Since metals are cable of catalysing the free radical reactions, different metal (Mg, Mn, Zn) compounds were studied to determine their hydroxyl radical generating and/or scavenging abilities depending on ligand in a H2O2/•OH -luminol system with or without microperoxidase. Magnesium oxide, magnesium gluconate and manganese gluconate increase the free radical reactions in the H2O2/•OH -luminol system. Most of examined metal compounds have different hydroxyl radical scavenging activity in H2O2/•OH- microperoxidase -luminol system. Magnesium citrate has the highest antioxidant effect, while manganese compounds seem to be prooxidant. Vitamin E and C elevate the free radical level in this experimental system

Blázovics, Anna

Szentmihályi, Klára

Vinkler, Péter

English

Szentmihályi Klára

Blázovics Anna

Vinkler Péter

University of Szeged

Volume 47(1-4):107-109, 2003Acta Biologica Szegediensishttp://www.sci.u-szeged.hu/ABSSYMPOSIUM1Chemical Institute, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary, 22nd Department ofMedicine, Semmelweis University, Budapest, HungaryFree radical properties of metal complexes+Klára Szentmihályi1*, Anna Blázovics1,2, Péter Vinkler1ABSTRACT                        Since metals are cable of catalysing the free radical reactions, different metal(Mg, Mn, Zn) compounds were studied to determine their hydroxyl radical generating and/orscavenging abilities depending on ligand in a H2O2/•OH -luminol system with or withoutmicroperoxidase. Magnesium oxide, magnesium gluconate and manganese gluconate increasethe free radical reactions in the H2O2/•OH -luminol system. Most of examined metal compoundshave different hydroxyl radical scavenging activity in H2O2/•OH- microperoxidase -luminolsystem.  Magnesium citrate has the highest antioxidant effect, while manganese compoundsseem to be prooxidant. Vitamin E and C elevate the free radical level in this experimentalsystem. Acta Biol Szeged 47(1-4):107-109 (2003)KEY WORDSchemiluminescencefree radical generating abilityscavenging activitymagnesium, manganese and zinccompoundsAccepted April 30, 2003*Corresponding author. E-mail: szklari@chemres.hu+In memory of Profesor Béla Matkovics107In living organisms free radical formation and the free radicaldefense system are closely related to metal ions and com-plexes (Tampo and Yonaha 1992; Sigel and Sigel 1999).Fenton reaction describes Fe(II) induced hydroxyl radicalformation (Fenton 1894, Haber and Willstätter 1931, Haberand Weiss 1934) and other transition metal ions (e.g. V, Cr)take part in Fenton-like reactions (Halliwell and Gutteridge1990; Goldstein et al. 1993). Nevertheless, none transitionmetal ions also play a significant role, directly or indirectly,in free radical reactions. For example manganese, zinc andcopper have a role in the antioxidant defense system(Zidenberger-Cherr and Keen 1991; Ebadi et al. 1996) andmagnesium is present in every cell membrane in membraneATP-ase and magnesium activates several enzymes whichcatalyse polyphosphate hydrolysis (Fox et al. 2001).In the diseases where metal ion supplementation isneccessery, it is important to know the complex form (ligand)of the metal. The absorption of metal and other physico-chemical properties can change, depending on the ligand(Hallberg et al. 1970; Kaltwasser et al. 1987; Rauch et al.1990; Szentmihályi et al. 1998) and the physiological effectof the metal compound varies depending on the ligand aswell.Therefore, the hydroxyl radical generating ability andscavenging activity of some metal (Mg, Mn, Zn) compoundswere studied by chemiluminescence method in the H2O2-luminol system with or without microperoxidase.Materials and MethodsThe weight ratio of vitamin E to vitamin C was 1:2, and thatof vitamins to metals was 2:1 in the experimental system.Concentrations of the metal compounds in the basic solutionswere 1 mg/ml. The compounds examined were of phar-macopoeal quality. Since the result is matrix dependent, themeasurements were always made under same conditions(temperature, pH, concentration ratios).Chemiluminescence techniques were applied for thestudying of metal catalysis or scavenger activity. Lightemission of luminol was measured by a method of Blázovicset al. (1999) using a Berthold Lumat LB-9501 luminometer.The intensity of chemiluminescence light is given as therelative light unit (RLU).The reaction mixture for measuring free radical gener-ating ability was as follows: hydrogen peroxide (104  dilution)300 µl, luminol (7x10-7 M) 100 µl, the sample (1 mg metalcompound/ml solution) 50 µl and bidistilled water 250 µl.The reaction mixture for measuring the hydroxyl scav-enging activity was: hydrogen peroxide (104  dilution) 300 µl,microperoxidase (3x10-7 M) 300 µl, luminol (7x10-7 M) 50 µland the sample (1mg/ml ) 100 µl diluted with bidestilledwater to 1 ml. The intensity of chemiluminescence light isgiven as the relative light unit (RLU) reduced by free radicalscavenging substances.Results and DiscussionSince the decomposition of luminol in the presence ofhydrogen peroxide is catalysed by metal ions, some metalcompounds were investigated for the catalytic activity of thereaction.108Szentmihályi et al.In the applied system and concentrations neither vitaminsnor metal compounds (except for magnesium oxide, mag-nesium gluconate and manganese gluconate) generated thedecomposition of luminol to aminophtalate in H2O2/•OH-luminol system (Table 1). When we applied the microperox-idase in the system (H2O2/•OH-microperoxidase-luminol)different metal compounds have different radical scavengingactivity (Table 2). The metal ions, depending on the qualityof the metal, ligand and concentration, may induce freeradicals. Among magnesium compounds, only magnesiumcitrate has significant scavenging activity whereas othermagnesium compounds enhance the free radical level for-mation. None of the manganese compounds have hydroxylradical scavenging activity, while zinc compounds (except forzinc chloride) show scavenging activity. The mixture ofvitamin E and C in the applied concentration has only a weakscavenging activity in this system.The presence of vitamin E and C in the metal ion-containing solution changes the free radical scavengingactivity. The vitamins increased the relative light unit (RLU%) of the system (H2O2/•OH-microperoxidase-luminol)together with magnesium sulfate, zinc sulfate and zincgluconate solutions, while decreased free radical formationtogether with magnesium gluconate, manganese sulfate andmanganese gluconate solutions (Table 3). According to the results it has been stated that chemi-luminescence measurement is an efficient method for thedetermination of free radical generating or scavengingactivity of metal compounds as well.AcknowledgmentsThis work was supported by the National Research andDevelopment Program 1/047/2001.ReferencesBlázovics A, Kovács Á, Lugasi A, Hagymási K, Bíró L, Fehér J (1999)Antioxidant defence in erythrocytes and plasma of patients with activeand quiescent Crohn’s disease and ulcerative colitis: A chemilumi-nescent study. Clin Chem 45:895-896.Ebadi M, Leuschen MP, Refaey H, Hamada F M, Rojas P (1996) Theantioxidant properties of zinc and metallothionein. Neurochem Int29:159-166.Fenton HJH (1894) Oxidation of tartaric acid in presence of iron. J ChemSoc 65:899-910.Fox C, Ramsoomair D, Carter C (2001) Magnesium: its proven andpotential clinical significance. Southern Med J 94:1195-1201.Goldstein S, Meyerstein D, Czapski G (1993) The Fenton reagents. FreeRad Biol Med 15:435-445.Haber F, Willstätter R (1931) Unpairedness and radical chains in thereaction mechanism of organic and enzymic process. Ber DeutschChem Ges 64:2844-2856.Haber F, Weiss J (1934) The catalytic decomposition of hydrogen peroxideby iron salts. Proc Roy Soc London, 147:332-351.Hallberg L, Harwerth HG, Vanotti A eds., (1970) Iron deficiency:pathogenesis, clinical aspects, therapy. Academic Press, London, NewYork, 1-628.Table 1. Free radical generating or scavenging abilities ofmetal compounds (RLU %) and standard deviation (SD %) inthe H2O2 /•OH- luminol system.Samples RLU % SD %Background int 100Magnesium oxi 125 1.2Magnesium chl 71.0 0.8Magnesium sul 20.6 0.4Magnesium cit 5.1 1.0Magnesium glu 125 1.1Manganese dic 26.8 1.3Manganese sul 12.5 0.3Manganese glu 102 1.5Zinc chloride 4.9 0.6Zinc sulfate 6.6 0.2Zinc citrate 13.5 1.7Zinc gluconate 6.0 1.4Vitamin E and C 15.6 0.5Table 2. Free radical generating or scavenging abilities ofmetal compounds (RLU %) and standard deviation (SD %) inthe H2O2 /•OH- microperoxidase-luminol system.Samples RLU % SD %Background int 100Magnesium oxi 177.4 0.9Magnesium chl 104.7 0.9Magnesium sul 106 0.3Magnesium cit 2.3 2.5Magnesium glu 388 4.9Manganese dic 364 2.5Manganese sul 366 0.4Manganese glu 203 3.0Zinc chloride 201.6 1.1Zinc sulfate 82.6 0.1Zinc citrate 74.3 3.6Zinc gluconate 82.1 6.6Vitamin E and 91.6 0.4Table 3. Free radical generating or scavenging abilities ofmetal compounds in the presence of Vitamin E and C (RLU %)and standard deviation (SD %) in the H2O2 /•OH-microperoxidase-luminol systemSamples RLU % SD %Background intensity 100Magnesium sulfate 191.5 1.2Magnesium gluconate 182.9 0.8Manganese sulfate 240 0.3Manganese gluconate 160.5 0.4Zinc sulfate 95.9 0.1Zinc gluconate 94.4 0.4109Metal compounds and free radicalsHalliwell B, Gutteridge JMC (1990) Role of free radicals and catalyticmetal ions in human disease: an overview. Meth Enzymol 86:1-85.Kaltwasser JP, Werner E, Niechzial M (1987) Bioavailability and thera-peutic efficacy of bivalent and trivalent iron preparations. Arz-ForschDrug Res 37:122-129.Rauch P, Kas J, Ranny M (1990) iron bioavailability from its complex withsucrose. Food Chem 36:129-134.Sigel A, Sigel H (1999) Interactions Between Free Radicals and Metal Ionsin Life Process. In Sigel A, Sigel H eds., Metal Ions in BiologicalSystems. Marcel Dekker Inc, New York, Basel, 36:1-797.Szentmihályi K, Lakatos B, Sándor Z, Hajdú M, Vinkler P (1998) Prepa-ration of magnesium polygalacturonate complexes for magne-siumsupplementation and their physicochemical characterization. In KissAS ed., Magnesium. Magnesium and Interaction of Magnesium withTrace Elements. Hungarian Chemical Society, Budapest, 241-244.Tampo Y, Yonaha M (1992) Antioxidant mechanism of manganese (II) inphospholipid peroxidation. Free Radical Biol Med 13:115-120.Zidenberger-Cherr S, Keen CL (1991) Essential trace elements in antiox-idant processes. In Dreosti IE ed., Trace Elements, Micro Nutrients,and Free Radicals. Humana Press, Totowa, New Jersey, 107-127.

Free radical properties of metal complexes

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Free radical properties of metal complexes

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