Cláudia Vargas Klimaczewski

Antiulcerogenic activity of Scutia buxifolia on gastric ulcers induced by ethanol in rats

Gastric ulcers affect many people around the world and their development is a result of the imbalance between aggressive and protective factors in the gastric mucosa. Scutia buxifolia, commonly known as coronilha, has attracted the interest of the scientific community due to its pharmacological properties and its potential therapeutic applications. In this study, the preventive effects of the crude extract of Scutia buxifolia (ceSb) against gastric ulcer induced by 70% ethanol were evaluated in male Wistar rats. In addition, the composition of ceSb was clarified by high-performance liquid chromatography (HPLC). S. buxifolia extract (100, 200 and 400 mg/kg body weight) attenuated oxidative and histopathological features induced by ethanol. Moreover, all evaluated doses of ceSb caused significant (P<0.001 and P<0.0001) and dose-dependent increase in sulfhydryl groups (NPSH) levels, catalase (CAT) and superoxide dismutase (SOD) activities. Furthermore, the administration of ceSb reversed the increase in lipid peroxidation produced by ethanol. The protective effect of the extract could be attributed to antioxidant compounds present in the ceSb, such as flavonoids and phenolic acids, which were quantified by HPLC. Thus, an antioxidant effect of the extract leads to a protection on gastric tissue. These results indicate that S. buxifolia could have a beneficial role against ethanol toxicity by preventing oxidative stress and gastric tissue injury.

Influence of diphenyl diselenide on chlorpyrifos-induced toxicity in Drosophila melanogaster

Exposure to chlorpyrifos (CPF) poses several harmful effects to human and animal health. The present study investigated the influence of diphenyl diselenide (DPDS) on CPF-induced toxicity in Drosophila melanogaster. Firstly, the time course lethality response of virgin flies (2- to 3-day-old) to CPF (0.075-0.6μg/g) and DPDP (5-40μmol/kg) in the diet for 28 consecutive days were investigated. Subsequently, the protective effect of DPDS (10, 20 and 40μmol/kg) on CPF (0.15μg/g)-induced mortality, locomotor deficits, neurotoxicity and oxidative stress was assessed in a co-exposure paradigm for 7 days. Results showed that CPF exposure significantly decreased the percent live flies in a time- and concentration-dependent manner, whereas the percent live flies with DPDS treatment was not statistically different from control following 28 days of treatment. In the co-exposure study, CPF significantly increased flies mortality while the survivors exhibited significant locomotor deficits with decreased acetylcholinesterase (AChE) activity. Dietary supplementation with DPDS was associated with marked decrease in mortality, improvement in locomotor activity and restoration of AChE activity in CPF-exposed flies. Moreover, CPF exposure significantly decreased catalase and glutathione-S-transferase activities, total thiol level with concomitant significant elevation in the levels of reactive oxygen species and thiobarbituric acid reactive substances in the head and body regions of the treated flies. Dietary supplementation with DPDS significantly improved the antioxidant status and prevented CPF-induced oxidative stress, thus demonstrating the protective effect of DPDS in CPF-treated flies.

Antioxidant properties of diorganoyl diselenides and ditellurides: modulation by organic aryl or naphthyl moiety

Diorganoyl dichalcogenide compouds can have antioxidant activity in different in vitro and in vivo models. Here, we have compared the potential antioxidant activity of 1-dinaphthyl diselenide (1-NapSe)2, 2-dinaphthyl diselenide (2-NapSe)2, 1-dinaphthyl distelluride (1-NapTe)2, 2-dinaphthyl ditelluride (2-NapTe)2 with their well-studied analogs diphenyl diselenide ((PhSe)2) and diphenyl telluride ((PhTe)2). (PhSe)2, (PhTe)2, and naphthalene analogs-inhibited Fe(II)-induced lipid peroxidation, catalytically decomposed hydrogen peroxide and oxidized thiols, such as dithiothreitol (DTT), Cysteine (CYS), dimercaptopropionic acid (DMPS), and thiophenol (PhSH). (PhSe)2 was the less potent of the tested compounds against Fe(II)-induced lipid peroxidation in brain homogenates and the change in the organic moiety from an aryl to naphthyl group increased considerably the antioxidant potency of diselenide compounds. However, the change from aryl to naphthyl had little effect on the thio-peroxidase-like activity of diorganoyl dichalcogenides. These results suggest that minor changes in the organic moiety of aromatic diselenide compounds can modify profoundly their capacity to inhibit iron-induced lipid peroxidation. The pharmacological properties of organochalcogens are thought to be linked to their capacity of modulating oxidative stress. Consequently, it becomes important to explore the toxicological properties of dinaphthyl diselenides and ditellurides.

Parkia biglobosa Improves Mitochondrial Functioning and Protects against Neurotoxic Agents in Rat Brain Hippocampal Slices

Objective. Methanolic leaf extracts of Parkia biglobosa, PBE, and one of its major polyphenolic constituents, catechin, were investigated for their protective effects against neurotoxicity induced by different agents on rat brain hippocampal slices and isolated mitochondria. Methods. Hippocampal slices were preincubated with PBE (25, 50, 100, or 200 µg/mL) or catechin (1, 5, or 10 µg/mL) for 30 min followed by further incubation with 300 µM H2O2, 300 µM SNP, or 200 µM PbCl2 for 1 h. Effects of PBE and catechin on SNP- or CaCl2-induced brain mitochondrial ROS formation and mitochondrial membrane potential (ΔΨm) were also determined. Results. PBE and catechin decreased basal ROS generation in slices and blunted the prooxidant effects of neurotoxicants on membrane lipid peroxidation and nonprotein thiol contents. PBE rescued hippocampal cellular viability from SNP damage and caused a significant boost in hippocampus Na+, K+-ATPase activity but with no effect on the acetylcholinesterase activity. Both PBE and catechin also mitigated SNP- or CaCl2-dependent mitochondrial ROS generation. Measurement by safranine fluorescence however showed that the mild depolarization of the ΔΨm by PBE was independent of catechin. Conclusion. The results suggest that the neuroprotective effect of PBE is dependent on its constituent antioxidants and mild mitochondrial depolarization propensity.

Effect of Syzygium cumini and Bauhinia forficata aqueous-leaf extracts on oxidative and mitochondrial parameters in vitro.

Aqueous-leaf extract of Syzygium cumini and Bauhinia forficata are traditionally used in the treatment of diabetes and cancer, especially in South America, Africa, and Asia. In this study, we analyzed the effects of these extracts on oxidative and mitochondrial parameters in vitro, as well as their protective activities against toxic agents. Phytochemical screenings of the extracts were carried out by HPLC analysis. The in vitro antioxidant capacities were compared by DPPH radical scavenging and Fe2+ chelating activities. Mitochondrial parameters observed were swelling, lipid peroxidation and dehydrogenase activity. The major chemical constituent of S. cumini was rutin. In B. forficata were predominant quercetin and gallic acid. S. cumini reduced DPPH radical more than B. forficata, and showed iron chelating activity at all tested concentrations, while B. forficata had not similar property. In mitochondria, high concentrations of B. forficata alone induced a decrease in mitochondrial dehydrogenase activity, but low concentrations of this extract prevented the effect induced by Fe2++H2O2. This was also observed with high concentrations of S. cumini. Both extracts partially prevented the lipid peroxidation induced by Fe2+/citrate. S. cumini was effective against mitochondrial swelling induced by Ca2+, while B. forficata alone induced swelling more than Ca2+. This study suggests that leaf extract of S. cumini might represent a useful therapeutic for the treatment of diseases related with mitochondrial dysfunctions. On the other hand, the consumption of B. forficata should be avoided because mitochondrial damages were observed, and this possibly may pose risk to human health.

Peumus boldus attenuates copper-induced toxicity in Drosophila melanogaster

Peumus boldus (P. boldus) is a medicinal plant popularly used in the treatment of gastrointestinal disorders. P. boldus aqueous extract is rich in phenolic compounds and alkaloids that possess antiinflammatory and antioxidant effects. In the present study, the potential protective effect of P. boldus against Cu2+-induced toxicity was investigated. Adult Drosophila melanogaster were exposed to Cu2+ (1mM and 3mM) and/or P. boldus aqueous extract (5mg/mL) in the food during 4days. Cu2+-fed flies had impairment in the negative geotaxis performance (i.e. motor climbing capability) as well as a higher incidence of mortality when compared to the control group. P. boldus co-treatment afforded protection against the Cu2+-induced toxicity. Acetylcholinesterase (AChE) and glutathione S-transferase (GST) activity decreased significantly in D. melanogaster after Cu2+ exposure. P. boldus co-exposure for 4days restored enzyme activities to control levels. In addition, Cu2+ exposure caused a significant increase in the mRNA levels of antioxidant enzymes, superoxide dismutase (Sod1), catalase (Cat), thioredoxin reductase (TrxR1) and nuclear factor erythroid 2-related factor 2 (Nrf2), as well as increased the mRNA levels of acetylcholinesterase (Ace). The expression of P-type ATPase (Atp7A) and copper uptake protein 1 (Ctr1A) mRNAs were up-regulated in D. melanogaster exposed to Cu2+. The co-treatment with P. boldus blunted Cu2+-induced up-regulation of Atp7A and down-regulated Ctr1A mRNA expression. These findings suggest that P. boldus extracts reduce Cu2+-induced toxicity but not Cu2+ absorption in D. melanogaster. Consequently, P. boldus can be a potential therapeutical alternative for modulating Cu2+-associated toxicity.

Ascorbic acid oxidation of thiol groups from dithiotreitol is mediated by its conversion to dehydroascorbic acid.

The aim of the present study was to investigate whether the in vitro pro-oxidant effect of ascorbic acid towards thiol groups could be mediated by free radicals formed during its auto-oxidation and/or by a direct oxidation of -SH groups by its oxidized form (dehydroascorbic acid). This hypothesis was examined by measuring the rate of AA (ascorbic acid) oxidation in MOPS (3-morpholinepropanesulfonic acid buffer) and phosphate buffer (PB). Here we have used dithiothreitol (DTT) as model of vicinal thiol-containing enzymes, namely δ-aminolevulinate dehydratase. The rate of AA and DTT oxidation was more pronounced in the presence of PB than in the MOPS. AA oxidation induced by iron/EDTA complex was significantly reduced by addition of superoxide dismutase, catalase and DTT to the reaction medium. H2O2 alone did not stimulate the oxidation of AA; however, AA oxidation was enhanced significantly with the addition of crescent concentrations of iron. Conversely, in DTT oxidation assay (without AA) the addition of iron, EDTA and H2O2, did not promote the oxidation of -SH groups. Our findings suggest that in the presence of physiological concentrations of AA and thiols, the oxidation of -SH groups is mediated by AA conversion to dehydroascorbic acid with the participation of iron. Furthermore, free radical species formed during the auto-oxidation of AA apparently did not oxidize thiol groups to a significant extent.

Interaction of metals from group 10 (Ni, Pd, and Pt) and 11 (Cu, Ag, and Au) with human blood δ-ALA-D: in vitro and in silico studies

Mammalian δ-aminolevulinate dehydratase (δ-ALA-D) is a metalloenzyme, which requires Zn(II) and reduced thiol groups for catalytic activity, and is an important molecular target for the widespread environmental toxic metals. The δ-ALA-D inhibition mechanism by metals of Group 10 (Ni, Pd, and Pt) and 11 (Cu, Ag, and Au) of the periodic table has not yet been determined. The objective of this study was to characterize the molecular mechanism of δ-ALA-D inhibition caused by the elements of groups 10 and 11 using in vitro (δ-ALA-D activity from human erythrocytes) and in silico (docking simulations) methods. Our results showed that Ni(II) and Pd(II) caused a small inhibition (~ 10%) of the δ-ALA-D. Pt(II) and Pt(IV) significantly inhibited the enzyme (75% and 44%, respectively), but this inhibition was attenuated by Zn(II) and dithiothreitol (DTT). In group 11, all metals inhibited δ-ALA-D with great potency (~ 70–90%). In the presence of Zn(II) and DTT, the enzyme activity was restored to the control levels. The in silico molecular docking data suggest that the coordination of the ions Pt(II), Pt(IV), Cu(II), Ag(I), and Au(III) with thiolates groups from C135 and C143 residues from the δ-ALA-D active site are crucial to the enzyme inhibition. The results indicate that a possible mechanism of inhibition of δ-ALA-D by these metals may involve the replacement of the Zn(II) from the active site and/or the cysteinyl residue oxidation.