Coordination chemical studies on metalloenzymes. II. Kinetic behavior of various types of chelating agents towards bovine carbonic anhydrase.

In order to investigate the kinetics and mechanism of the removal of zinc ions from bovine carbonic anhydrase [EC 4.2.1.1] (BCA), several chelating agents with various stability constants were used to remove zinc from BCA. The second-order rate constants (kaap) of zinc removal from BCA were found to be in the following order; 2,6-pyridinedicarboxylic acid greater than 2-pyridinecarboxylic acid greater than 2,4-pyridinedicarboxylic acid greater than 2,3-pyridinedicarboxylic acid greater than or approximately 1,10-phenanthroline greater than or approximately 5-methyl-1,10-phenanthroline greater than 2,2'-bipyridine. With similar chelating agents the greater the stability constant, the faster was the rate of removal of zinc ions from BCA. With EDTA, trans-1,2-cyclohexanediaminetetraacetic acid, and nitrilotriacetic acid, the rate of zinc ion removal from the native enzyme was governed by the rate of spontaneous dissociation of zinc enzyme. The rate constants for the removal of zinc ions from BCA were governed by the affinity of the chelating agents for the metal ion and the conformation of the chelating agents. Based on these findings, reaction pathways for various chelating agents are proposed.     

Studies on porphyrinogen carboxy-lyase from chick embryo liver

The purpose of the present work was to find the optimal conditions for the assay of chick embryo liver porphyrinogen carboxy-lyase. The enzyme activity was studied as a function of protein and substrate concentrations, time, pH value and incubation temperature. The effects of reduced glutathione (GSH), ethylenediaminetetra-acetate (EDTA), oxygen and several chemical compounds such as pyridoxal phosphate, sodium and potassium halogenated salts, sulph - hydryl reagents, chelating agents and ferrous iron were also investigated. The following results were found: (1) The optimal protein concentration was 1.25-2.5 mg/ml. For the substrate uroporphyrinogen III, the best concentration was 2 mumol/l; a slight inhibition was found at higher substrate concentrations. (2) The optimal pH value was 6.8 for both stages of uroporphyrinogen III decarboxylation ( octacarboxylic first stage----heptacarboxylic second stage---- tetracarboxylic porphyrinogen). (3) The activity increased with the incubation temperature (25-60 degrees C). (4) The enzyme activity was not enhanced by the addition of GSH or other sulph - hydryl reagents (cysteine and dithiothreitol), nor by the incorporation of EDTA or other chelating agents (Na-diethyldithiocarbamate, alpha,alpha'-bipyridyl and Na-pyrophosphate). (5) Oxygen diminished the second stage of decarboxylation. (6) Pyridoxal phosphate seems not to be a cofactor necessary in the decarboxylation. (7) NaCl or KCl diminished the activity in higher degree than did NaF or KF; the second stage was, in all cases, more affected than the first. (8) FeSO4 slightly diminished the second stage of uroporphyrinogen III decarboxylation at concentrations of 0.05 and 0.15 mmol/l, but both stages were significantly decreased at 0.3 mmol/l.     

In vitro antioxidant activity of silymarin

Silymarin, a known standardized extract obtained from seeds of Silybum marianum is widely used in treatment of several diseases of varying origin. In the present paper, we clarified the antioxidant activity of silymarin by employing various in vitro antioxidant assay such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH·) scavenging, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination by Fe³⁺ ? Fe²⁺ transformation method and Cuprac assay, superoxide anion radical scavenging by riboflavin/methionine/illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe²⁺) chelating activities. Silymarin inhibited 82.7% lipid peroxidation of linoleic acid emulsion at 30 μg/mL concentration; butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and trolox indicated inhibition of 83.3, 82.1, 68.1 and 81.3% on peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, silymarin had an effective DPPH· scavenging, ABTS^√+ scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe³⁺) reducing power by Fe³⁺ ? Fe²⁺ transformation, cupric ions (Cu²⁺) reducing ability by Cuprac method, and ferrous ions (Fe²⁺) chelating activities. Also, BHA, BHT, α-tocopherol and trolox, were used as the reference antioxidant and radical scavenger compounds. Moreover, this study, which clarifies antioxidant mechanism of silymarin, brings new information on the antioxidant properties of silymarin. According to the present study, silymarin had effective in vitro antioxidant and radical scavenging activity. It could be used in the pharmacological and food industry because of its antioxidant properties.     

A chelate complex‐enhanced luminol system for selective determination of Co(II), Fe(II) and Cr(III)

A determination method for Co(II), Fe(II) and Cr(III) ions by luminol‐H₂O₂ system using chelating reagents is presented. A metal ion‐chelating ligand complex with a Co(II) ion and a chelating reagent like ethylenediaminetetraacetic acid (EDTA) produced highly enhanced chemiluminescence (CL) intensity as well as longer lifetime in the luminol‐H₂O₂ system compared to metals that exist as free ions. Whereas free Cu(II) and Pb(II) ions had a strong catalytic effect on the luminol‐H₂O₂ system, significantly, the complexes of Cu(II) and Pb(II) with chelating reagents lost their catalytic activity due to the chelating reagents acting as masking agents. Based on the observed phenomenon, it was possible to determine Co(II), Fe(II) and Cr(III) ions with enhanced sensitivity and selectivity using the chelating reagents of the luminol‐H₂O₂ system. The effects of ligand, H₂O₂ concentration, pH, buffer solution and concentrations of chelating reagents on CL intensity of the luminol‐H₂O₂ system were investigated and optimized for the determination of Co(II), Fe(II) and Cr(III) ions. Under optimized conditions, the calibration curve of metal ions was linear over the range of 2.0 × 10^‐8 to 2.0 × 10^‐5 M for Co(II), 1.0 × 10^‐7 to 2.0 × 10^‐5 M for Fe (II) and 2.0 × 10^‐7 to 1.0 × 10^‐4 M for Cr(III). Limits of detection (3σ/s) were 1.2 × 10^‐8, 4.0 × 10^‐8 and 1.2 × 10^‐7 M for Co(II), Fe(II) and Cr(III), respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

The effects of Al(III) speciation on the activity of trypsin

The effects of the different forms of Al(III) on the catalytic activity of the serine protease trypsin were studied. Enzyme activity was measured by BAEE assay in the presence of AlCl(3), Al(III):lactic acid 1:3, Al(III):maltol 1:3 or Al(III):nitrilotriacetic acid (NTA) 1:1 at a nominal Al(III) concentration of 0.01 M, and the ligand alone at pH 7.4 at 25 degrees C. Maltol and NTA caused approximately 30% inhibition, while that for the corresponding Al(III) complex was less than half of this. Al(III) in the form of the chloride or in three equivalents of lactic acid did not influence the activity of the enzyme, probably because most of the Al(III) was precipitated as Al(OH)(3). No direct interaction could be detected between the enzyme and the Al(III) complexes, either by ultrafiltration or by CD spectroscopy. These results strongly suggest that there is no direct involvement of Al(III) in the enzymatic reactions of trypsin.     

Antioxidant activity of bisbenzylisoquinoline alkaloids from Stephania rotunda: cepharanthine and fangchinoline

In the present study, we determined the antioxidant activity of cepharanthine and fangchinoline from Stephania rotunda by performing different in vitro antioxidant assays, including 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, N,N- dimethyl-p-phenylenediamine dihydrochloride (DMPD) radical scavenging, superoxide anion (O₂^?–) radical scavenging, hydrogen peroxide scavenging, total antioxidant activity, reducing power, and ferrous ion (Fe²⁺) chelating activities. Cepharanthine and fangchinoline showed 94.6 and 93.3% inhibition on lipid peroxidation of linoleic acid emulsion at 30 μg/mL concentration, respectively. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol, and trolox indicated inhibitions of 83.3, 92.2, 72.4, and 81.3% on peroxidation of linoleic acid emulsion at the same concentration (30 μg/mL), respectively. According to the results, cepharanthine and fangchinoline have effective antioxidant and radical scavenging activity.     

Kinetics and mechanism of dissimilative Fe(III) reduction by Pseudomonas sp. 200

The kinetics and mechanism of Fe(III) reduction to Fe(II) were studied in pure batch cultures of Pseudomonas sp. 200. The rate of iron reduction has been mechanistically related to aqueous phase iron speciation. In the absence of microbial activity the iron reduction rate was negligible. Initial rates of microbial iron reduction were accelerated more than 20-fold by the addition of equimolar quantities of nitrilotriacetic acid (NTA) to media initially containing 1.86 x 10(-3)M total Fe(III). Numerical techniques were utilized to quantify relationships between the observed rate of Fe(II) production and the calculated (equilibrium) aqueous phase speciation. These results indicate that soluble ferric iron species are not equivalent in terms of their susceptibility to bacterial (dissimilative) iron reduction. The concentration of Fe(NTA)(OH)(2) (2-) correlated strongly with observed iron reduction rates. Ferrous iron species appeared to inhibit the reduction process.     

EDTA activation of H2 photoproduction by Rhodospirillum rubrum

Summary The effect of trace elements (Fe, Ni) and chelating compounds on the activity of hydrogen (H₂) uptake (Hup) hydrogenase, nitrogenase and rate and yield of H₂ photoproduction from l-lactate in photosynthetic cultures of Rhodospirillum rubrum was investigated. Hup activity depended on the availability of Ni²⁺ and was inhibited by EDTA (0.3–0.5 mm ethylenedinitrilotetraacetic acid). Addition of EDTA (0.5 mm) to the culture medium caused a nearly complete inactivation of Hup activity and activation of nitrogenase, which was paralleled by a threefold increase in total H₂ photoproduced from lactate. Hup^– mutants, isolated by transposon Tn5 mutagenesis, produced maximally twofold more H₂ than the wild-type. Experiments with different chelating agents [EDTA, NTA (nitrilotriacetic acid), citrate, isocitrate] and varying concentrations of Fe²⁺ and Fe³⁺ showed that photosynthetic growth and nitrogenase activity of R. rubrum were strongly influenced by the iron supply. It is concluded that EDTA enhanced H₂ photoproduction by (I) inhibition of biosynthesis of Hup hydrogenase and (II) mobilization of iron, thereby activating the biosynthesis of the nitrogenase complex. Correspondence to: M. Kern     

Solubility and accumulation of metals in Chinese brake fern, vetiver and rostrate sesbania using chelating agents

Greenhouse experiments were conducted to study the effects of chelating agents on the growth and metal accumulation of Chinese brake fern (Pteris vittata L.), vetiver (Vetiveria zizanioides L.), and rostrate sesbania (Sesbania rostrata L.) in soil contaminated with arsenic (As), Cu, Pb, and Zn. Among the five chelating agents used [ethylenediaminetriacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA), oxalic acid (OA), and phytic acid (PA)], OA was the best to mobilize As, EDTA to mobilize Cu and Pb, and HEDTA to mobilize Zn from soil, respectively. The biomass of vetiver was the highest, followed by rostrate sesbania. All chelating agents inhibited the growth of Chinese brake fern and rostrate sesbania, but HEDTA significantly increased the aboveground biomass of vetiver. Dry weights of both Chinese brake fern and rostrate sesbania decreased with increasing EDTA concentrations amended in the soil, especially in treatments with high EDTA concentrations. EDTA and HEDTA enhanced Cu, Zn, and Pb, but lowered As accumulation in all three plant species, except for As in vetiver, while OA significantly enhanced As accumulation in the aboveground part of vetiver. Concentrations of Cu, Zn, and Pb in the aboveground parts of plants increased significantly with the increase of EDTA concentrations and treatment time. In addition to As, Chinese brake fern also accumulated the highest Cu, Pb, and Zn in its aboveground parts among the three plant species grown in metal-contaminated soil with EDTA/HEDTA treatments. This species, therefore, can be used to simultaneously clean up As, Cu, Pb, and Zn from contaminated soils with the aid of EDTA or HEDTA.     

Analysis of lipid peroxidation mechanisms in human spermatozoa

The mechanisms by which ferrous ion promoters induce malondialdehyde generation by human spermatozoa have been investigated in order to provide a rational basis for the quantification and interpretation of lipid peroxidation assays. Incubation of human spermatozoa with a ferrous ion promoter in the presence of thiobarbituric acid (TBA) led to the generation of the bone fide malondialdehyde-TBA adduct. The importance of iron in the stimulation of lipid peroxidation was emphasized by the ability of Desferal* and EDTA to suppress malondialdehyde generation. Paradoxically, when the concentration of EDTA relative to iron was equimolar or greater, the suppression of malondialdehyde formation was accompanied by the generation of hydroxyl radicals. These results suggested that the addition of promoter did not effect the first-chain initiation of lipid peroxidation but favored an alternative mechanism involving the catalytic decomposition of pre-existing lipid peroxides. This conclusion was reinforced by the inability of reagents that would limit the formation (superoxide dismutase and/or catalase) or availability (mannitol, formate) of hydroxyl radicals, to influence malondialdehyde generation. While hydroxyl radicals were not directly involved in Fe²⁺-promoted malondialdehyde generation, the existence of significant correlations between reactive oxygen species production and the outcome of the TBA assay, suggested that Fenton chemistry might be important in the initiation of peroxidative damage. It is proposed that the impeded propagation of peroxidation initiated by Fenton or Haber Weiss reactions would lead to the accumulation of lipid peroxides in the spermatozoa and it is these peroxides that are induced to decompose during the Fe²⁺-promoted TBA assay, stimulating a lipoperoxidative chain reaction and malondialdehyde formation. © 1993 Wiley-Liss, Inc.     

Peroxide-dependent and -independent lipid peroxidations catalyzed by chelated iron.

Oxidation of linoleic acid (LA) in tetradecyltrimethylammonium bromide micelles was induced by ferrous- and ferric-chelates in the presence of linoleic acid hydroperoxide (LOOH). Ferrous-chelates also induced lipid peroxidation in the presence of H2O2, but ferric-chelates did not, thought they could generate OH-radicals in the presence of H2O2, resulting in deoxyribose degradation. Of the chelators tested, nitrilotriacetic acid (NTA) chelated with iron showed the highest activity for induction of H2O2- and LOOH-dependent lipid peroxidations and H2O2-dependent deoxyribose degradation. NTA with ferrous ion, but not with ferric ion, also initiated oxidation of LA after a short lag period in the absence of peroxides such as H2O2 and LOOH, but other chelators with ferrous ion did not. The peroxide-independent lipid peroxidation and associated oxidation of ferrous-NTA to ferric-NTA progressed in two steps: an induction step in a lag period and then a propagation step. Ferrous ion complexed with NTA was autoxidized pH-dependently and synchronously with oxygen uptake. The rates of both reactions increased with increase of pH, but were not related to the length of the lag period, which was also dependent on pH, and was shortest at pH 4.2. The EPR spectrum of the ferric-NTA complex prepared directly from ferric salt was different from that of the complex prepared from ferrous salt, confirming that some ferric-type active oxygen participated in induction of peroxide-independent lipid peroxidation. From these results, we propose a possible mechanism of lipid peroxidation induced by ferrous-NTA without peroxides. The finding that iron-NTA had the highest activity for induction of the oxidations of LA and deoxyribose is discussed in relation to the carcinogenic and nephrotoxic effects of this chelating agent.     

Metmyoglobin reductase. Identification and purification of a reduced nicotinamide adenine dinucleotide-dependent enzyme from bovine heart which reduces metmyoglobin.

Beef heart muscle has been found to contain an enzyme which will rapidly and directly reduce metmyoglobin in vitro. Reduction rates are far greater than any previously reported for nonspecific or nonenzymatic systems. The enzyme is NADH-dependent and requires the presence of ferrocyanide ion for in vitro assay. The artificial electron carriers, dichlorophenolindophenol and methylene blue, are not required. Nonenzymatic reduction of metmyoglobin, which has previously been reported, was not encountered under the assay conditions described herein. Demonstration of enzymatic activity is dependent on a suitable myoglobin substrate, NADH, and ferrocyanide. An equimolar amount of cytochrome b5 was more effective than ferrocyanide in the enzymatic reduction of metmyoglobin. The methods for preparation of beef heart myoglobin and for purification of the enzyme are presented. The enzyme has been purified over 2000-fold. The enzyme has a pH optimum about 6.5 and a Km of 5.0 x 10(-5) M, and is unaffected by the absence of O2. Sodium dodecyl sulfate-gel electrophoresis revealed a molecular weight around 30,000. Purified enzyme does not react with lipoamide. The reaction is markedly influenced by the composition of the buffering milieu. Enzyme activity is inhibited by p-chloromercuriphenyl sulfonic acid, quinacrine dihydrochloride, and N-ethyl-maleimide. Activity was slightly stimulated by FMN. The characteristics of the enzymatic activity and the assay system are similar to those reported by Hegesh et al. (J. Lab. Clin. Med. 72, 339-344, 1968) for erythrocyte methemoglobin reductase.     

Purification and characterization of purple acid phosphatase from developing rat bone

Tartrate-resistant acid phosphatase active on nucleoside di- and triphosphate substrates was isolated from developing rat bone and purified 2500-fold. The enzyme concentration had a purple coloration and activity that was sensitive to reducing agents. Mild reducing agents such as ferrous ion and ascorbic acid caused loss of purple color and increased activity toward substrates severalfold; however, a strong reductant such as dithionite caused loss of both color and activity which were partially restored by addition of ferrous ion and ascorbic acid. Enzyme activity was homogeneous with protein during the final gel permeation steps of chromatography and gave an apparent molecular size of about 40,000 Da. Determination of iron in the most pure preparation revealed the presence of 1.3 atoms of iron per molecule of the tartrate-resistant enzyme E2. Other properties of the purified enzyme include a pI of approximately 9.5 and sensitivity to inhibition by ions of copper, zinc, fluoride, and molybdate. Antibody prepared to the pre-concanavalin A (Con A)-Sepharose purified enzyme reacted with all protein from the Con A step, but it did not react with tartrate-sensitive acid phosphatase from rat bone or with potato acid phosphatase. Purple acid phosphatase from rat bone has many properties that parallel the iron-containing purple acid phosphatases from rat spleen, bovine spleen, and pig uterine secretions.     

Determination of free Ca ion concentrations with an ion-selective electrode in the presence of chelating agents in comparison with calculated values.

Experimentally determined free Ca ion concentrations, measured with a Ca-selective electrode, were compared with values calculated with a computer program utilizing stability constants of the chelating agents: NTA, EDTA, and EGTA used to set the free ion concentration in the range of 10^?3 to 10^?6m. In the presence of 0.1 m KCl, 2 mm MgCl₂, 20 mm Hepes (pH 7.4), 2 mm ATP, 0.1 mm CaCl₂ (total concentration), and various ligand concentrations the measured free Ca²⁺ levels were found to be approximately six to seven times greater than the computer-derived values. Apparent stability constants for Ca-ATP, Ca-EDTA, and Ca-EGTA were determined under these experimental conditions.     

Role of ferric iron in platelet lipoxygenase activity

Four iron chelating agents, EDTA, EGTA, ferron and orthophenan-throlene, were found to inhibit human platelet lipoxygenase activity in a dose-dependent manner. The inhibition produced by these chelators could be selectively reversed by the addition of ferric ion but not ferrous ion. The ID₅₀ for lipoxygenase activity directly correlated with the avidity of these compounds for ferric ion. Thus, human platelet lipoxygenase requires ferric ion for activity.     

The effect of diabetes, nutritional factors, and sex on rat liver and kidney mevalonate kinase, mevalonate-5-phosphate kinase, and mevalonate-5-pyrophosphate decarboxylase

Isopycnic sucrose gradient separation of rat liver organelles revealed the presence of two distinct branched-chain α-keto acid decarboxylase activities; a mitochondrial activity, which decarboxylates the three branched-chain α-keto acids and requires CoA and NAD⁺ and a cytosolic activity, which decarboxylates α-ketoisocaproate, but not α-ketoisovalerate, or α-keto-β-methylvalerate. The latter enzyme does not require added CoA or NAD⁺. Assay conditions for the cytosolic α-ketoisocaproate decarboxylase activity were optimized and this activity was partially characterized. In rat liver cytosol preparations this activity has a pH optimum of 6.5 and is activated by 1.5 m ammonium sulfate. The decarboxylase activity has an apparent K_m of 0.03 mm for α-ketoisocaproate when optimized assay conditions are employed. Phenylpyruvate is a very potent inhibitor. α-Ketoisovalerate, α-keto-β-methylvalerate, α-ketobutyrate, and α-ketononanoate also inhibit the α-ketoisocaproate decarboxylase activity. The data indicate that the soluble α-ketoisocaproate decarboxylase is an oxidase. Rat liver cytosol preparations consumed oxygen when either α-ketoisocaproate or α-keto-γ-methiolbutyrate were added. None of the other α-keto acids tested stimulated oxygen consumption. 1-¹⁴C-Labeled α-keto-γ-methiolbutyrate is also decarboxylated by cytosol preparations. The α-ketoisocaproate oxidase was purified 20-fold from a 70,000g supernatant fraction of a rat liver homogenate. In these preparations the activity was increased 4-fold by the addition of dithiothreitol, ferrous iron, and ascorbate. The major product of this enzyme activity is β-hydroxyisovalerate. Isovalerate is not a free intermediate in the reaction. The data indicate an alternative pathway for metabolism of α-ketoisocaproate which produces β-hydroxyisovalerate.     

3D molecular modeling, free radical modulating and immune cells signaling activities of the novel peptidomimetic L-glutamyl-histamine: possible immunostimulating role

An original representative of the patented by author family of histamine-containing peptidomimetics L-glutamyl-histamine (L-Glu-Hist) was synthesized and characterized as a biologically active compound with a role of cytokine mimic leading to cellular responses of improved specificity. The study assesses the ability of L-Glu-Hist to affect molecular modeling, modulate free radical activity and influence immune cell signaling. The energy-minimized 3D conformations of L-Glu-Hist derived from its chemical structure resulted in stabilization for Fe2+ chelating complexes. L-Glu-Hist accelerated the decrease of ferrous iron in the ferrous sulfate solution in a concentration-dependent mode and showed the ferroxidase-like activity at concentrations less than 3 mM in the phenanthroline assay, whereas in the concentration range 3-20 mM L-Glu-Hist restricted the availability of Fe2+ to phenanthroline due to binding of ferrous ions in chelating complexes. L-Glu-Hist showed stimulatory effect on phosphatidylcholine liposomal peroxidation (LPO) catalyzed by the superoxide anion radical (O2*-)-generating system (Fe2+ + ascorbate) at low (less or about 1 mM) L-Glu-Hist concentrations and both revealed the inhibitory effect on LPO in this system of high (approximately 10 mM) L-Glu-Hist concentration. The stimulation of LPO by L-Glu-Hist was related to the ability of peptidomimetic in small (approximately 0.05 mM) concentrations to release O2*- free radicals as determined by the superoxide dismutase-inhibitable cytochrome c reduction assay. O2*- release by L-Glu-Hist might result from its ferroxidase-like activity, while inhibition of LPO by L-Glu-Hist was caused by its chelating activity to Fe2+ ions, prevention of free radical generation and lipid hydroperoxide-degrading ability of 5-20 mM L-Glu-Hist. L-Glu-Hist released O2*- in concentrations which stimulated [3H]-thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and mononuclear cells from human blood. L-Glu-Hist modulates the ability of oxygen free radicals to act as signaling agents at low concentrations, influencing gene expression. The structural peptide-like analogues of L-Glu-Hist such as L-Glu-Trp, carcinine (beta-alanylhistamine), but not L-Pro-Glu-Trp were active in stimulating thymidine incorporation and in inducing proliferation of mononuclear cells as compared to mitogen concanavalin A at doses 2.5-25.0 microg/ml. Our data provide evidence that L-Glu-Hist may act as a very fast, specific and sensitive trigger for lymphocyte proliferation and immunoregulation. The cited abilities and further obtained in vivo results make Immudilin ((INCI: glutamylamidoethyl imidazole, aqueous solution), L-Glu-Hist) a useful immunoregulatory agent.     

Antioxidant characteristics of some potential anticataract agents. Studies of aspirin, paracetamol, and bendazac provide support for an oxidative component of cataract

It is conceivable that drugs with anticataract potential possess antioxidant activity. Using defined chelating agents and reducing agents in a number of assays for antioxidant activity, we have demonstrated that paracetamol, aspirin, bendazac, and its metabolite 5-hydroxybendazac possess substantial reducing and/or metal-chelating activity. We found that paracetamol and 5-hydroxybendazac reduced the diphenylpicrylhydrazyl free radical; inhibited butyl peroxide-induced erythrocyte lysis as well as the haematin-catalyzed oxidative coupling of 4-aminoantipyrine and phenol by butyl peroxide. Furthermore, paracetamol, bendazac, and aspirin competed with 3-(2-pyridyl)-5,6-Diphenyl-1,2,4-triazine-4', 4"-disulphonic acid (ferrozine) for ferrous ion.     

Specific effect of zinc ions on DNA polymerase activity of avian myeloblastosis virus

Summary The effect of selected cations on DNA synthesis by DNA-polymerase of avian myeloblastosis virus (AMV) was studied. Zinc ions at low concentration (0.2 mm) in the assay system enhanced the activity about 2 × fold and at higher concentration (2.0 mm) inhibited the activity completely. In contrast, addition of lithium and potassium salts produced inhibitory effects in this ionic concentration range. Replacement of K⁺ ion had an inhibitory effect on the activity.     

In vitro antioxidant activity of silymarin

Silymarin, a known standardized extract obtained from seeds of Silybum marianum is widely used in treatment of several diseases of varying origin. In the present paper, we clarified the antioxidant activity of silymarin by employing various in vitro antioxidant assay such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH(.)) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination by Fe3+ - Fe2+ transformation method and Cuprac assay, superoxide anion radical scavenging by riboflavin/methionine/illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe2+) chelating activities. Silymarin inhibited 82.7% lipid peroxidation of linoleic acid emulsion at 30 microg/mL concentration; butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol and trolox indicated inhibition of 83.3, 82.1, 68.1 and 81.3% on peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, silymarin had an effective DPPH(.) scavenging, ABTS(.)+ scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power by Fe3+-Fe2+ transformation, cupric ions (Cu2+) reducing ability by Cuprac method, and ferrous ions (Fe2+) chelating activities. Also, BHA, BHT, alpha-tocopherol and trolox, were used as the reference antioxidant and radical scavenger compounds. Moreover, this study, which clarifies antioxidant mechanism of silymarin, brings new information on the antioxidant properties of silymarin. According to the present study, silymarin had effective in vitro antioxidant and radical scavenging activity. It could be used in the pharmacological and food industry because of its antioxidant properties.