Vanadocene arsenate complexes: evidence of super-hyperfine coupling with (75)As

The reaction of vanadocene dichloride with sodium arsenate gives Cp(2)V(O(2)AsO(2)H). This compound was identified on the basis of the super-hyperfine coupling observed in the solution EPR spectrum. The effect of substitution was studied on the ring-substituted and ansa-bridged compounds.

Mechanism of the antioxidant action of silybin and 2,3-dehydrosilybin flavonolignans: a joint experimental and theoretical study

Flavonolignans from silymarin, the standardized plant extract obtained from thistle, exhibit various antioxidant activities, which correlate with the other biological and therapeutic properties of that extract. To highlight the mode of action of flavonolignans as free radical scavengers and antioxidants, 10 flavonolignans, selectively methylated at different positions, were tested in vitro for their capacity to scavenge radicals (DPPH and superoxide) and to inhibit the lipid peroxidation induced on microsome membranes. The results are rationalized on the basis of (i) the oxidation potentials experimentally obtained by cyclic voltammetry and (ii) the theoretical redox properties obtained by quantum-chemical calculations (using a polarizable continuum model (PCM)-density functional theory (DFT) approach) of the ionization potentials and the O-H bond dissociation enthalpies (BDEs) of each OH group of the 10 compounds. We clearly establish the importance of the 3-OH and 20-OH groups as H donors, in the presence of the 2,3 double bond and the catechol moiety in the E-ring, respectively. For silybin derivatives (i.e., in the absence of the 2,3 double bond), secondary mechanisms (i.e., electron transfer (ET) mechanism and adduct formation with radicals) could become more important (or predominant) as the active sites for H atom transfer (HAT) mechanism are much less effective (high BDEs).

Nitric oxide sensor based on carbon fiber covered with nickel porphyrin layer deposited using optimized electropolymerization procedure

Electropolymerization regime of meso-tetrakis(3-methoxy-4-hydroxyphenyl) porphyrin is optimized to yield films possessing both electrocatalytical and permselective properties towards nitric oxide oxidation. The sensor composed of electrochemically oxidized carbon fiber, covered solely with nickel porphyrin derivative layer electropolymerized using our method, is characterized by high selectivity towards nitrite (1:600), ascorbate (1:8000) and dopamine (>1:80), determined by constant potential amperometry at 830 mV (vs. Ag/AgCl). Selectivity for ascorbate and dopamine as well as detection limit for NO (1.5 nM at S/N=3) is 5-10 times better than parameters usually reported for Nafion coated porphyrinic sensors. Nafion coating can further enhance selectivity properties as well as aids to the stability of the sensors' responses.

Catalytic reaction of cytokinin dehydrogenase: preference for quinones as electron acceptors

The catalytic reaction of cytokinin oxidase/dehydrogenase (EC 1.5.99.12) was studied in detail using the recombinant flavoenzyme from maize. Determination of the redox potential of the covalently linked flavin cofactor revealed a relatively high potential dictating the type of electron acceptor that can be used by the enzyme. Using 2,6-dichlorophenol indophenol, 2,3-dimethoxy-5-methyl-1,4-benzoquinone or 1,4-naphthoquinone as electron acceptor, turnover rates with N6-(2-isopentenyl)adenine of approx. 150 s(-1) could be obtained. This suggests that the natural electron acceptor of the enzyme is quite probably a p-quinone or similar compound. By using the stopped-flow technique, it was found that the enzyme is rapidly reduced by N6-(2-isopentenyl)adenine (k(red)=950 s(-1)). Re-oxidation of the reduced enzyme by molecular oxygen is too slow to be of physiological relevance, confirming its classification as a dehydrogenase. Furthermore, it was established for the first time that the enzyme is capable of degrading aromatic cytokinins, although at low reaction rates. As a result, the enzyme displays a dual catalytic mode for oxidative degradation of cytokinins: a low-rate and low-substrate specificity reaction with oxygen as the electron acceptor, and high activity and strict specificity for isopentenyladenine and analogous cytokinins with some specific electron acceptors.

Chemoprotective effect of plant phenolics against anthracycline-induced toxicity on rat cardiomyocytes. Part III. Apigenin, baicalelin, kaempherol, luteolin and quercetin

Flavonoids are found universally in plants and act as free radical scavenging and chelating agents with antiinflammatory, antiischemic, vasodilating and chemoprotective properties. In this study, the antilipoperoxidative and cytoprotective effects of apigenin, baicalein, kaempferol, luteolin and quercetin against doxorubicin-induced oxidative stress were investigated in isolated rat heart cardiac myocytes, mitochondria and microsomes. After preincubation of cardiomyocytes with the test compounds for 1 h the cardiomyocytes were treated with the toxic agent, doxorubicin (100 micro M for 8 h). Cardiomyocyte protection was assessed by extracellular LDH and cellular ADP and ATP production. Cytoprotection was concentration dependent for baicalein > luteolin congruent with apigenin > quercetin > kaempferol. All test compounds had signi fi cantly better protective effects than dexrazoxan, an agent currently used for adjuvant therapy during anthracycline antibiotic therapy. In microsomes/mitochondria the IC(50) values of lipid peroxidation inhibition for quercetin, baicalein, kaempferol, luteolin, and apigenin were 3.1 +/- 0.2/8.2 +/- 0.6, 3.3 +/- 0.3/9.6 +/- 0.5, 3.9 +/- 0.3/10.1 +/- 0.8, 22.9 +/- 1.7/18.2 +/- 0.7, and 338.8 +/- 23.1/73.1 +/- 6.4 mM, respectively. The antilipoperoxidative activity of apigenin differed from its cytoprotective effects, but correlated with the free radical scavenging of 2,2-diphenyl-1-picrylhydrazyl radical and half peak oxidation potential (E(p/2)). Apigenin was the least effective of the flavonoids studied in all models except the cardiomyocyte model where its cardiomyocyte cytoprotective effect was comparable to other compounds.

Sanguinarine is a potent inhibitor of oxidative burst in DMSO-differentiated HL-60 cells by a non-redox mechanism

Sanguinarine (SA), a member of the benzo[c]phenanthridine isoquinoline alkaloids, has been shown to possess antimicrobial, anti-inflammatory, and antioxidant properties. We examined the effects of SA on oxidative burst in DMSO-differentiated HL-60 cells, an excellent model for studying oxidative burst. SA inhibited both N-formyl-Met-Leu-Phe (fMLP) and phorbol 12-myristate 13-acetate (PMA)-induced oxidative burst with half-maximal concentration for inhibition (IC(50)) of 1.5 and 1.8 microM, respectively. Despite suggestions of SA antioxidant activity this inhibition cannot be ascribed to radical scavenging property of SA because the IC(50) for superoxide dismutase-like activity in a non-cellular system was 60 microM. TROLOX, a water-soluble vitamin E analog, had IC(50) of 3 microM in the same system. Moreover, cyclic voltammetry measurements show that SA is not an easily oxidizable species, with a peak anodic potential at 700 mV, as compared to TROLOX with peak anodic potential at 200 mV. On the other hand, TROLOX, when used in cell suspension, was much poorer inhibitor of oxidative burst than SA. When testing direct effect of SA on NADPH oxidase in the post-granular fraction of disrupted cells, the IC(50) was found to be 8.3 microM. It is higher than that observed in whole cells, however, the shift may be ascribed to SDS effect on SA activity. We conclude the SA inhibition of oxidative burst is not caused by SA redox activity but most likely is a result of SA affecting the activity of NADPH oxidase directly and in part by preventing the formation of NADPH oxidase protein complex.

The occurrence of reactive oxygen species in the semen of males from infertile couples

The aim of this pilot study was to establish a reactive oxygen species (ROS) evaluation method as a step in the routine diagnosis of men from infertile couples, which attend the Centre of Assisted Reproduction at the Teaching Hospital in Olomouc. Standard semen analyses were performed manually according to WHO guidelines. The number of peroxidase-positive leukocytes in the semen was determined using the Endtz test. The levels of ROS were estimated by chemiluminescence assay using luminol (5-amino-2,3 dihydro-1,4 phthalazinedione) as a probe. The semen samples were collected from 68 patients. Normospermia was found in 15 patients (22.1 %). The semen samples of 3 normospermic patients were classified as ROS-positive. Elevated ROS production was recorded in all subgroups of patients irrespective of any pathology found. We confirmed that spermatozoa might be the source of ROS as well as the seminal leukocytes. Apart from the leukocytes, sperm cells with residual cytoplasm and immature spermatozoa are considered to be a major source of ROS. Thus it is suggested that sperm morphology abnormalities should be evaluated more carefully.

The occurrence of reactive oxygen species in the semen of males from infertile couples

The aim of this pilot study was to establish a reactive oxygen species (ROS) evaluation method as a step in the routine diagnosis of men from infertile couples, which attend the Centre of Assisted Reproduction at the Teaching Hospital in Olomouc. Standard semen analyses were performed manually according to WHO guidelines. The number of peroxidase-positive leukocytes in the semen was determined using the Endtz test. The levels of ROS were estimated by chemiluminescence assay using luminol (5-amino-2,3 dihydro-1,4 phthalazinedione) as a probe. The semen samples were collected from 68 patients. Normospermia was found in 15 patients (22.1 %). The semen samples of 3 normospermic patients were classified as ROS-positive. Elevated ROS production was recorded in all subgroups of patients irrespective of any pathology found. We confirmed that spermatozoa might be the source of ROS as well as the seminal leukocytes. Apart from the leukocytes, sperm cells with residual cytoplasm and immature spermatozoa are considered to be a major source of ROS. Thus it is suggested that sperm morphology abnormalities should be evaluated more carefully.

Determination of total antioxidant capacity in plasma by cyclic voltammetry. Two case reports

The cyclic voltammetry (CV) was used for the measurement of the plasma total antioxidant capacity from two types of patients. The first one consisted of 29 volunteers (men aged 18-21 years) who were administered placebo or silymarin at a dose of 858 mg/day. After two months of silymarine administration, CV revealed a statistically significant increase in total antioxidant capacity compared to placebo. No statistically significant changes in TBARS, SH-groups, creatininin, urea, and uric acid concentrations were found. The second group under study comprised 49 patients with chronic renal disease during dialysis therapy. After dialysis, CV revealed a decrease of total antioxidant capacity in the plasma, which was equivalent to a decrease in creatinine, urea and uric acid. CV was performed using a system consisting of a working glassy carbon electrode, an auxiliary platinum electrode, and a reference saturated calomel electrode; a linear change of voltage of 200 mV/s was applied. CV is a simple and relatively reliable method for assessment of body antioxidant status. It is also time and cost effective.