Hydroxyl and superoxide radical scavenging abilities of chromonyl‐thiazolidine‐2,4‐dione compounds

The oxygen free radical scavenging activities of 15 chromonyl‐thiazolidine‐2,4‐dione compounds (CTDs) were examined in chemical systems producing superoxide anion radicals, O (potasium superoxide–18‐crown‐6 ether–DMSO), and hydroxyl radicals, HO^? (a Fenton reaction: Fe(II)–H₂O₂–sodium trifluoroacetate, pH 6.15). Chemiluminescence and electron spin resonance (ESR) spectroscopy using 5,5‐dimethyl‐1‐pyrroline‐1‐oxide (DMPO) as spin trap were applied to evaluate antioxidant behaviour of CTDs towards the oxygen radicals. The results indicated that 11 of the 15 tested compounds showed a significant inhibitory effect on the chemiluminescence generated from the O‐generating system, ranging from 41 to 86%, and 13 CTDs quenched the ESR signal of the DMPO–OH spin adduct by 33–86%, at a concentration of 1 mmol L^?1. Our findings demonstrate that CTDs could be good free radical scavengers. Copyright © 2008 John Wiley & Sons, Ltd.     

Scavenging of superoxide anion radical and hydroxyl radical by novel thiazolyl‐thiazolidine‐2,4‐dione compounds

The antioxidant behavior of a series of new synthesized substituted thiazolyl‐thiazolidine‐2,4‐dione compounds (TZDs) was examined using chemiluminescence and electron paramagnetic resonance spin trapping techniques. 5,5‐Dimethyl‐1‐pyrroline‐N‐oxide (DMPO) was used as the spin trap. The reactivity of TZDs with superoxide anion radical (O) and hydroxyl radical (HO^?) was evaluated using potassium superoxide/18‐crown‐6 ether dissolved in dimethylsulfoxide, and the Fenton‐like reaction (Fe²⁺ + H₂O₂), respectively. The results showed that TZDs efficiently inhibited light emission from the O generating system at a concentration of 0.05–1 mmol L^?1 (5–94% reductions were found at 1 mmol L^?1 concentration). The TZD compounds showed inhibition of HO^?‐dependent DMPO–OH spin adduct formation from DMPO (the amplitude decrease ranged from 8 to 82% at 1 mmol L^?1 concentration). The findings showed that examined TZDs had effective activities as radical scavengers. Copyright © 2009 John Wiley & Sons, Ltd.     

Free radical scavenging abilities of flavonyl‐thiazolidine‐2,4‐dione compounds

Free radical scavenging activity of flavonyl‐thiazolidine‐2,4‐dione compounds has been evaluated using chemiluminescence, electron spin resonance spectroscopy with 5,5‐dimethyl‐1‐pyrroline‐1‐oxide as spin trap and DPPH (2,2′‐diphenyl‐1‐picrylhydrazyl) method. The examined compounds exhibited 28–50% scavenging superoxide anion radical ( ), 16.7–76.7% hydroxyl radical (HO^?) and 9–40% DPPH radical. Compounds containing carbonyl group in their structure can be considered as antioxidants with high relevance and great biological importance. Copyright © 2009 John Wiley & Sons, Ltd.     

Scavenging capacities of some thiazolyl thiazolidine‐2,4‐dione compounds on superoxide radical,hydroxyl radical,and DPPH radical

The scavenging effects of eighteen thiazolyl thiazolidine‐2,4‐dione compounds (TTCs) on superoxide radical , hydroxyl radical HO^?, and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH^?) radical were evaluated by the chemiluminescence technique, electron spin resonance spectrometry (ESR) and visible spectrophotometry, respectively. The examined compounds were shown to have 27–59% scavenging ability, 19–69% HO^? scavenging activity and 2–32% DPPH^? scavenging ability. This property of the tested compound seems to be important in the prevention of various diseases of free radicals etiology. Copyright © 2009 John Wiley & Sons, Ltd.     

Scavenging of hydroxyl radical by catecholamines

The direct effects of the four catecholamines (CATs), adrenaline (A), noradrenaline (NA), dopamine (D) and isoproterenol (I), on free radicals were investigated using the free radical 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?) and hydroxyl radial (HO^?). The CATs examined were found to inhibit the ESR signal intensity of DPPH^? in a dose‐dependent manner over the range 0.1–2.5 mmol/L in the following order: NA > A > I > D, with IC₅₀ = 0.30 ± 0.03 for noradrenaline and IC₅₀ = 0.86 ± 0.02 for dopamine. Hydroxyl radicals were produced using a Fenton reaction in the presence of the spin trap 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO), and ESR technique was applied to detect the CATs reactivity toward the radicals. The reaction rates constant (k_r) of CATs with HO^? were found to be in the order of 10⁹ L/mol/s, and the k_r value for noradrenaline was the highest (k_r = 8.4 × 10⁹ L/mol/s). The CATs examined exhibited also a strong decrease in the light emission (62–73% at 1 mmol/L concentration and 79–89% at 2 mmol/L concentration) from a Fenton‐like reaction. These reactions may be relevant to the biological action of these important polyphenolic compounds. Copyright © 2012 John Wiley & Sons, Ltd.     

6‐Methyl 3‐chromonyl 2,4‐thiazolidinedione/2,4‐imidazolidinedione/2‐thioxo‐imidazolidine‐4‐one compounds: novel scavengers of reactive oxygen species

The benefits of antioxidants on human health are usually ascribed to their potential ability to remove reactive oxygen species providing protection against oxidative stress. In this paper the free radicals scavenging activities of nine 6‐methyl 3‐chromonyl derivatives (CMs) were evaluated for the first time by the chemiluminescence, electron paramagnetic resonance, spin trapping and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?) methods. The total antioxidant capacity was also measured using a ferric‐ferrozine reagent. Compounds having a hydrogen atom at the N3‐position of the β‐ring were effective in quenching CL resulted from the KO₂/18‐crown‐6‐ether system (a source of superoxide anion radical, ) in a dose‐dependent manner over the range of 0.05–1 mmol/L [IC₅₀ ranged from 0.353 (0.04) to 0.668 (0.05) mmol/L]. The examined compounds exhibited a significant scavenging effect towards hydroxyl radicals (HO^? HO^?), produced by the Fenton reaction, and this ranged from 24.0% to 61.0%, at the concentration of 2.5 mmol/L. Furthermore, the compounds examined were also found to inhibit DPPH^? and this ranged from 51.9% to 97.4% at the same concentration. In addition, the use of the total antioxidant capacity assay confirmed that CM compounds are able to act as reductants. According to the present study, CM compounds showed effective in vitro free radical scavenging activity and may be considered as potential therapeutics to control diseases of oxidative stress‐related etiology. Copyright © 2013 John Wiley & Sons, Ltd.     

Superoxide anion radical scavenging property of catecholamines

The direct effect of the four catecholamines (adrenaline, noradrenaline, dopamine and isoproterenol) on superoxide anion radicals () was investigated. The reaction between 18‐crown‐6‐ether and potassium superoxide in dimethylsulfoxide was used as a source of . The reactivity of catecholamines with was examined using chemiluminescence, reduction of nitroblue tetrazolium and electron paramagnetic resonance spin‐trapping techniques. 5,5‐Dimethyl‐1‐pyrroline‐N‐oxide was included as the spin trap. The results showed that the four catecholamines were effective and efficient in inhibiting chemiluminescence accompanying the potassium superoxide/18‐crown‐6‐ether system in a dose‐dependent manner over the range 0.05–2 mm in the following order: adrenaline > noradrenaline > dopamine > isoproterenol, with, IC₅₀ = 0.15 ± 0.02 mm 0.21 ± 0.03 mm , 0.27 ± 0.03 mm and 0.50 ± 0.04 mm , respectively. The catecholamines examined also exhibited a strong scavenging effect towards when evaluated this property by the inhibition of nitroblue tetrazolium reduction (56–73% at 1 m concentration). A very similar capacity of scavenging was monitored in the 5,5‐dimethyl‐1‐pyrroline‐N‐oxide spin‐trapping assay. The results suggest that catecholamines tested may involve a direct effect on scavenging radicals. Copyright © 2013 John Wiley & Sons, Ltd.     

Singlet oxygen scavenging activity of tocopherol and plastochromanol in Arabidopsis thaliana: relevance to photooxidative stress

In the present study, singlet oxygen (¹O₂) scavenging activity of tocopherol and plastochromanol was examined in tocopherol cyclase‐deficient mutant (vte1) of Arabidopsis thaliana lacking both tocopherol and plastochromanol. It is demonstrated here that suppression of tocopherol and plastochromanol synthesis in chloroplasts isolated from vte1 Arabidopsis plants enhanced ¹O₂ formation under high light illumination as monitored by electron paramagnetic resonance spin‐trapping spectroscopy. The exposure of vte1 Arabidopsis plants to high light resulted in the formation of secondary lipid peroxidation product malondialdehyde as determined by high‐pressure liquid chromatography. Furthermore, it is shown here that the imaging of ultra‐weak photon emission known to reflect oxidation of lipids was unambiguously higher in vte1 Arabidopsis plants. Our results indicate that tocopherol and plastochromanol act as efficient ¹O₂ scavengers and protect effectively lipids against photooxidative damage in Arabidopsis plants.     

Evaluation of the antioxidant activity of tetracycline antibiotics in vitro

Tetracyclines are the second most common antibiotic family in medicine usage. These antibiotics exhibit antioxidant potential; however, the exact mechanism remains unclear. The antiradical activity of the seven tetracyclines (TCs; tetracycline, chlortetracycline, oxytetracycline, doxocycline, methacycline, demeclocycline, minocycline) was determined using the free radical 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?) and hydroxyl radicals (HO^?) generated in a Fenton reaction. Electron spin resonance (ESR), ESR spin‐trapping, chemiluminescence and spectrophotometry techniques were applied. It was found that the TCs showed high DPPH antiradical activity in the range 26–96% at 2.5 mmol/L concentration. The second‐order rate constants for the reaction between HO^? and TCs were calculated, in the range (3.6–9.6) × 10⁹ L/mol/s. The tetracycline compounds also exhibited a strong decrease in light emission (range 61–85% at concentration of 1 mmol/L). This study also showed that TCs promote the generation of singlet oxygen in the presence of and Fe(II)/Fe(III) ions. Our findings suggest direct scavenging activity of the examined tetracyclines towards free radicals, and may be relevant to therapeutic strategy. Copyright © 2011 John Wiley & Sons, Ltd.     

Spin Trapping of Free Radicals Formed During Peroxidation of Sarcolemmal Membranes (SLM)

The generation of free radicals in a superoxide (O₂-)driven Fe⁺³ catalysed reactions with isolated myocytic sarcolemma using electron spin resonance was investigated. Incubation of highly purified canine myocytic sarcolemma in the presence of the spin trap, 2-methyl-2-nitrosopropane (MNP). followed by the addition of dihydroxyfurmarate (DHF) and Fe⁺³-ADP resulted in the generation and detection of radical adducts of this spin trap. Spin trapping of the alkyl radicals with 2-methyl-2-nitrosopropane led to the identification of methyl radical adduct following exposure to DHF/Fe⁺³-ADP. With sarcolemma and the alkyl nitroso compound, the only radical product trapped was the methyl radical formed by β-scission of alkoxyl radical. The participation of hydroperoxide-derived radicals in this system verified that the decomposition of unsaturated hydroperoxy fatty acid does proceed via a free radical mechanism.     

Down‐regulation of catalase activity allows transient accumulation of a hydrogen peroxide signal in Chlamydomonas reinhardtii

In photosynthetic organisms, excess light is a stress that induces production of reactive oxygen species inside the chloroplasts. As a response, the capacity of antioxidative defence mechanisms increases. However, when cells of Chlamydomonas reinhardtii were shifted from dark to high light, a reversible partial inactivation of catalase activity was observed, which correlated with a transient increase in the level of H₂O₂ in the 10 μm range. This concentration range seems to be necessary to activate H₂O₂‐dependent signalling pathways stimulating the expression of H₂O₂ responsive genes, such as the heat shock protein HSP22C. Catalase knock‐down mutants had lost the transient accumulation of H₂O₂, suggesting that a decrease in catalase activity was the key element for establishing a transient H₂O₂ burst. Catalase was inactivated by a one‐electron event consistent with the reduction of a single cysteine. We propose that under high light intensity, the redox state of the photosynthetic electron transport chain is sensed and transmitted to the cytosol to regulate the catalase activity. This allows a transient accumulation of H₂O₂, inducing a signalling event that is transmitted to the nucleus to modulate the expression of chloroplast‐directed protection enzymes.     

Studies on the antioxidant activity of some thiazolidinedione,imidazolidinedione and rhodanine derivatives having a flavone core

A series of flavonyl‐2,4‐thiazolidinedione, imidazolidinedione and rhodanine derivatives were tested for their antioxidant activity as scavengers of oxygen free radicals. Free radical scavenging activities, including superoxide anion radical , hydroxyl radical (HO^?) and 2,2′‐diphenyl‐1‐picrylhydrazyl free radical have been evaluated using chemiluminescence, electron paramagnetic resonance and spin trapping with 5,5‐dimethyl‐1‐pyrroline‐1‐oxide as a spin trap. Potassium superoxide in dimethylsulfoxide and 18‐crown‐6 ether were used for the production of . Hydroxyl radical was generated using the Fenton reaction. Ten of the eleven examined compounds exhibited decrease in chemiluminescence, but there were large differences in the decrease, ranging from 16% to 89%; also, two of these compounds increased light emission by about 200%. On the contrary, all compounds tested exhibited 30–68% scavenging HO^? and 25–96% scavenging the DPPH^? radical respectively. Possible mechanisms are proposed to explain the results. Copyright © 2014 John Wiley & Sons, Ltd.     

Posttranslational oxidative modification of (R)‐2‐(2,4‐dichlorophenoxy)propionate/α‐ketoglutarate‐dependent dioxygenases (RdpA) leads to improved degradation of 2,4‐dichlorophenoxyacetate (2,4‐D)

Microbial activities and the versatility gained through adaptation to xenobiotic compounds are the main biological forces to counteract environmental pollution. The current results present a new adaptive mechanism that is mediated through posttranslational modifications. Strains of Delftia acidovorans incapable of growing autochthonously on 2,4‐dichlorophenoxyacetate (2,4‐D) were cultivated in a chemostat on 2,4‐D in the presence of (R)‐2‐(2,4‐dichlorophenoxy)propionate. Long‐term cultivation led to enhanced 2,4‐D degradation, as demonstrated by improved values of the Michaelis–Menten constant K_m for 2,4‐D and the catalytic efficiency k_cat/K_m of the initial degradative key enzyme (R)‐2‐(2,4‐dichlorophenoxy)propionate/α‐ketoglutarate‐dependent dioxygenases (RdpA). Analyses of the rdpA gene did not reveal any mutations, indicating a nongenetic mechanism of adaptation. 2‐DE of enzyme preparations, however, showed a series of RdpA forms varying in their pI. During adaptation increased numbers of RdpA variants were observed. Subsequent immunoassays of the RdpA variants showed a specific reaction with 2,4‐dinitrophenylhydrazine (DNPH), characteristic of carbonylation modifications. Together these results indicate that posttranslational carbonylation modified the substrate specificity of RdpA. A model was implemented explaining the segregation of clones with improved degradative activity within the chemostat. The process described is capable of quickly responding to environmental conditions by reversibly adapting the degradative potential to various phenoxyalkanoate herbicides.     

Synthesis and activity of a coumarin‐based fluorescent probe for hydroxyl radical detection

As a type of reactive oxygen species (ROS), hydroxyl radical (·OH) is closely associated with many kinds of diseases. The present study aimed to develo p a novel OH fluorescent probe based on coumarin, a new compound that has not been previously reported. This probe exhibited good linear range and selectivity for ·OHl, and is able to avoid interference from some metal ions and other kinds of ROS (H₂O₂, O₂^.‐, ¹O₂, and HClO). Meanwhile, this probe has been used to evaluate the ·OH‐scavenging efficiency of different compounds, such as isopropyl alcohol, cytosine, uracil, Tempo, Glutathione (GSH), and dimethyl sulfoxide (DMSO). Therefore, the present study shows that this probe not only can effectively measure the level of ·OH, but also can assess the ·OH‐scavenging efficiency of different compounds. Furthermore this current study suggested that following further optimization, this probe may be potentially applied in the diagnosis of oxidative stress in human body.     

Magnesium methoxide‐induced chemiluminescent decomposition of bicyclic dioxetanes bearing a 2′‐alkoxy‐2‐hydroxy‐1,1′‐binaphthyl‐7‐yl moiety

Bicyclic dioxetanes 2a–c bearing a 2′‐alkoxy‐2‐hydroxy‐1,1′‐binaphthyl‐7‐yl moiety were effectively synthesized and their base‐induced chemiluminescent decomposition was investigated by the use of alkaline metal (Na⁺ and K⁺) or Mg²⁺ alkoxide in MeOH. When 2a–c were treated with tetrabutylammonium fluoride (TBAF) in dimethyl sulfoxide (DMSO) as a reference system, they showed chemiluminescence as a flash of orange light (maximum wavelength λ_max^CL = 573–577 nm) with efficiency Φ^CL = 6–8 × 10^–2. On the other hand, for an alkaline metal (Na⁺ or K⁺) alkoxide/MeOH system, 2a–c decomposed slowly to emit a glow of chemiluminescence, the spectra of which were shifted slightly toward red from the TBAF/DMSO system, and Φ^CL (= 1.4–2.3 × 10^–3) was considerably decreased. In addition, Mg(OMe)₂ was found to play a characteristic role as a base for the chemiluminescent decomposition of 2a–c through coordination to the intermediary oxidoaryl‐substituted dioxetanes 13. Thus, Mg²⁺ increased Φ^CL to more than twice those with Na⁺ or K⁺, while it shifted λ_max^CL considerably toward blue (λ_max^CL = 550–566 nm). Copyright © 2012 John Wiley & Sons, Ltd.     

New approach for stability study and determination of fluvoxamine in raw materials and pharmaceuticals through condensation with 2,2‐dihydroxyindane‐1,3‐dione

The present study describes the validation of a selective spectroscopic method for assay of fluvoxamine maleate (FXM). The validated method relies on condensation of FXM with 2,2‐dihydroxyindane‐1,3‐dione and phenylacetaldehyde using Teorell–Stenhagen buffer (pH 6.6) to give coloured fluorescent product measured at 482 nm using 386 nm as the excitation wavelength. The parameters influencing the reaction were studied precisely and adjusted accurately. The constructed calibration graph appeared rectilinear over the following range (0.8–14 μg ml^?1) and the estimated limit of detection was 0.25 μg ml^?1. Two pharmaceutical products from the Egyptian market were assayed using the suggested method and the final results agreed with measurements from other reported methods. Moreover, the drug was subjected to diverse stress conditions including acidic, alkaline, thermal, and photolytic degradation to examine the FXM stability. Directives from the International Conference on Harmonisation guidelines were applied to establish the validity of the work.     

A flow‐injection chemiluminescent method for the evaluation of the antioxidant activity of 5′‐nucleotides

In the present work, a simple chemiluminescence (CL) method coupled with flow‐injection analysis for the evaluation of antioxidant activity of 5′‐nucleotides (5′‐AMP, 5′‐CMP, 5′‐GMP, 5′‐UMP) was proposed. It is based on inhibition effect of the studied substances on CL emission of luminol–potassium ferricyanide–pyrogallol. Experiments were performed to evaluate the nature of the inhibition by 5′‐nucleotides of the CL reaction and their antioxidant activities. Based on the experimental results, it was observed that 5′‐nucleotides are available antioxidants that could effectively scavenge superoxide anion free radicals in a concentration‐dependent way. This will provide a basis for further development of the use of nucleotides. Copyright © 2009 John Wiley & Sons, Ltd.     

Free radical generation by skeletal muscle of adult and old mice: effect of contractile activity

Oxidative modification of cellular components may contribute to tissue dysfunction during aging. In skeletal muscle, contractile activity increases the generation of reactive oxygen and nitrogen species (ROS). The question of whether contraction-induced ROS generation is further increased in skeletal muscle of the elderly is important since this influences recommendations on their exercise participation. Three different approaches were used to examine whether aging influences contraction-induced ROS generation. Hind limb muscles of adult and old mice underwent a 15-min period of isometric contractions and we examined ROS generation by isolated skeletal muscle mitochondria, ROS release into the muscle extracellular fluid using microdialysis techniques, and the muscle glutathione and protein thiol contents. Resting skeletal muscle of old mice compared with adult mice showed increased ROS release from isolated mitochondria, but no changes in the extracellular levels of superoxide, nitric oxide, hydrogen peroxide, hydroxyl radical activity or muscle glutathione and protein thiol contents. Skeletal muscle mitochondria isolated from both adult and old mice after contractile activity showed significant increases in hydrogen peroxide release compared with pre-contraction values. Contractions increased extracellular hydroxyl radical activity in adult and old mice, but had no significant effect on extracellular hydrogen peroxide or nitric oxide in either group. In adult mice only, contractile activity increased the skeletal muscle release of superoxide. A similar decrease in muscle glutathione and protein thiol contents was seen in adult and old mice following contractions. Thus, contractile activity increased skeletal muscle ROS generation in both adult and old mice with no evidence for an age-related exacerbation of ROS generation.     

A novel chemiluminescent flow‐injection analysis of transferrin by its reduction of the luminol—hydrogen peroxide reaction catalysed by meso‐tetra‐(3‐methoxyl‐4‐hydroxyl) phenyl manganese porphyrin

Based on the inhibition effect of transferrin (Tf) on the reaction of the luminol–hydrogen peroxide (H₂O₂) chemiluminescence (CL) system, catalysed by meso‐tetra‐(3‐methoxyl‐4‐hydroxyl) phenyl manganese porphyrin (MnP) as a mimetic enzyme of peroxides, a sensitive flow‐injection CL method has been developed for the determination of Tf in an alkaline medium. The CL reaction was carefully investigated by examining the variations of reaction conditions. Under optimum conditions, the linear range for the determination of transferrin was 0.04–20.0 μg/mL and the detection limit was 1.62 ng/mL. This proposed method was sensitive, convenient and simple, and has been successfully applied to the determination of transferrin in a serum sample. Copyright © 2011 John Wiley & Sons, Ltd.