Go toArchive
Browse byFacets
Bookbag ( 0 )
'Free Radical' in keywords
Results  13 Items
Sorted by   
Publication Year
2000 (1)
1997 (1)
1994 (1)
1989 (2)
1986 (1)
1985 (1)
1983 (2)
1981 (1)
1980 (1)
1978 (1)
1Author    Purusotam Basnet3, TetsuyaM. Atsunob, Richard Neidlein3Requires cookie*
 Title    Potent Free Radical Scavenging Activity of Propol Isolated from Brazilian Propolis  
 Abstract    We evaluated free radical scavenging activity of the water, methanol and chloroform ex­ tracts of propolis in l,l-diphenyl-2-picrylhydrazyl (DPPH) free radical and xanthine-xanthine oxidase (XO D) generated superoxide anion assay systems. The free radical scavenging activ­ ity guided fractionation and chemical analysis led to the isolation of a new compound, propol {3-[4-hydroxy-3-(3-oxo-but-l-enyl)-phenyl]-acrylic acid) from the water extract, which was more potent than most common antioxidants such as vitamin C and vitamin E (a-tocopherol) in these assay systems. 
  Reference    Z. Naturforsch. 52c, 828—833 (1997); received August 7/September 19 1997 
  Published    1997 
  Keywords    Propol, Propolis, Free Radicals, Superoxide Anion, Antioxidative Activity 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/52/ZNC-1997-52c-0828.pdf 
 Identifier    ZNC-1997-52c-0828 
 Volume    52 
2Author    Claudia Bäk, Klaus PraefckeRequires cookie*
 Title    Photoreaktionen 2.2'-dihalogensubstituierter Benzoinether und Benzildimethylmonoketale in Lösung 1 Photoreactions of 2,2'-Dihalogen Substituted Benzoin Ether and Benzildimethylmonoketals in Solution  
 Abstract    The synthesis of a,a'-dihalogenated benzoin ether 6 and benzildimethylmonoketals 7 are discribed. Their reaction behavior under UV irradiation and electron impact conditions are discussed in comparison with those of arylesters 1 of seleno and thiobenzoic acid. The photoproducts of 6 and 7 are separated and identified with help of column or vaporphase chromatography. Photoinduced a-cleavages of 6 and 7 produce 2-halogenbenzoyl radicals 9 and a-monomethoxybenzyl radicals 10 or a,a-dimethoxybenzyl radicals 15 resp., which undergo four different stabilization reactions under formation of 1) 2-halogenbenzaldehydes 12 from 9 by hydrogenabstraction, 2) 2,2'-dihalogenbenzils 11 and l,2-di(2-chlorophenyl)-1,2-dimethoxyethan (13) via dimerization of 9 or 10 resp., 3) methylesters 16 of 2-halogen-benzoic acids by /^-elimination of methylradicals from 15, and 4) 2-halogenacetophenones 17 via combination of 9 with methylradicals from 15. In addition to these photoproducts 2-phenylbenzoic acidester 18, benzaldehyde (19), and acetophenone (20) are formed by photosubstitution of halogens in benzaldehydes 12 as well as in acetophenones 17 against hydrogen and in benzoic acid-esters 16 against phenyl resp. Independent photoexperi-ments prove 1) the formation of 2-phenylbenzoic acidester 18 by halogen-phenylreplace-ment in 16 and 2) that chlorine is easier than bromine, both in orZ/io-position to a carboxyl function, substituted by phenyl. No photoproducts {e.g. 8 or 14) are formed by substitution of halogen in the 2-halogenbenzoyl part of a-cleavage against neither a-monomethoxybenzyl nor a,a-dimethoxybenzylradicals resp. as expected like the photoinduced formation of selenoxanthones or thioxanthones 2 from selenol-or thiolesters 1. 
  Reference    (Z. Naturforsch. 33b, 106—112 [1978]; eingegangen am 5. Oktober 1977) 
  Published    1978 
  Keywords    Carbonyl Compounds, a-Cleavages, Free Radicals, Aromatic Photosubstitutions 
  Similar Items    Find
 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0106.pdf 
 Identifier    ZNB-1978-33b-0106 
 Volume    33 
3Author    Heinz-Peter Schuchmann, Rita Wagner, Clemens Von SonntagRequires cookie*
 Title    7-Radiolysis of 2'-Deoxycytidine-5'-phosphate in Deoxygenated Aqueous Solutions. OH Radical-Induced Alterations at the Sugar Moiety  
 Abstract    In order to elucidate some aspects of the mechanism of radical-induced strand break formation in DNA, the y-radiolysis of N20-saturated aqueous solutions of 2'-deoxycytidine-5'-phosphate has been studied as a model system. At pH 4 it has been observed that upon OH attack at the sugar moiety phosphate (G ^ 0.6) and cytosine (G = 1) are released and the following cytosine-free sugars are formed: 2,5-dideoxypentos-3,4-diulose, 1 (G = O.22), 2-deoxy-pentos-4-ulose, 2 (G = 0.1s), 2-deoxy-pentos-4-ulose-5-phosphate, 3 (G=0.06), 2-deoxypentonic acid-5-phosphate and its lactone, 5 (G «0.5). Some 2-deoxyribose-5-phosphate, 4 is also formed. Upon addition of H2O2 (up to 10 -2 M) prior to irradiation, G(l) is drastically reduced without giving rise to another cytosine-free product. G(3) increases at the expense of G(2). G (4 + 5) also increase upon H2O2 addition. The formation of these products and the change of their G values as a function of H2O2 concentration are discussed in the light of well-documented radical reactions of carbohydrates and related compounds. The precursor of 1 has been considered to be the radical at C-3', that of 2 and 3 the radical at C-4' and that of 5 the radical at C-l'. Product 4 is thought to arise from a radical-induced destruction of the cytosine moiety. These primary radicals which may undergo rearrangement, or eliminate phosphate, are readily oxidised by H202, a reaction which leads to the change of product distribution mentioned above. 
  Reference    Z. Naturforsch. 38b, 1213—1220 (1983); received June 27 1983 
  Published    1983 
  Keywords    Free Radicals, Radical Cations, Carbohydrates, DNA Model 
  Similar Items    Find
 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1213.pdf 
 Identifier    ZNB-1983-38b-1213 
 Volume    38 
4Author    PietroL. IndovinaRequires cookie*
 Abstract    We describe the appearance of a free-radical signal in the ESR spectrum of normal human serum incubated with several complement activating agents. The intensity o f this signal is dependent of dose of activating agents, time and temperature. Signals elicited by different complement activators differ in morphology and kinetics. Inhibition by treatment with EDTA and the presence o f the signal in activated C 6-deficient rabbit serum suggest that the con-vertase forming steps of complement activation (C2 to 5) could be the source of free-radical containing molecules. 
  Reference    Z. Naturforsch. 35c, 844—847 (1980); received May 12/June 16 1980 
  Published    1980 
  Keywords    Complement, Electron Spin Resonance, Free Radicals 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0844_n.pdf 
 Identifier    ZNC-1980-35c-0844_n 
 Volume    35 
5Author    A. HengleinRequires cookie*
 Title    Sonolysis of Carbon Dioxide, Nitrous Oxide and Methane in Aqueous Solution  
 Abstract    Water was irradiated with ultrasonic waves under an argon atmosphere which contained small amounts of carbon dioxide, nitrous oxide or methane. The yield of the products was measured as a function of the composition of the gas atmosphere. Maximum yields were observed at a few per cent of the added polyatomic gas. No chemical effects occurred in the irradiation under an atmosphere of pure C0 2 , N 2 0 or CH 4 . It is concluded that the gas mixture in the tiny gas bubbles, in which the chemical effects are brought about, is not in Henry's equilibrium with the aqueous gas solution. The main product of the sonolysis of C0 2 is CO, a small amount of formic acid also being formed. The sonolysis is explained by both the attack of H atoms from the sonolysis of water and direct decomposition of C0 2 due to the high temperatures existing in compressed gas bubbles. The main products of the sonolysis of N 2 0 are nitrogen, nitrite and nitrate. N 2 0 enhances the rate of various oxidations such as that of iodide, nitrite and propanol-2. In the methane containing solution, a lot of hydrogen is produced, the main oxidation products being ethane, ethylene, C 3 -and C 4 -hydrocarbons and carbon monoxide. A mechanism is postulated which involves both the attack on methane by radicals from the decomposition of water and thermal decomposition of methane. The local radical concentrations are so high that a methane molecule may undergo multiple radical attack. The similarity between sonolytic reactions and reactions occurring in flames is emphasized. 
  Reference    (Z. Naturforsch. 40b, 100—107 [1985]; received August 14 1984.) 
  Published    1985 
  Keywords    Ultrasonic Waves, Carbon Dioxide, Nitrous Oxide, Methane, Free Radicals 
  Similar Items    Find
 TEI-XML for    default:Reihe_B/40/ZNB-1985-40b-0100.pdf 
 Identifier    ZNB-1985-40b-0100 
 Volume    40 
6Author    WernerH. Kalus, WilliamG. FilbyRequires cookie*
 Title    Is there an Equilibrium between A scorbic and Dehydroascorbic Acids?  
 Abstract    The previously reported interaction between ascorbate monoanion and dehydroascorbic acid yielding semidehy-droascorbic acid has been shown to be therm odynam ically unfeasible and non-existent. N o evidence for radical for­ mation in the reinvestigation o f the reaction using ESR spectroscopy under careful exclusion o f air could be found. Our results show that the detection o f the free radical in earlier studies resulted from the reaction of ascorbate with traces of oxygen and/o r metals. 
  Reference    Z. Naturforsch. 36c, 1088—1090 (1981); received May 19 1981 
  Published    1981 
  Keywords    Ascorbic Acid, Dehydroascorbic Acid, Redox Potential, Free Radical, ESR 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-1088_n.pdf 
 Identifier    ZNC-1981-36c-1088_n 
 Volume    36 
7Author    Raimund Quint, RuthMaria Quint, Nikola Getoff, Tsvetan Gantchev, Maria ShopovaRequires cookie*
 Abstract    n d P h o to fr in I I in P o l a r a n d M ic ro h e te ro g e n e o u s E n v iro n m e n t Hematoporphyrin (HP) and its derivatives (HPD; e.g. photofrin II) are used as efficient sensitizers in the photodynamic treatment of tumors. The photoinduced formation of various transients result­ ing from these substrates at pH 12 and 7.4 were studied by conventional flash photolysis and by ESR techniques in the presence of various additives. EDTA is acting as an efficient reducing agent for the triplet state of the substrates. The absorption spectra of some transients (HP--, HP —OH, HPD'", HPD —OH) were obtained. Further, ESR studies (pH 4-7) showed that 3HP is mostly converted into HP' -in the presence of EDTA, but this is not the case with 3HPD. In airfree HPD solutions a longlived transient was registered, which was attributed to HPD'+ species. In aerated substrate solutions the singlet oxygen (0 2) and peroxyradicals are formed. The discussed transients very likely are involved in the photodynamic treatment of tumors in man. F la s h P h o to ly s is a n d E S R S tu d ie s on H e m a to p o r p h y rin 
  Reference    Z. Naturforsch. 44a, 283—290 (1989); received January 24 1989 
  Published    1989 
  Keywords    Hematoporphyrin (HP), Hematoporphyrin derivatives (HPD), Flash Photolysis, ESR, Free radicals 
  Similar Items    Find
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0283.pdf 
 Identifier    ZNA-1989-44a-0283 
 Volume    44 
8Author    FevziK. Öksal, M. Etin YavuzRequires cookie*
 Abstract    f s o m e I r r a d i a t e d A m m o n i u m C o m p o u n d s G am m a irradiation dam age centres in (N H 4)2SiF6, (N H 4)2SnCl6, (N H 4)2PtC l6, [(CH3)2N H 2]2SnCl6, (N H 4)2PdCl6 and ultraviolet irradiation damage centres in (CH 3)4N C H 3CO O and (C H 3)4N Br have been investigated by electron paramagnetic resonance spectroscopy. It has been found that the radicals produced in (N H 4)2SiF6 and (N H 4)2SnCl6 is N 2H 4 , and those in (N H 4)2P tC l6 are N H 3 and (P tC l6)3 -. In [(CH3)2N H 2]2SnCl6 the species is (C H 3)2N H + , and in (N H 4)2PdC l6 the species is (P dC l6)3 -. Furthermore, it has been shown that the ultraviolet irradia­ tion produces C H 3 and C 0 2 radicals in (C H 3)4N C H 3CO O and C H 3 radical in (C H 3)4NBr. The EPR parameters of the observed radicals have been determined. 
  Reference    Z. Naturforsch. 49a, 1159 (1994); received August 22 1994 
  Published    1994 
  Keywords    EPR, G am m a irradiation, Utraviolet, Ammonium com pounds, Free radicals 
  Similar Items    Find
 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-1159.pdf 
 Identifier    ZNA-1994-49a-1159 
 Volume    49 
9Author    G. Sosnovsky, E. H. ZaretRequires cookie*
 Title    Reactions of terf-Butylperoxy Esters. XV Decomposition of Dialkyl tert-Butylperoxy Phosphates 13  
 Abstract    Dialkyl The thermal decomposition of dialkyl £er£-butylperoxy phosphates, in the presence and absence of solvents, yields the corresponding dialkyl phosphate, acetone, methanol, 2,2-dimethoxypropane, and methyl isopropenyl ether as the primary products. Prolonged heating of the product mixture produces trialkyl phosphates, (R0)3P(0), which arise from the thermal decomposition of dialkyl phosphates. Data are presented to support a mechanism involving the heterolytic cleavage of the peroxide linkage. 
  Reference    (Z. Naturforsch. 31b, 820—831 [1976]; received November 20 1975) 
  Published    1976 
  Keywords    teri-Butylperoxy Phosphates, Tetraalkyl Pyrophosphates, Dialkyl Phosphates, Trialkyl Phosphates, Free Radicals 
  Similar Items    Find
 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0820.pdf 
 Identifier    ZNB-1976-31b-0820 
 Volume    31 
10Author    Komei Washino, Otmar Denk, Wolfram SchnabelRequires cookie*
 Title    O H Radical-Induced Main-Chain Scission of Poly(Ribonucleic Acids) under Anoxic Conditions  
 Abstract    Poly(ribonucleic acids), poly A, poly C and poly U, were irradiated in 0 2-free dilute aqueous solution at pH 7 to 8 with single pulses (50 to 200 ns) of 16MeV electrons. With the aid of Rayleigh light scattering measurements main-chain scission, induced by OH radicals, was observed with the three polynucleotides. From the time dependence of the decrease o f the light scattering intensity (LSI), the existence of two modes of decrease was inferred, indicating at least two different chemical mechanisms were operative in main-chain degradation. Evidence for the assignment o f the slow mode of LSI decrease to the lifetime of a free radical was obtained from quenching experiments with cysteamine. It is noteworthy, that the extent and the lifetime o f LSI decrease are not the same for the three polynucleotides. The differences indicate the influence of the chemical nature o f the bases on main-chain scission. Consequently, it is concluded that OH attack at carbons in 1' and/or 2' position of the ribose moiety contributes essentially to the degradation mechanism. 
  Reference    Z. Naturforsch. 38c, 100 (1983); received August 17/November 11 1982 
  Published    1983 
  Keywords    Poly(Ribonucleic Acids), OH Attack, Chain Breakage, Free Radicals, Time-Resolved Light Scattering 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0100.pdf 
 Identifier    ZNC-1983-38c-0100 
 Volume    38 
11Author    JankoN. Herak, Günter BehrensRequires cookie*
 Title    An in-situ Electron Spin Resonance Study  
 Abstract    ESR spectroscopy has been used to analyse the conformation of the radicals produced by the reaction of SOj with D-ribose (1), and 2-deoxy-D-ribose (6), at pH 1.3-5. From ribose three different types of radicals formed by H abstraction at C -l, C-2 and C-3 followed by a regio-selective a,ß-water elimination have been identified: the 2-deoxy-ribonolacton-2-yl (3), the 1-deoxy-pentopyranos-2-ulos-l-yl (4). and the 4-deoxy-pentopyranos-3-ulos-4-yl (2). Using deoxyribose two radicals of similar type, formed by H abstraction at C-3 and C-4 followed by water elimination, have been observed: the 2,4-dideoxy-3-ulos-4-yl (7) and the 2,3-dideoxy-4-ulos-3-yl (8). In addition, from both sugars an a-hydroxyalkyl radical has been identified based in part on the timing of their conformational motions: the ribos-3-yl (5) (the precursor of 2) and the 2-deoxy-ribos-l-yl (9), respectively. For radical 5 the rate constant k(e) for the water elimination and hence transformation into radical 2 was estimated. From the analysis of selective line broadening the frequencies of conformational changes of radicals 2 and 7 have been estimated. For 7 the frequencies of exchange of the two methylene groups were found to differ by more than 3 orders of magnitude. 
  Reference    Z. Naturforsch. 41c, 1062 (1986); received January 31 1986 
  Published    1986 
  Keywords    Free Radicals, Deoxy-D-ribose, D-Ribose, Conformational Kinetics, Electron Spin Resonance 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-1062.pdf 
 Identifier    ZNC-1986-41c-1062 
 Volume    41 
12Author    Stylianos Tsakiris3, Panagoula Angelogianni3, KleopatraH. Schulpisb, Panagiotis Behrakis3Requires cookie*
 Title    Protective Effect of L-Cysteine and Glutathione on Rat Brain Na+,K+-ATPase Inhibition Induced by Free Radicals  
 Abstract    The aim of this study was to investigate whether the preincubation of brain homogenates with L-phenylalanine (Phe), L-cysteine (Cys) or reduced glutathione (G SH) could reverse the free radical effects on N a+,K+-ATPase activity. Two well established systems were used for the production of free radicals: 1) F e S 0 4 (84 ^i m) plus ascorbic acid (400 |o.m) and 2) F e S 0 4, ascorbic acid and H20 2 (1 mM) for 10 min at 37 °C in hom ogenates o f adult rat whole brain. Changes in brain N a+,K+-ATPase activity and total antioxidant status (TAS) were studied in the presence of each system separately, with or without Phe, Cys or GSH. TAS value reflects the amount of free radicals and the capacity of the antioxidant enzymes to limit the free radicals in the homogenate. N a+,K+-ATPase was inhibited by 35 -5 0 % and TAS value was decreased by 5 0 -6 0 % by both systems of free radical production. The enzy­ matic inhibition was completely reversed and TAS value increased by 150-180% when brain homogenates were preincubated with 0.83 mM Cys or GSH. However, this N a+,K+-ATPase inhibition was not affected by 1.80 m M Phe, which produced a 4 5 -5 0 % increase in TAS value. It is suggested that the antioxidant action of Cys and GSH may be due to the binding of free radicals to sulfhydryl groups of the m olecule, so that free radicals cannot induce N a+,K+-ATPase inhibition. Moreover, Cys and GSH could regulate towards normal values the neural excitability and metabolic energy production, which may be disturbed by free radical action on N a+,K+-ATPase. 
  Reference    Z. Naturforsch. 55c, 271—2 (2000); received October 8/Decem ber 21 1999 
  Published    2000 
  Keywords    L-Cysteine, Reduced Glutathione, L-Phenylalanine, Free Radicals, N a+, K+-ATPase 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/55/ZNC-2000-55c-0271.pdf 
 Identifier    ZNC-2000-55c-0271 
 Volume    55 
13Author    Stanislaw Scheller, G. Razyna, G. AzdaRequires cookie*
 Title    The Ability of Ethanolic Extract of Propolis (EEP) to Protect Mice against Gamma Irradiation  
 Abstract    , W ojciech K rol*, Z en o n C zuba*, A lek san d er Z ajusz**, Janusz G ab ry s+, and Jashovam S h an i+ + *Departm ent o f M icrobiology and + Departm ent o f H istology and Em bryology, Silesian School of M edicine, Zabrze-Rokitnica, Poland; * in s titu te o f O ncology, G liwice, Poland, and ++School of Pharmacy, University o f Southern California, Los A n geles Ethanolic extract of propolis (E E P) was tested as a protective agent against gamma irradiation in mice. The mice were exposed to 6 Gy gamma irradiation from a " Co source, and were treated intraperitoneally with E E P, administered before and after their irradiation. W hile the non-treated mice expired within 12 w eeks, the mice that received a series of EEP treatm ents survived the irradiation, and their leucocyte count as well as their spleens' plaque-forming activity returned to normal. It is suggested that an antioxidant and a free radical scavanger in the E E P are responsible for the radiation protective effect of the extract o f this natural product. 
  Reference    Z. Naturforsch. 44c, 1049 (1989); received August 2/N ovem ber 3 1988 
  Published    1989 
  Keywords    Propolis, Radiation Protection, Free Radicals, E E P, A ntioxidant, G am ma Irradiation, Plaque Formation 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-1049.pdf 
 Identifier    ZNC-1989-44c-1049 
 Volume    44