Aleksandra Kładna

The effect of thymol and its derivatives on reactions generating reactive oxygen species.

The effects of thymol (TOH), thymoquinone (TQ) and dithymoquinone (TQ2) on the reactions generating reactive oxygen species (ROS) such as superoxide anion radical (O2*-), hydroxyl radical (HO*) and singlet oxygen (1O2) were tested using the chemiluminescence (CL) and spectrophotometry methods. All tested compounds acted as scavengers of various ROS. The rate constant of 1O2-dimols quenching by thymol was calculated.

Enhancing effect of melatonin on chemiluminescence accompanying decomposition of hydrogen peroxide in the presence of copper

The oxidation of melatonin (MEL) using the Cu(II) + H(2)O(2) + HO(-) (the Fenton-like reaction) system was investigated by chemiluminescence (CL), fluorescence, spectrophotometric, and EPR spin trapping techniques. The reaction exhibits CL in the 400-730 nm region. The light emission from the Fenton-like reaction was greatly enhanced in the presence of MEL and was strongly dependent on its concentration. The spectrum measured with cut-off filters revealed maxima at around 460, 500, 580-590, 640-650, and 690-700 nm. The band at 460 nm may be due to the excited cleavage product, N(1)-acetyl-N(2)-formyl-5-methoxykynuramine, whereas the bands at 500, 580-590, 640-650, and 700 nm were similar to those observed for singlet molecular oxygen ((1)O(2)). The effect of reactive oxygen species (ROS) scavengers on the light emission was studied. The CL was strongly inhibited by the (1)O(2) scavengers in a dose-dependent manner; at concentration 1 mM the potency of (1)O(2) scavenging was 5,5-dimethylcyclohexandione-1,3 > methionine > histidine > hydroquinone. The potency of HO(*) scavenging by thiourea, tryptophan, cysteine at concentration 5 mM was 79-94%, by 1 mM glutathione and trolox 75 and 94%, respectively, and by 10 mM cimetidine 18%. Specific acceptors of O(2)(*)(-) such as p-nitroblue tetrazolium chloride and 4,5-dihydroxy-1,3-benzene disulfonic acid (tiron) at concentration 5 mM decreased the CL by 51 and 95%, respectively, whereas superoxide dismutase (SOD) does not reduce the emission at concentration 2.8 U/ml. At higher concentration SOD substantially enhanced the light emission. Addition of 1360 U/ml catalase and 100 microM desferrioxamine strongly inhibited CL (96 and 90%, respectively). The increased generation of (1)O(2) from the Cu/H(2)O(2) system in the presence of MEL was confirmed using the spectrophotometric method based on the bleaching of p-nitrosodimethylaniline and by trapping experiments with 2,2,6,6-tetramethylpiperidine (TEMP) and subsequent electron paramagnetic (EPR) spectroscopy. These findings suggest the increased production of reactive oxygen species (O(2)(*)(-), HO(*), (1)O(2)) from the Fenton-like reaction in the presence of MEL. This means that the hormone is not able to act as classical chain-breaking antioxidant even at low concentration, and may show clear prooxidant activity at higher concentrations. In addition, long-lived carbonyl product of the MEL transformation in the triplet state can also be toxic by transferring its energy to organelles and causing a photochemical process.

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) × 10(9)  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 H(2)O(2) 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.

Luminescence in the oxidation of isoproterenol by the superoxide anion radical in dimethyl sulfoxide

Chemiluminescence appearing during oxidation of isoproterenol using chemical system involving superoxide anion radical has been studied. Chemiluminescence and fluorescence spectra were measured. The chemiluminescence spectrum was measured with cut‐off filters and revealed bands with maximum at 440, 480, 550, 640 and 700 nm. The bands at 480, 640 and 700 nm were similar to those observed for singlet oxygen. The fluorescence spectrum exhibited maximum at 560 nm. The inhibitory effect of several biologically important compounds known as O2 •‐ HO• and 1O2 scavengers on the light emission was studied. The obtained results indicate that oxidation of isoproterenol by O2 •‐ involves products in the electronically excited states. The data also seem to indicate the protective effect of isoproterenol on the deoxyribose degradation.

Formation of singlet oxygen during farmorubicin oxidation.

The enhanced generation of singlet oxygen (1O2) during oxidation of farmorubicin in the Co(II) + H2O2 system was studied using chemiluminescent, fluorescent and spectrophotometic techniques. The influence of 1O2-quenchers, catalase, superoxide anion radical (O2*-) and hydroxyl radical (HO*) scavengers on the light emission was studied. The spectrophotometric determination of 1O2 was based on bleaching of p-nitrosodimethylaniline caused by an intermediate product of the reaction of 1O2 with imidazole, and was followed by monitoring the decrease in optical density at 440 nm.

Prooxidant action of carazolol in the Fenton-like reaction.

Carazolol [4-(2-hydroxy-3-isopropyl-amino-propoxy)-carbazole], a β(3)-adrenoceptor agonist, is clinically used in the treatment of hypertension, cardiac arrhythmias and angina pectoris. Despite the beneficial effect of the drug, its high dose may contribute to cardiotoxicity. This study was conducted to examine whether carazolol can influence hydroxyl radical formation by a Fenton-like reaction [Co(II) + H(2)O(2) + HO(-)] in the presence of ethylenediaminetetraacetic acid. The oxygen free radicals and singlet oxygen ((1)O(2)) formation was traced by three different assay methods: chemiluminescence (CL), an electron spin resonance (ESR) spin trapping with 2,2,6,6-tetramethyl-4-piperidine and 5,5-dimethyl-1-pyrroline-1-oxide, and spectrophotometric determination of (1)O(2) based on bleaching of p-nitrosodimethylaniline. The effect of hydroxyl radical inhibitors and (1)O(2) quenchers on peroxidation of carazolol was also examined. The results indicated that carazolol enhanced the HO radical and (1)O(2) formation in a Fenton-like reaction.

INHIBITORY EFFECT OF SOME BIOLOGICAL COMPOUNDS ON CATECHOLAMINES PEROXIDATION

The aim of the present study was to investigate the inhibitory effect of a number of biologically important compounds on catecholamines (adrenaline, noradrenaline, dopamine) peroxidation with respect to production of reactive oxygen species, especially hydroxyl radicals. Measurements were done using a chemiluminescence technique, in presence of the Cu(II) + H2O2 system. From the compounds examined (some of them proved to be effective in clinical use) carnosine, myoglobin, cimetidine, methionine, captopril, α‐lipoic acid, glutathione, were strongly effective as antioxidants.