Selenium distribution in ryegrass and its antioxidant role as affected by sulfur fertilization

Selenium (Se) essentiality to plants has not been demonstrated although evidence indicates that it plays a significant role as antioxidant in higher plants. Research concerning to the uptake and allocation of Se in plant tissues is reported in numerous works. However, the effect of sulfur (S) on both the distribution and the antioxidant ability of Se in selenite-treated plant remains unclear. In this work the effect of S application (0–100 mg S kg⁻¹ soil) on shoot Se concentration of Lolium perenne cv. Aries was studied. Se distribution into different fractions of plants supplied with selenite (2 mg Se kg⁻¹ soil) and the state of the antioxidative system were determined. Results showed that shoot Se concentration decreased at least 33% by S application. Plants supplied with S registered the lowest GSH-Px activity and the highest lipid peroxidation. Most of Se was incorporated into the organic fraction of the plant tissue irrespective of the S treatment. However, a significant decrease of both the soluble protein and the amino acid fraction occurred, and the residual Se fraction seemed to increase at expense of the organic-Se soluble fraction. Although no essential selenoproteins have been clearly identified in vascular plants, the decrease of the soluble protein fraction and the different pattern of protein synthesized (SDS-PAGE analysis) may explain the observed reduction of the GSH-Px activity.     

Design and biological activity of imidazole-containing peptidomimetics with a broad-spectrum antioxidant activity

Histidine-containing natural dipeptides, such as L-carnosine, were reported to be effective against different oxygen-derived free radicals, and also lipoperoxyl radicals. However, L-carnosine appeared to be uneffective in vivo, due to the presence of ubiquitous specific or semi-specific hydrolytic enzymes. Therefore, a series of peptidomimetics were synthesized in order to confer resistance to enzymatic hydrolysis. Some structural modifications were also done in an attempt to improve the antioxidant power of the molecule, for example, in relation to binding of ferrous ions. The following methods were used for the evaluation of peptidomimetics:– The resistance to enzymatic deactivation was determined using either a purified specific enzyme or a multi-enzymatic system.– The free radical scavenging potential was measured by different in vitro methods involving different free radical species and biological targets.– Deactivation of lipid hydroperoxides was monitored by HPLC and protection of membrane phospholipids and proteins was demonstrated.– The effectiveness of peptidomimetics in vivo was evaluated.It was shown that decarboxylation of L-carnosine results in an important improvement of the resistance towards hydrolytic enzymes. In vitro experiments have demonstrated, for a series of peptidomimetics, free radical scavenging and lipid hydroperoxide deactivating properties similar to or even better than the natural peptide (depending on the experimental design). In addition, the two peptidomimetics -alanylhistamine and L-prolylhistamine proved to be far superior in inhibiting the lipid hydroperoxide-mediated cross-linking of a representative protein. Finally, -alanylhistamine was able to protect skin enzymes from UV-induced degradation in vivo.     

Synthesis and biological activity of halophenols as potent antioxidant and cytoprotective agents

A series of new bromophenols and chlorophenols were prepared by a practical route. The in vitro antioxidative activity of the halophenols was evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay, and their cytoprotective activity was also tested on hydrogen peroxide (H₂O₂)-induced injury in human umbilical vein endothelial cells (HUVEC). All halophenols tested displayed moderate to good DPPH radical-scavenging activity, and two bromophenols, 2,3′-dibromo-4,5,6′-trihydroxydiphenylmethanone (16c) and 2,3-dibromo-4,5-dihydroxydiphenylmethanone (17c) exhibited high protective activity against H₂O₂-induced injury in HUVEC with EC₅₀ values of 0.4 and 0.8 μM, respectively. The preliminary structure–activity relationships of these compounds were also investigated in order to determine the essential structures required for their bioactivities.     

UVB photoprotective role of mycosporines in yeast: photostability and antioxidant activity of mycosporine-glutaminol-glucoside

Several yeast species are able to synthesize and accumulate UV-radiation-absorbing mycosporine metabolites that are of unclear physiological function. In this work we analyzed the relationship between mycosporine-glutaminol glucoside (MGG) production, cell survival after UVB irradiation, and formation of cyclobutane pyrimidine dimers (CPDs). We also assessed the photostability and singlet oxygen quenching activity of MGG. A set of nine isolates of the basidiomycetous yeast Cryptococcus steppossus cultured in both dark and light conditions was used for the studies. Survival of the UVB-irradiated isolates and MGG concentration had a linear relationship when the concentration was over 2.5 mg g(-1). CPD accumulation and MGG accumulation were inversely related. MGG in aqueous solution was photostable with a photodecomposition quantum yield of 1.16 × 10(-5). MGG quenching of singlet oxygen was also observed, and the rate constant for the process in D(2)O was 5.9 × 10(7) M(-1) s(-1). Our results support the idea that MGG plays an important role as a UVB photoprotective metabolite in yeasts by protecting against direct damage on DNA and probably against indirect damage by singlet oxygen quenching.     

On-line antioxidant activity determination: comparison of hydrophilic and lipophilic antioxidant activity using the ABTS*+ assay

The ABTS/H(2)O(2)/HRP decoloration method is capable of determining both hydrophilic (in buffered media) and lipophilic (in organic media) antioxidant properties in complex samples. Now, we have adapted this method for on-line chromatographic determination. The easy, rapid and controlled generation of the ABTS radical and its great stability in buffered and organic media were important characteristics in the measurement of antioxidant activities. The HPLC-ABTS method used two pumps (one for isocratic eluting-phase and the other for preformed ABTS radical) and an UV-VIS diode array detector. The dual analysis of samples -- conventional (with UV-VIS detection) and ABTS-scavenging (at 600 nm) -- provided valuable on-line information about the correspondence between the presence of a determined compound and its possible antioxidant activity, and was applicable to both hydrophilic and lipophilic antioxidants (HAA and LAA). A comparison between HAA and LAA determined by the end-point method and by the on-line HPLC method is presented. The application to juices showed that both methods are suitable, sensitive and selective, gave similar values, and the HPLC-ABTS method contributed additional information about the antioxidant activity profile.     

Gas exchange, growth, and antioxidant activity in sugarcane under biological nitrogen fixation

The aim of this study was to characterize the key physiological aspects of three sugarcane cultivars (RB92579, RB867515 and RB872552) under biological nitrogen fixation (BNF). Plants were generated in tubes containing aseptic substrates and these plants were transferred to pots containing washed sand, but watered with a mineral fertilizer, and inoculated with a mixture of five diazotrophic bacteria three times at seven-day intervals. Under BNF, all of the cultivars contained half of their total leaf nitrogen content and 50% less shoot dry mass. The leaves of plants under BNF showed approximately 65% less of the total protein content (TP). The gas-exchange control plants had twice the CO₂ assimilation rates than the BNF plants. The activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) was increased in all cultivars under BNF when compared with the control; thus, the content of hydrogen peroxide (H₂O₂) was also increased in these plants. The results of this study indicate that after acclimatization, the inoculation of young plants from tissue culture with diazotrophic bacteria could supply approximately 50% of their nitrogen requirement.     

Selenium and antioxidant vitamin and lipidoperoxidation levels in preaging French population

Selenium (Se) and antioxidant vitamins might play an important role in the etiology of free radical-related diseases and aging. In the édude de vieillissement artériel (EVA) study, we have determined the plasma thiobarbituric acid reacting substances (TBARS) as an indicator of free radical-induced lipid peroxidation, plasma selenium and carotenoids, and erythrocyte vitamin E levels in 1389 subjects aged 59–71 years. We also looked for an association between these parameters and cardiovascular risk factors in early elderly. The results show that plasma TBARS were significantly increased in elderly in comparison with values reported in younger adults. However, plasma Se and carotenoids as well as erythrocyte vitamin E in elderly people are close to those reported in adult people. If plasma Se showed no difference between men and women, the three other parameters were significantly higher in women than in men. With regard with cardiovascular risk factors, plasma TBARS were highly positively correlated with total and low-density lipoprotein (LDL) cholesterol in men and women. Plasma carotenoids were also positively correlated with plasma total cholesterol and LDL cholesterol in both sexes. Finally, plasma TBARS were highly correlated with smoking and alcohol consumption. In conclusion, this part of the EVA study shows that some cardiovascular risk factors, like smoking and cholesterol level, are associated with high free radical-induced TBARS levels in the preaging population, although plasma Se and carotenoids as well as erythrocyte vitamin E levels in elderly people were close to those reported in adult younger people.     

Mucolytics and antioxidant activity

We investigated effects of the mucolytics ambroxol and N-acetylcysteine on airways reactivity evoked by histamine in guinea pigs exposed to toluene vapors. We did not find significant changes in reactivity of tracheal smooth muscle from animals treated with mucolytics compared to the control group. However, the administration of ambroxol and N-acetylcysteine caused a significant decrease in lung tissue reactivity. The effect of ambroxol was more pronounced after intraperitoneal injection than after inhalation, while N-acetylcysteine was only effective after inhalation. The protective effects of mucolytics in the lung tissue may be due to their antioxidant activity together with other mechanisms.     

Mitochondrial creatine kinase activity prevents reactive oxygen species generation: antioxidant role of mitochondrial kinase-dependent ADP re-cycling activity

As recently demonstrated by our group (da-Silva, W. S., Gómez-Puyou, A., Gómez-Puyou, M. T., Moreno-Sanchez, R., De Felice, F. G., de Meis, L., Oliveira, M. F., and Galina, A. (2004) J. Biol. Chem. 279, 39846-39855) mitochondrial hexokinase activity (mt-HK) plays a preventive antioxidant role because of steady-state ADP re-cycling through the inner mitochondrial membrane in rat brain. In the present work we show that ADP re-cycling accomplished by the mitochondrial creatine kinase (mt-CK) regulates reactive oxygen species (ROS) generation, particularly in high glucose concentrations. Activation of mt-CK by creatine (Cr) and ATP or ADP, induced a state 3-like respiration in isolated brain mitochondria and prevention of H(2)O(2) production obeyed the steady-state kinetics of the enzyme to phosphorylate Cr. The extension of the preventive antioxidant role of mt-CK depended on the phosphocreatine (PCr)/Cr ratio. Rat liver mitochondria, which lack mt-CK activity, only reduced state 4-induced H(2)O(2) generation when 1 order of magnitude more exogenous CK activity was added to the medium. Simulation of hyperglycemic conditions, by the inclusion of glucose 6-phosphate in mitochondria performing 2-deoxyglucose phosphorylation via mt-HK, induced H(2)O(2) production in a Cr-sensitive manner. Simulation of hyperglycemia in embryonic rat brain cortical neurons increased both DeltaPsi(m) and ROS production and both parameters were decreased by the previous inclusion of Cr. Taken together, the results presented here indicate that mitochondrial kinase activity performed a key role as a preventive antioxidant against oxidative stress, reducing mitochondrial ROS generation through an ADP-recycling mechanism.     

Selenium and sulfur in antioxidant protective systems: relationships with vitamin E and malaria.

The metabolic relationships among the antioxidant nutrients selenium, sulfur, and vitamin E are particularly close. Selenium and vitamin E have long been known to spare one another in certain nutritional diseases of animals, and selenium has been considered to have a key antioxidant defense function as a component of glutathione peroxidase. However, the antioxidant role of glutathione peroxidase has been questioned and new proteins containing selenium have been identified: phospholipid hydroperoxide glutathione peroxidase, selenoprotein P, and iodothyronine deiodinase. Glutathione peroxidase activity independent of selenium resides in the glutathione S-transferases. Glutathione participates in both enzymatic and nonenzymatic antioxidant defense systems. Some low-molecular weight selenium compounds (e.g., ebselen) exhibit glutathione peroxidase-like action. Certain low molecular weight thiols decompose peroxides nonenzymatically (e.g., the ovothiols). Murine malaria appears to be a useful experimental model for investigating interrelationships of selenium and vitamin E. Vitamin E deficiency protects against the parasite, especially when the mice are concurrently fed peroxidizable fat such as fish or linseed oils. Selenium deficiency, on the other hand, has little or no protective effect against the parasite. Any practical utility of pro-oxidant diets in combating human malaria remains to be determined.     

Methylglyoxal: metabolism and biological activity

The enzymic formation of methylglyoxal from dihydroxyacetone phosphate and aminoacetone (metabolites of carbohydrates and proteins) is considered. Methylglyoxal transformation into lactic and pyruvic acids is related to energy metabolism, catabolism and anabolism dissociation processes in carbohydrates and proteins, and, probably, to maintenance of asymmetrical entropy in vivo on the constant level. Attention is paid to the methylglyoxal inhibition of enzymes, its interaction with glutathione and polyamines affecting the mechanisms regulating protein synthesis and cellular division. The methods for obtaining and quantitative determination of methylglyoxal are described.     

Synthesis and antitumor activity of novel amsacrine analogs: The critical role of the acridine moiety in determining their biological activity

A new series of N-[4-(2′-oxo-2H-pyrano[2,3-b]quinolin-5′-ylamino)-phenyl]-methanesulfonamides was prepared and analyzed as novel amsacrine-like derivatives. Our preliminary biological evaluation has shown that the replacement of the acridine moiety with the analogous 2-oxo-2H-pyrano[2,3-b]quinoline system drastically reduced both their anticancer activity and their propency to intercalate into double stranded DNA.     

Neem oil nanoemulsions: characterisation and antioxidant activity

The aim of the present work is to develop nanoemulsions (NEs), nanosized emulsions, manufactured for improving the delivery of active pharmaceutical ingredients. In particular, nanoemulsions composed of Neem seed oil, contain rich bioactive components, and Tween 20 as nonionic surfactant were prepared. A mean droplet size ranging from 10 to 100?nm was obtained by modulating the oil/surfactant ratio. Physicochemical characterisation was carried out evaluating size, ζ-potential, microviscosity, polarity and turbidity of the external shell and morphology, along with stability in simulated cerebrospinal fluid (CSF), activity of Neem oil alone and in NEs, HEp-2 cell interaction and cytotoxicity studies. This study confirms the formation of NEs by Tween 20 and Neem oil at different weight ratios with small and homogenous dimensions. The antioxidant activity of Neem oil alone and in NEs was comparable, whereas its cytotoxicity was strongly reduced when loaded in NEs after interaction with HEp-2 cells.     

The role of bitoxibacillin components in the manifestation of its biological activity

New methods were developed and applied to quantitative determination of beta-exotoxin and antibiotic activity of delta-endotoxin with respect to Micrococcus spp. in bitoxibacillin (BTB) and the fermentation broths prepared under industrial conditions. The biosynthesis of beta-exotoxin in the period of its maximum accumulation during the fermentation was estimated. It was shown that the primary biological effect of BTB on insects consisted in the actions of beta-exotoxin and delta-endotoxin. Biological activity of each of the entomocidal components of the entomocidal components of BTB did not practically correlated with the number of viable spores. There was a correlation between the antibiotic activity of crystalline B. thuringiensis subsp. thuringiensis solutions and the insecticidal activity of the entomopathogenic preparations. Determination of beta-exotoxin and antibiotic activity of delta-endotoxin might be used as a complex procedure for testing the quality of BTB. The method for estimating antibiotic activity of the crystal solutions allowed one to assay the biological activity of other preparations based on Bacillus thuringiensis non-synthesizing beta-exotoxin.