free radical scavenging activity guided fractionation and chemical analysis led to the isolation of a new compound, propol (3-[4-hydroxy-3-(3-oxo-but-1-enyl)-phenyl]-acrylic acid) from the water extract, which was more potent than most common antioxidants such as vitamin C and vitamin E (alpha-tocopherol) in these assay systems.
TL;DR: The induction of in vivo antioxidant potential following small doses of gamma-ray irradiation was investigated in C57BL/6 mice in terms of the scavenging activity of cytosol fractions against 1,1-diphenyl-2-picrylhydrazyl (DPPH), a chemically stable radical.
Abstract: The induction of in vivo antioxidant potential following small doses of gamma-ray irradiation was investigated in C57BL/6 mice. The antioxidant capacity of various organs was assessed in terms of the scavenging activity of cytosol fractions against 1,1-diphenyl-2-picrylhydrazyl (DPPH), a chemically stable radical. Significant elevations in the scavenging activity were recognized in several organs, including the liver, pancreas and brain, soon after post-irradiation with 50 cGy of gamma-ray. These increases persisted for 24 h. gamma-Radiation of the liver at 25-50 cGy elevated its cytosolic antioxidant capacity, but this was lowered at 200 cGy. In order to assess which antioxidants underlie this phenomenon, the content of a reduced form of glutathione (GSH) in liver was assayed as a function of time after gamma-irradiation at a dose of 50 cGy. The GSH content was significantly increased from 6 h after irradiation, and this change was consistent with that of the total radical scavenging potency of the liver against DPPH. Further, the elevation of GSH content was accompanied by elevated GSSG reductase activity induced by gamma-irradiation.
TL;DR: From results, banaba extract was demonstrated to be useful as an antioxidant or free radical scavenger to protect biological systems against oxidative stress.
Abstract: In order to develop naturally occurring antioxidants from edible plants, the antioxidative effect of hot water extracts of Lagerstroemia speciosa leaves, known by the Tagalog name of banaba in the Phillipines, was studied. The content of tannin in banaba extract was 36.8% in dry weight. Banaba extract showed strong antioxidative activity in a linoleic acid autoxidation system. Banaba extract was found to have a potent radical scavenging action on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and superoxide radicals (O2− ) generated by a hypoxanthine (HPX)/xanthine oxidase (XOD) system. In vitro lipid peroxidation of rat liver homogenate induced by tert-butyl hydroperoxide (BHP) was inhibited by the addition of banaba extract in a dose-dependent manner. From these results, banaba extract was demonstrated to be useful as an antioxidant or free radical scavenger to protect biological systems against oxidative stress.
TL;DR: The radical scavenging effect of compounds 1 and 2 on DPPH radical exceeded that of L-ascorbic acid which is a well known antioxidant and these two compounds also showed prominent inhibitory activity against free radical generation in dichlorofluorescein (DCF) method and cytoprotective effect againstt-BHP in cultured liver cell.
Abstract: A strong antioxidant activity, which was measured by the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical, was detected in the methanol extract ofSalvia miltiorrhiza Bunge (Labiatae). By activity-directed fractionation, compounds 1 and 2 were isolated as antioxidant principles ofS. miltiorrhiza. Compounds 1 and 2 were identified as dimethyl lithospermate and 3-(3,4-dihydroxyphenyl)lactamide, respectively, on the basis of spectral data. The radical scavenging effect of compounds 1 and 2 on DPPH radical exceeded that of L-ascorbic acid which is a well known antioxidant. These two compounds also showed prominent inhibitory activity against free radical generation in dichlorofluorescein (DCF) method and cytoprotective effect againstt-BHP in cultured liver cell.
TL;DR: The antioxidant activity of Artemisia iwayomogi was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, which was comparable to that of L-ascorbic acid, which is a well known antioxidant.
Abstract: The antioxidant activity ofArtemisia iwayomogi was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The methanol extract ofA. iwayomogi showed strong antioxidant activity, and thus fractionated with several solvents. The antioxidant activity potential of the individual fraction was in the order of ethyl acetate>n-butanol>water>chloroform>n-hexane fraction. The ethyl acetate andn-butanol soluble fractions exhibiting strong antioxidant activity were further purified by repeated silica gel and Sephadex LH-20 column chromatography. Antioxidant chlorogenic acid was isolated as one of the active principles from then-butanol fraction, together with the inactive components, 1-octacosanol, scopoletin, scopolin, apigenin 7,4'-di-O-methylether luteolin 6,3'-di-O-methylether (jaceosidin), apigenin 7-methylether (genkwanin), 2,4-dihydroxy-6-methoxyacetophenone 4-O-beta-D-glucopyranoside and quebrachitol. The antioxidant activity of chlorogenic acid was comparable to that of L-ascorbic acid, which is a well known antioxidant.
TL;DR: In this paper, a first simultaneous EPR- and VIS-spectrophotometric study is reported on the interaction of the stable free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH) dissolved in ethanol with thioglycolic acid (HSCH2CO2H, TGA).
Abstract: A first simultaneous EPR- and VIS-spectrophotometric study is reported on the interaction of the stable free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH) dissolved in ethanol with thioglycolic acid (HSCH2CO2H, TGA). The results of the kinetic studies at room temperature permit to assume 1:1 stoichiometry of the reaction between DPPH and TGA giving 1,1-diphenyl-2-picryl-hydrazine (DPPH2) and thioglycolic disulphide. The linear plots of EPR- and UV/Vis responses vs. the quantity of added TGA are used to find the DPPH molar absorptivity at 520 nm to be 12350 ± 3% l · mol–1· cm–1 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 give results suggesting that in the solid state DPPH is a fairly stable material.
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TL;DR: In this paper, the various extracts from RVS (Rhus Verniciflua Stokes) were tried out with either DPPH or thiocyanate method.
Abstract: To measure antioxidative activities, the various extracts from RVS (Rhus Verniciflua Stokes) were tried out with either DPPH or thiocyanate method. Also we used the GO (Glucose Oxidase) 20 mU/mL hydroxyl radical system in mouse whole brain cell culture. Chloroform, n-hexane or ethanol were used as extract solutions which had different polarity respectively. In DPPH and thiocyanate method, the antioxidative activities of the crude ethanol extracts were stronger than other extracts. The crude ethanol extracts were fractionated 5 peaks by glass column. Among of them, antioxidative activity of peak II was shown stronger than other fractions, a little for peak III and peak IV , and none for peak I and Peak V . In the antioxidative effects of crude ethanol extracts (30 mg/mL), cell viabilities were evaluated , of crude ethanol extracts 59%, 68% respectively. addition of crude ethanol extracts had 95% cell viabilities, 0.01% significant, comparing control. In addition, the compounds related to antioxidative effect of crude ethanol extract might be glycoproteins by means of SDS-PAGE. Comparison to antioxidative effects between several antioxidants (ascorbic acid, , catalase) addition of crude ethanol extracts corresponds to catalase in antioxidative effects.
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TL;DR: Both anti-inflammatory and antioxidant activities depended on some structural characteristics of the synthesized compounds, and it was attempted to correlate the above mentioned activities with some physicochemical parameters using a quantitative structure-activity relationship approach.
Abstract: Six substituted oxo- or hydroxy-aminoethanols and ethylenediamines were synthesized and tested as anti-inflammatory agents. 1-Substituted 4-(2-aminoethylamino)-1-butanones and 1-substituted 4-(2-hydroxy-ethylamino)-1-butanones were prepared by reacting the appropriate 4-chloro-1-butanone with the corresponding aminoalcohol or ethylenediamine. I-Substituted 4-(2-aminoethylamino)-l-butanols were prepared by the reduction of the ketones with NaBH 4 or NaBH 3 CN. The R M values of the synthesized compounds were determined as an expression of their lipophilicity. The effect of these compounds on in vitro non-enzymatic lipid peroxidation, their hydroxyl radical scavenging activity and their ability to interact with 1,1-diphenyl-2-picrylhydrazyl stable free radical (DPPH) were studied. The effect of the synthesized compounds on inflammation, using the carrageenan induced rat paw edema model was studied. Both anti-inflammatory and antioxidant activities depended on some structural characteristics of the synthesized compounds. It was also attempted to correlate the above mentioned activities with some physicochemical parameters using a quantitative structure-activity relationship approach. The primary amino group appeared to be of importance for antioxidant activity in this series of compounds.
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TL;DR: In this paper, the interaction between poly(N,N-dimethylaniline) (PDMA) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) was investigated by ESR spectra based on the stability of their radicals in ethanol.
Abstract: Electron spin resonance (ESR) is a sensitive tool to detect the electron-transfer processes in some specified systems from the change of the ESR signals. In this paper, the interaction between poly(N,N-dimethylaniline) (PDMA) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) was investigated by ESR spectra based on the stability of their radicals in ethanol. It is shown that an electron-transfer process occurs from nitrogen atoms of PDMA molecules to those of DPPH molecules which makes PDMA form more stable radical cations and eliminates the radicals on DPPH.
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TL;DR: Some modified novel thiazol-5yl-aminoketones were evaluated for their anti-inflammatory, analgesic and antiproteolytic activities and their activity is related to certain structural characteristics.
Abstract: Some modified novel thiazol-5yl-aminoketones were evaluated for their anti-inflammatory, analgesic and antiproteolytic activities. Their inhibitory activity on 12-lipoxygenase (12-LO) and beta-glucuronidase in vitro was estimated. Their interaction with the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and their RM values were also determined. For two of them, the effect on zoxazolamine-induced paralysis after a prolonged treatment was determined. The duration of paralysis for the same compounds, (only one administration, one before zoxazolamine injection) was recorded too. The 2-amino substituted derivatives seem to be more potent in comparison with the 2-phenyl. The tested compounds were found to influence proteolysis but not the activities at beta-glucuronidase and 12-LO. Their interaction with DPPH was mild. Compound 2 seems to modify the activity of the hepatic drug metabolizing enzymes. In conclusion, their activity is related to certain structural characteristics.
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TL;DR: One flavan 3-ol derivative was isolated from the stem of Acer mono Max, along with two known coumarins as mentioned in this paper, and the structures of these compounds were established as (-) - epicatechin, scopoletin, and isoscopolettin.
Abstract: One flavan 3-ol derivative was isolated from the stem of Acer mono Max, along with two known coumarins. On the basis of spectroscopic evidence, the structures of these compounds were established as (-) - epicatechin, scopoletin and isoscopoletin. Antioxidative activity of (-) - epicatechin was examined by the DPPH free radical scavenging method. Antioxidative activity of (-) - epicatechin was more greater than those of and .
TL;DR: In this paper, the ESR of DPPH decorated polycrystalline CuO in the temperature range 77-300 K was reported, and the line width and intensity changes observed suggest that the probe is sensing the susceptibility changes through magnetic phase transitions at 229 and 213 K.
Abstract: We report on the ESR of DPPH decorated polycrystalline CuO in the temperature range 77–300 K. Line width and intensity changes observed suggest that the DPPH probe is sensing the susceptibility changes through magnetic phase transitions at 229 and 213 K.
01 Jan 1997
TL;DR: In this paper, the authors showed that AOB-treated rats also scavenged Superoxide and diphenyl-p-picrylhydrazyl (DPPH) radicals, and Fenton's reaction and lipid peroxidation are also inhibited by AOB.
Abstract: Antioxidant biofactor (AOB®) is an unique processed grain food obtained from soybean, wheat, rice germ, rice bran, tear grass, green tea, sesame, citron, green leaves extracts and malted rice. These ingredients were degraded to low molecular weight compounds by roast and fermentation with Aspergilus oryzae (Fig. 1). AOB contains a variety of compounds with antioxidant activity including flavonoids, α-tocopherol, vitamin C, tannins and vitamin B2. These ingredients have potent activity to scavenge reactive oxygen species, such as Superoxide radical dose-dependently. Plasma of AOB-treated rats also scavenge Superoxide and diphenyl-p-picrylhydrazyl (DPPH) radicals1). Fenton’s reaction and lipid peroxidation are also inhibited by AOB1). Thus, AOB is a potent antioxidant both in vitro and in vivo. The present work demonstrates its effect on ischemia/reperfusion-induced renal injury and the fate of NO in the rat.
30 Jun 1997
TL;DR: In this paper, a spectrophotometric method was developed for the determination of some cephalosporins using 2,2'-diphenyl-1-picrylhydrazyl (DPPH), the latter employed to abstract a hydrogen atom from the drug thereby promoting a process of radical coupling.
Abstract: A spectrophotometric method was developed for the determination of some cephalosporins using 2,2'-diphenyl-1-picrylhydrazyl (DPPH). The latter employed to abstract a hydrogen atom from the drug thereby promoting a process of radical coupling. This results in a reduction of the violet color (520 nm) of DPPH with the formation of the yellow colored 2,2'-diphenyl-1-picrylhydrazine (DPPH). This fading in color of DPPH reagent depends on the concentration of the drug being determined. Beer's law was obeyed in the ranges of; 5-30, 5-25 and 10-30 µg/ml for cephalexin, cefadroxil and cephradine respectively. The validity of the method was tested by carrying out standard addition procedure analyzing the studied drugs in pure form as well as in their pharmaceutical preparations without interference from common additives. The percentage recovery ranged from (97.98-101.21) ±1.15-0.98.