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The American Journal of Chinese Medicine 1996The superoxide scavenging effects of fifteen coumarins were tested on the xanthine-xanthine oxidase-cytochrome C system. The results showed that fraxetin(10) displayed...
The superoxide scavenging effects of fifteen coumarins were tested on the xanthine-xanthine oxidase-cytochrome C system. The results showed that fraxetin(10) displayed the strongest activity, and its percent inhibition at 100, 10 and 1 muM were 100, 100 and 53.13% respectively. Esculetin(4) showed the second strongest activity resulting in percent inhibition at 100 and 10 muM were 87.16 and 52.38% respectively. Both fraxetin(10) and esculetin(4) have been isolated from the plant, Fraxinus bungeana DC (Oleaceae) which has been used in folk medicine as an analgesic and anti-inflammatory medicine. It seems that two phenolic hydroxy groups in the ortho position in the molecule of coumarins play an important role in scavenging activity.
Topics: Anions; Coumarins; Cytochrome c Group; Dose-Response Relationship, Drug; Superoxides
PubMed: 8739177
DOI: 10.1142/S0192415X96000037 -
Antioxidants & Redox Signaling Oct 2007Besides nitric oxide (NO), NO synthases (NOS) also produce superoxide ((*)O(2)()), a primary reactive oxygen species involved in both cell injury and signaling. Neuronal...
Besides nitric oxide (NO), NO synthases (NOS) also produce superoxide ((*)O(2)()), a primary reactive oxygen species involved in both cell injury and signaling. Neuronal NOS was first found to produce (*)O(2)(-) in vitro. Subsequent studies revealed (*)O(2)(-) generation as a common property of all NOS isoforms. Although NOS was originally shown to produce (*)O(2)(-) under defined conditions such as substrate or cofactor depletion, recent enzymatic studies found that the reduction of oxygen to (*)O(2)(-) is an obligatory step in NO synthesis. Tetrahydrobiopterin appears to play a key role in preventing (*)O(2)(-) release from the NOS oxygenase domain. On the other hand, the NOS reductase domain is also capable of producing significant amounts of (*)O(2)(-). Increasing evidence demonstrates that (*)O(2)(-) generation is involved in both physiological and pathological actions of NOS.
Topics: Animals; Catalysis; Humans; Nitric Oxide Synthase; Superoxides
PubMed: 17685851
DOI: 10.1089/ars.2007.1733 -
Talanta May 2015In the present work, a high-performance enzyme-based electrochemical sensor for the detection of superoxide anion radical (O2(●-)) is reported. Firstly, we employed a...
In the present work, a high-performance enzyme-based electrochemical sensor for the detection of superoxide anion radical (O2(●-)) is reported. Firstly, we employed a facile approach to synthesize PtPd nanoparticles (PtPd NPs) on chemically reduced graphene oxide (RGO) coated with polydopamine (PDA). The prepared PtPd-PDARGO composite was well characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectra, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical methods. Then the assembled composite was used as a desired electrochemcial interface for superoxide dismutase (SOD) immobilization. Owing to the PDA layer as well as the synergistic effect of PtPd NPs, the fabricated SOD/PtPd-PDARGO sensor exhibited an outstanding sensitivity of 909.7 μA mM(-1) cm(-2) upon O2(●-) in a linear range from 0.016 mM to 0.24 mM (R(2)=0.992), with a low detection limit of 2 μM (S/N=3) and excellent selectivity, good reproducibility as well as favorable long-term stability.
Topics: Biosensing Techniques; Electrochemistry; Electrodes; Graphite; Indoles; Metal Nanoparticles; Oxides; Palladium; Platinum; Polymers; Reproducibility of Results; Superoxide Dismutase; Superoxides
PubMed: 25770601
DOI: 10.1016/j.talanta.2015.01.009 -
Biochemical Pharmacology Jun 2006Oxypurinol, an inhibitor of xanthine oxidase (XO), is being studied to block XO-catalyzed superoxide radical formation and thereby treat and protect failing heart...
Oxypurinol, an inhibitor of xanthine oxidase (XO), is being studied to block XO-catalyzed superoxide radical formation and thereby treat and protect failing heart tissue. Allopurinol, a prodrug that is converted to oxypurinol by xanthine oxidase, is also being studied for similar purposes. Because allopurinol, itself, may be generating superoxide radicals, we currently studied the reaction of allopurinol with xanthine oxidase and confirmed that allopurinol does produce superoxide radicals during its conversion to oxypurinol. At pH 6.8 and 25 degrees C in the presence of 0.02 U/ml of XO, 10 and 20 microM allopurinol both produced 10 microM oxypurinol and 2.8 microM superoxide radical (determined by cytochrome C reduction). The 10 microM allopurinol was completely converted to oxypurinol, while the 20 microM allopurinol required a second addition of xanthine oxidase to complete the conversion. Fourteen percent of the reducing equivalents donated from allopurinol or xanthine reacted with oxygen to form superoxide radicals. Superoxide dismutase prevented the reduction of cytochrome C by these substrates. At higher xanthine oxidase concentrations, or at lower temperatures, more of the 20 microM allopurinol was converted to oxypurinol during the initial reaction. At lower xanthine oxidase concentrations, or higher temperatures, less conversion occurred. At pH 7.8, the amount of superoxide radicals produced from allopurinol and xanthine was nearly doubled. These results indicate that allopurinol is a conventional substrate that generates superoxide radicals during its oxidation by xanthine oxidase. Oxypurinol did not produce superoxide radicals.
Topics: Allopurinol; Free Radicals; Hydrogen-Ion Concentration; Superoxides; Temperature; Xanthine Oxidase
PubMed: 16650385
DOI: 10.1016/j.bcp.2006.02.008 -
Free Radical Research Dec 1999In this article, we address the mechanism of superoxide formation from constitutive nitric oxide synthases (NOS). Merits and drawbacks of the various superoxide... (Review)
Review
In this article, we address the mechanism of superoxide formation from constitutive nitric oxide synthases (NOS). Merits and drawbacks of the various superoxide detection assays are reviewed. One of the most viable techniques for measuring superoxide from NOS is electron spin resonance (ESR) spin-trapping using a novel phosphorylated spin trap. Implications of superoxide and peroxynitrite formation from NOS enzymes in cardiovascular and cerebrovascular disorders are discussed.
Topics: Animals; Cyclic N-Oxides; Doxorubicin; Electron Spin Resonance Spectroscopy; Humans; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Oxidation-Reduction; Spin Labels; Superoxides
PubMed: 10630684
DOI: 10.1080/10715769900301181 -
Methods in Enzymology 1999
Review
Topics: Blood Platelets; Humans; Methods; Nitric Oxide; Platelet Aggregation; Superoxides
PubMed: 9919554
DOI: 10.1016/s0076-6879(99)01069-1 -
Mikrochimica Acta Jun 2022The use of gold nanoparticles/superoxide dismutase (AuNP/SOD) bioconjugates is described as building blocks in SOD biosensor development for the quantification of...
The use of gold nanoparticles/superoxide dismutase (AuNP/SOD) bioconjugates is described as building blocks in SOD biosensor development for the quantification of superoxide in cell culture media. AuNP functionalization with 11-mercaptoundecanoic acid (MUA) and 4-mercaptobenzoic acid (MBA) (AuNP and AuNP) was used to improve SOD immobilization through EDC/NHS coupling using their -COOH terminus, leading to the formation of more stable bioconjugates. AuNP and AuNP/SOD bioconjugates were characterized by SEM to determine their size and morphology, UV-Vis for optical properties, FT-IR, and Raman spectroscopies for chemical functional group analysis and EDX for elemental analysis. Electrochemical methods were used to characterize the Au/AuNP-modified electrodes. For the optimization of the biosensor architecture, different AuNP/enzyme bioconjugates were prepared by varying the amount of both enzyme and AuNP, as well as their incubation time. Finally, the biosensors incorporating the bioconjugates were characterized by fixed potential amperometry and voltammetric analysis in order to establish the enzymatic mechanism and to elucidate the best biosensor architecture for monitoring superoxide in cell culture media. The best sensitivity value for superoxide detection corresponded to 41.2 nA µM cm, achieved by a biosensor based on AuNP/SOD bioconjugates monitored through fixed potential amperometry at 0.3 V vs. Ag/AgCl, with a limit of detection of 1.0 µM, and overall very good operational stability, maintaining 91% of the initial sensitivity after 30 days. Finally, the optimized biosensor was employed for the quantification of successive additions of superoxide in cell culture media, with excellent recovery values.
Topics: Gold; Metal Nanoparticles; Spectroscopy, Fourier Transform Infrared; Superoxide Dismutase; Superoxides
PubMed: 35674988
DOI: 10.1007/s00604-022-05352-z -
Advances in Experimental Medicine and... 1990
Review
Topics: Animals; Free Radical Scavengers; Humans; Superoxide Dismutase; Superoxides
PubMed: 2173879
DOI: 10.1007/978-1-4684-5730-8_7 -
Archives of Biochemistry and Biophysics Apr 2016The reaction between GSH and superoxide has long been of interest in the free radical biology. Early studies were confusing, as some reports suggested that the reaction...
The reaction between GSH and superoxide has long been of interest in the free radical biology. Early studies were confusing, as some reports suggested that the reaction could be a major pathway for superoxide removal whereas others questioned whether it happened at all. Further research by several investigators, including Helmut Sies, was required to clarify this complex reaction. We now know that superoxide does react with GSH, but the reaction is relatively slow and occurs mostly by a chain reaction that consumes oxygen and regenerates superoxide. Most of the GSH is converted to GSSG, with a small amount of sulfonic acid. As shown by Sies and colleagues, singlet oxygen is a by-product. Although removal of superoxide by GSH may be a minor pathway, GSH and superoxide have a strong physiological connection. GSH is an efficient free radical scavenger, and when it does so, thiyl radicals are generated. These further react to generate superoxide. Therefore, radical scavenging by GSH and other thiols is a source of superoxide and hydrogen peroxide, and to be an antioxidant pathway, there must be efficient removal of these species.
Topics: Glutathione; Humans; Sulfhydryl Compounds; Superoxides
PubMed: 27095219
DOI: 10.1016/j.abb.2015.11.028 -
Journal of Bioenergetics and... Aug 1999Based on our recent findings concerning the generating, partitioning, targeting, and functioning of superoxide in mitochondria, a hypothetical model involving a... (Review)
Review
Based on our recent findings concerning the generating, partitioning, targeting, and functioning of superoxide in mitochondria, a hypothetical model involving a "reactive oxygen cycle" in the respiratory chain has been proposed (Liu and Huang, 1991, 1996; Liu et al., 1996; Liu, 1997, 1998) This model emphasizes that during State 4 respiration, an interaction between an electron leak (a branch of electron transfer directly from the respiratory chain to form O2*-, but not H2O) and a proton leak (a branch pathway which utilizes delta muH+ to produce heat, but not ATP) may take place in cooperation with the Q and proton cycles in mitochondria through the consumption of H+ by O2*- anions to form a protonated perhydroxyl radical, HO2, which is directly permeable across the inner mitochondrial membrane and induces proton leakage and a decrease of delta muH+. O2*- generation in the mitochondrial respiratory chain and its cycling across the inner membrane may have the role of an endogenous protonophore in regulating and partitioning energy transduction and heat production, as well as in pathogenesis of mitochondrial diseases, aging, and apoptosis. The present article summarizes the supporting experimental evidence obtained in this laboratory and presents a brief description of the theoretical basis of this model.
Topics: Animals; Electron Transport; Humans; Mitochondria; Models, Biological; Protons; Reactive Oxygen Species; Superoxides
PubMed: 10665526
DOI: 10.1023/a:1018650103259