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Free-radical Scavengers (free-radical + scavenger)

Distribution by Scientific Domains

Medical Sciences	50%
Chemistry	50%

Selected Abstracts

Dolichandroside A, a new , -glucosidase inhibitor and DPPH free-radical Scavenger from Dolichandrone falcata seem

PHYTOTHERAPY RESEARCH, Issue 4 2009
P. Aparna
Abstract A new phenylpropanoid glycoside, dolichandroside-A, together with seven known compounds , -lapachone, lapachol, aloesaponarin II, 8-hydroxydehydroiso- , -lapachone, , -sitosterol, 3,8-dihydroxydehydroiso- , -lapachone and verbascoside were isolated from the active ethyl acetate soluble extract of heartwood of Dolichandrone falcata. All except for dolichandroside-A are known compounds, but have been isolated for the first time from this plant. The structure of all these compounds was determined on the basis of 1D- and 2D-NMR spectral data. All the isolates were tested for , -glucosidase inhibitory and DPPH radical scavenging activity. This is the first report identifying DPPH scavenging activity and , -glucosidase inhibitory activity in D. falcata. Furthermore, along with a new compound, dolichandroside-A, this study also assigns for the first time , -glucosidase inhibitory activity to verbascoside and aloe saponarin-II. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Effects of edaravone on human neutrophil function

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2005
K. Mikawa
Background:, Neutrophils play a crucial role in the antibacterial host defence system. Edaravone is used in critically ill patients who are often immuno-compromised secondary to concomitant disease or immunosuppressive therapy. The aim of the current study was to assess the effect of edaravone, a novel free-radical scavenger, on several aspects of human neutrophil function using an in vitro system. Methods:, Chemotaxis, phagocytosis, reactive oxygen species (ROS) production by neutrophil (cellular) and xanthine-xanthine oxidase (acellular) systems, and intracellular calcium ion levels ([Ca2 + ]i) were measured in the absence and in the presence (at a clinically relevant concentration, and 0.1-fold, and 10-fold this concentration) of edaravone. Results:, The clinically relevant concentration of edaravone did not inhibit chemotxais, phagocytosis, or superoxide production of neutrophils. Even at its ordinary clinical plasma concentration, the drug inhibited hydrogen peroxide (H2O2) and hydroxyl radical (OH·) generation in the cellular (neutrophil) as well as in the cell-free (xanthine-xanthine oxidase) system (P < 0.05). Edaravone did not affect elevation of [Ca2 + ]i in neutrophils stimulated by a chemotactic factor. Conclusions:, These findings suggest that edaravone quenched H2O2, and OH· generated rather than impaired the ability of neutrophils to produce the ROS. However, further studies using in vivo systems are required to elucidate the effects of edaravone on neutrophil function in clinical settings. [source]

Formation and decay of the ABTS derived radical cation: A comparison of different preparation procedures

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2002
Carola Henriquez
Bleaching of a preformed solution of the blue-green radical cation 2,2,-azinobis (3-ethylbenzothizoline-6-sulfonic acid) (ABTS+·) has been extensively used to evaluate the antioxidant capacity of complex mixtures and individual compounds. The reaction of the preformed radical with free-radical scavengers can be easily monitored by following the decay of the sample absorbance at 734 nm. The ABTS radical cation can be prepared employing different oxidants. Results obtained using MnO2 as oxidant show that the presence of manganese ions increases the rate of [ABTS]+· autobleaching in a concentration-dependent manner. The radicals can also be obtained by oxidizing ABTS with 2,2, -azobis(2-amidinopropane)hydrochloride (AAPH) or peroxodisulfate (PDS). The oxidation by AAPH takes place with a large activation energy and a low reaction order in ABTS. The data support a mechanism in which the homolysis of AAPH is the rate-limiting step, followed by the reaction of ABTS with the peroxyl radicals produced after the azocompound thermolysis. On the other hand, the low activation energy measured employing PDS, as well as the kinetic law, are compatible with the occurrence of a bimolecular reaction between the oxidant and ABTS. Regarding the use of ABTS-based methodologies for the evaluation of free radical scavengers, radical cations obtained employing AAPH as oxidant can be used only at low temperatures, conditions where further decomposition of the remaining AAPH is minimized. The best results are obtained with ABTS derived radicals generated in the reaction of PDS with an ABTS/PDS concentration ratio equal (or higher) to two. However, even with radicals prepared by this procedure, stoichiometric coefficients considerably larger than two are obtained for the consumption of the radical cation employing tryptophane or p -terbutylphenol as reductants. This casts doubts on the use of ABTS-based procedures for the estimation of antioxidant capacities. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 659,665, 2002 [source]

Polyphenols from Polygala spp. and Their Antioxidant Activity

CHEMISTRY & BIODIVERSITY, Issue 3 2004
Rinaldo Cervellati
Members of Polygalaceae are known to contain a variety of different polyphenolic compounds such as xanthones, flavonoids, and biphenyl derivatives. Here, we report the isolation and structural characterization of two new phenol derivatives, named alpestrin (=3,3,,5,-trimethoxy[1,1,-biphenyl]-4-ol; 10) and alpestriose,A (=6- O -benzoyl-1- O -{6- O -acetyl-3- O -[(4-hydroxy-3,5-dimethoxyphenyl)prop-2-enoyl]- , - D -fructofuranosyl}- , - D -glucopyranoside; 11), and of four known compounds (12,15) from the MeOH extract of Polygala alpestris. The relative in vitro antioxidant activities of these compounds, in comparison with other phenolic substances from Polygala vulgaris, were evaluated by means of the BriggsRauscher (BR) oscillating reaction, a method based on the inhibitory effects of antioxidant free-radical scavengers. The experimental antioxidant-activity values (relative to resorcinol as a standard) were compared with those calculated on the basis of the bond-dissociation enthalpies. The structure/activity relationships for the compounds examined are also discussed. [source]