be incriminated as an explanation for increased uri- nary o -tyrosine, one would have anticipated in- creased urinary phenylalanine losses. This was not found, thus making preferential urinary o -tyrosine losses within the group of infants receiving supple- mental oxygen unlikely. Similarly, the frequent oc- curence of patent ductus arteriosus within the group of infants on supplemental oxygen is probably not the direct result of pathophysiologic processes asso- ciated with increased oxygen free radicals. In con- trast, hydroxylradical attack may well be the pri- mary mechanism of injury responsible for chronic complications such as bronchopulmonary dysplasia experienced by infants receiving long-term oxygen treatment.
hydroxylradical ( . OH) in slurries of oxygenated water. Understanding the formation and fate of these reactive oxygen species is important to biological and ecological systems as exposure can lead to deleterious health effects, but also environmental engineering during the optimization of remediation approaches for possible treatment of contaminated waste streams. This study presents the use of the amino acid phenylalanine (Phe) to monitor the kinetics of pyrite-induced . OH formation through rates of hydroxylation forming three isomers of tyrosine (Tyr) - ortho-, meta-, and para-Tyr. Results indicate that about 50% of the Phe loss results in Tyr formation, and that these products further react with . OH at rates comparable to Phe. The overall loss of Phe appeared to be pseudo first- order in [Phe] as a function of time, but for the first time it is shown that initial rates were much less than first- order as a function of initial substrate concentration, [Phe] o . These results can be rationalized by considering that
With 750 nm excitation this shows a fifth-order power dependence resulting from combined 2-photon excitation of the photoproduct that is itself produced in a three- photon event. This green luminescence is also produced during multiphoton irradiation of aqueous solutions of tryptophan at very high peak laser powers, suggested to result from dielectric breakdown and hydroxylradical formation from water and subsequent hydroxylation of tryptophan to 5HTrp (10). We have used this green luminescence as a marker for hydroxylradical formation from 2-photon excitation of the “photoFenton” reagent N-hydroxypyridine-2-thione
A number of highly reactive oxygen species have been implicated in the oxygen-dependent mechanisms involved in bactericidal activity of phagocytic leukocytes. Hydrogen peroxide and superoxide, two agents known to occur during phagocytosis, are thought to interact to generate hydroxylradical, singlet oxygen, and other potentially reactive molecules. Using an assay system of ethylene generation from methional, cell preparations of human monocytes were demonstrated to generate hydroxylradical or a similar agent during phagocytosis of zymosan particles. The generation of ethylene was impaired by agents which reduce superoxide or hydrogen peroxide concentrations as well as by agents reported to be hydroxylradical scavengers. The ethylene generation did not appear to be dependent on myeloperoxidase in that azide enhanced ethylene generation. Monocytes from a patient with chronic granulomatous disease failed to generate ethylene during phagocytosis. This assay technique may be useful in exploring the metabolic events integral to the bactericidal and inflammatory activity of phagocytic leukocytes.
oxidizing agent. When neutrophils were exposed to opsonized zymosan in the presence of 0.35 mM methional, ethylene was released in quantities amounting to 44.6+/-3.6 pmol/10(6) cells/40 min. Ethylene production required the presence of neutrophils, opsonized zymosan, and methional, indicating that it was formed from methional by stimulated but not resting neutrophils. Ethylene was not produced by zymosan-treated cells from patients with chronic granulomatous disease, confirming the requirement for respiratory burst activity in this process. Ethylene production was suppressed by benzoic acid, an OH- scavenger. Superoxide dismutase (3 microgram/ml) reduced ethylene production to 21% of control levels, but catalase had no significant effect in this system. These findings indicate that stimulated neutrophils produce a highly reactive oxidizing radical, possibly OH-, which releases ethylene from methional, and that the O2-generated during the respiratory burst is involved in the production of this reactive species.
radical absorbance capacity (ORAC). Peroxyl and hydroxylradical generators were used in the analysis. All ORAC analysis were carried out on the Perkin-Elmer spectroﬂ uorometer LS with ﬂ uorescent ﬁ l- ters, Ex: nm; Em: nm. Final results were calculated using the diﬀ erences between area under the quenching curve of ﬂ uorescein (FL), blank and analyzed biological samples. AC against peroxyl radicals (ORAC- ROO °) of lipophilic fraction in MC of AD was statistically signiﬁ cantly lower in comparison with
Concerning antioxidant activity by the reducing ability of a compound generally depends on the presence of reductones, which exert antioxidant activity by breaking free radical chain culminating in donating a hydrogen atom.  The antioxidant principle present in the fraction extracts of O. celtidifolia caused the reduction of Fe 3+ / ferricyanide complex to the ferrous form, and thus proved the reducing ability.  The hydroxylradical scavenging activity of leaves fraction was effectual than other fractions. Hydrogen peroxide itself is not particularly reactive with most biologically important molecules, but it is an intracellular precursor of hydroxyl radicals which is very toxic to the cell.  The leaves fraction extract scavenged hydrogen peroxide, which may be attributed to the presence of phenolic group that donate electrons to hydrogen peroxide there by neutralizing it into water, as opined by.  The antioxidant activity by phosphomolybdenum method exhibited higher antioxidant activity of leaves fraction in comparison with other fractions.
The reducing power of the whole plant extract was quantified according to the method of Oyaizu  . DPPH radical scavenging activity was adopted from those previously described with slight modifications  . The total antioxidant potential of sample was determined using Ferric Reducing Ability of Plasma (FRAP) by method of Benzie and strain (1996). FRAP assay measures the change in absorbance at 593 nm owing to the formation of a blue coloured Fe 2+ - TPTZ compound from colourless oxidized Fe 3+ form by the action of electron donating antioxidants. The hydroxylradical scavenging activity was measured according to the method Klein et al  .
Superoxide anion plays an important role in the formation of more reactive species such as hydrogen peroxide, hydroxylradical and singlet oxygen, which induce oxidative damage in lipids, proteins, and DNA . Therefore, studying the scavenging activity of plant extracts on superoxide radical is one of the most important ways of clarifying the mechanism of antioxidant activity.
In the present study, the antioxidant activity of methanol extract of Indigofera linnaei (MEIL) was evaluated by different in vitro antioxidant assay models. The total phenol and flavonoid content was also determined in the extract. MEIL exhibited strong antioxidant and scavenging activity on ABTS radical cation, DPPH free radical, hydrogen peroxide, nitric oxide, superoxide radical and hydroxylradical. The extract showed strong activity in Iron reducing power assay. The antioxidant and free radical scavenging activities of the extract were comparable to standard antioxidants used such as ascorbic acid and rutin. The extract had good phenol and flavonoid contents. The antioxidant activity may be due to the rich amount of phenols and flavonoids present in the extract. Therefore, the plant could be considered as a very good antioxidant source with therapeutic potential.
Antioxidants are an inhibitor of the process of oxidation, even at relatively small concentration and thus have diverse physiological role in the body. Natural antioxidants are constituents of many fruits and vegetables and they have attracted a great deal of public and scientific attention. Natural antioxidants occur in all parts of plants. In the present study to investigate the antioxidant potential of Aplotaxis auriculata rhizome extract. The Aplotaxis auriculata extract was screened for in vitro antioxidant activity by nitric oxide radical scavenging, oxygen radical scavenging such as DPPH scavenging, superoxide anion radical scavenging, total antioxidant, hydroxylradical, nitric oxide scavenging and metal chelation activity at different concentrations. Throughout the studies extract showed marked antioxidant activity. The antioxidant activity of the extract may be due to the phytochemicals present in it. The antioxidant activity was found to be concentration dependent and may be attributed to the presence of bioflavonoids content in the of Aplotaxis auriculata. Overall, the plant extract is a source of natural antioxidants which might be helpful in preventing the progress of various oxidative stress mediated diseases including aging.
The purpose of this study was to elucidate the antioxidant capacities of Tricholoma giganteum. Three fractions from the mushroom were evaluated for antioxidant activity against hydroxylradical, superoxide radical, DPPH radical, ferrous ion chelating ability and reducing power. Among three different fraction (Fa, Fb and Fc), the fraction Fa had a strong antioxidant activity and Fc also presented a relatively strong antioxidant effect. Whereas, the polysaccharide fraction Fb was found to be a weak scavenger of free radicals when compared to Fa and Fc. Cellular damage caused by reactive oxygen species has been implicated in several diseases and hence antioxidants have significant importance in human health. Our result thus indicates that Fa fraction of T. giganteum has maximum antioxidant property and may be utilized as a promising source of therapeutics.
antioxidant activity of leaf extract of R. apetalus. Extraction of powdered leaf material was carried out by maceration process using water. Preliminary phytochemical analysis was carried out by standard tests. In vitro antioxidant activity was evaluated by four vitro assays viz. DPPH scavenging, ABTS scavenging, hydroxylradical scavenging and lipid peroxidation inhibition assays. Total phenolic and flavonoid contents were estimated. Phytochemical analysis of leaf extract revealed the presence of saponins, alkaloids, flavonoids, phenolics, tannins, phytosterols and triterpenoids. Leaf extract was found to scavenge DPPH, ABTS and hydroxyl radicals dose dependently with IC 50 value of 22.49, 17.52 and 33.43µg/ml respectively. Inhibition of lipid peroxidation by leaf
A study was conducted to assess the antioxidant activity of medicinal rice (Oryza Sativa L.) cv. Njavara and the results revealed that among the three rice varieties selected NY had the highest DPPH activity and hydroxylradical scavenging activity with an with an IC 50 value of 31.62 µg/ml. and 46
The bioactive fraction (aqueous fraction) was tested for the anti-oxidant activity. Different in vitro methods such as DPPH free radical scavenging assay, nitric oxide radical scavenging assay, superoxide radical scavenging assay, hydroxylradical scavenging assay and inhibition of peroxide formation method, was carried out. The percentage inhibition of free radicals produced was found by spectrophotometric method and the values are represented as mean±SD. The absorbance obtained for test and control are noted and the percentage inhibition of radical scavenging activity was calculated using the equation,
was generated by mixing 300 mM sodium acetate buffer (pH 3.6), 10.0 mM (tripyridyl triazine) tripyridyltriazine (TPTZ) solution, and 20.0 mM ferric chloride (FeCl 3 ).6H 2 O solution in a ratio of 10:1:1 in volume. Samples at different concentrations (100, 200, 300, 400, and 500 µg/ml) were then added to 3 ml of FRAP reagent, and the reaction mixture was incubated at 37°C for 30 min. The increase in absorbance at 593 nm was measured. Fresh working solutions of ferrous sulfate (FeSO 4 ) were used for calibration. The antioxidant capacity based on the ability to reduce ferric ions of the sample was calculated from the linear calibration curve and expressed as mmol FeSO 4 equivalents per gram of sample. Hydroxylradical scavenging activity
essential oils from both the plant species reveals its potency as natural free radical scavengers. The minimum and maximum values of inhibition ranged from 39.4 to 89.3% for the oil from P. benghalensis and 37.3 to 86.7% for P. cablin. Reducing power of Eos from P. benghalensis and P. cablin were described in Table 2 & 4. The reducing power of the Eos increased with concentration. The reducing power of both species showed excellent result in comparison with synthetic antioxidants. The values ranged from 31.7 -78.6% and 28.6-72.3% for P. benghalensis and P. cablin respectively. The reducing power of ascorbic acid and BHT were 78.7 and 72.5% respectively. From the analysis it was noticed that in hydroxylradical scavenging activity, percentage of inhibition increased with concentration. The activity was tested with concentration ranging from 20-100 µg/ml. Highest values of 85.9 and 88.4% were observed at concentration 100 µg/ml for P. benghalensis and P. cablin respectively. It is interesting to note that a positive correlation with the concentration and the volatile compounds present in the Eos results in the active radical scavenging capacity.
One of merits of the present multi-gas dielectric barrier discharge is the com- parison of the discharge characteristics in air and pure oxygen. Various reactive species are generated in the discharge region and the inhibition of the produc- tion of ozone. In the experiment, DNP with the different position of nitro group is examined using 2,4-DNP, 2,5-DNP and 3,4-DNP (Appendix). Using the mo- lecular orbital theory, LUMO and HOMO energy of the starting system and the produced system were calculated considering hydroxylradical and excited hy- droxyl anion as active agents.
Hydroxylradical scavenging activity: Hydroxylradical scavenging activity was assayed using salicylic method . Hydroxylradical was formed by Fenton reaction. Different polysaccharide solutions (0.2mL) at various concentrations were mixed with 1 mL 2 mM FeSO 4 ， 0.4 mL 2 mM sodium salicylic and 1 mL 1 mM H 2 O 2 . Then the mixture was kept in water bath at 37 ℃ for 1 h. The absorbance of resulting solution was measured at 510 nm. Ascorbic acid (Vc) was used as positive controls.
Four different honey samples, viz. Sundarban honey, Litchi honey, Cumin honey and Eucalyptus honey, produced in the Southern part of West Bengal (India), were tested for their antioxidant and antimicrobial properties. Among the six standard antioxidant assay protocols (viz. ABTS radical decolorization assay, DPPH radical decolorization assay, assay for total phenolis content, FRAP assay, hydroxylradical scavenging assay and assay for inhibition of lipid peroxidation) applied in the present study, Sundarban honey gave the best result, in terms of gallic acid equivalents. Greater antioxidant potential of the sample was reflected in its’ antibacterial property, as it produced highest zone of inhibition against all the five bacteria (viz. Escherichia coli, Klebsiella aerogens, Staphylococcus aureus, Salmonella typhi and Bacillus cereus) used in the study. Eucalyptus honey was the second best in the study protocols. The honey samples possessed very low hydroxylradical scavenging or anti-lipid peroxidation activities, indicating that the samples might produce peroxide themselves for their antibacterial activities.