Evaluation of the effects of metformin on antioxidant biomarkers and mineral levels in patients with type II diabetes mellitus: A cross-sectional study.

Diabetes mellitus (DM) and arterial hypertension are considered serious public health problems. Several studies have shown that oxidative stress is usually related to the onset of DM and hypertension, as well their associated complications. Moreover, the levels of some minerals are closely related to the pathophysiology of these diseases. Thus, in this study we aimed to evaluate the effect of metformin on the redox profile and mineral levels in the serum of patients with DM type 2 and hypertension. We also tested the effect of metformin on the viability and redox profile of peripheral blood mononuclear cells (PBMCs) for 24 h. As expected, we found that patients with type 2 DM and hypertension + type 2 DM had higher fasting glucose and triglyceride levels. As groundbreaking research, we found that both patients DM type 2 and Hypertension + DM type 2 had reduced myeloperoxidase (MPO) activity. On the other hand, the levels of total thiols (PSH) and vitamin C were increased. There was no statistical significance for the alterations in mineral levels. In addition, metformin treatment had no cytotoxic effect on PBMCs. Similarly, in patients of both groups, MPO activity was reduced and PSH levels were increased in PBMCs. We have shown that metformin is a drug with a protective effect in patients with DM type 2 against oxidative stress by reducing MPO activity and improving the levels of PSH and antioxidant defenders such as vitamin C. The results of in vitro assays support the antioxidant effect of metformin. Furthermore, we suggest studies to assess the biochemical mechanisms of metformin and how it can be used in a pharmacological therapeutic perspective against oxidative damage.

Toxicological and pharmacological evaluation of Discaria americana Gillies & Hook (Rhamnaceae) in mice

Medicinal plants (e.g. Discaria americana) have been used by populations for centuries. However, popular use is not enough to validate these plants as safe and effective medicinal products. The present study sought to evaluate the acute and subacute toxicity as well as the anxiolytic and antinociceptive effects of D. americana root bark and aerial parts extracts in mice. In acute toxicity studies, mice were treated with single intraperitoneal doses of the aforementioned extracts. Subacute toxicity studies were performed by oral administration of the extracts over 14 days. Anxiolytic studies consisted of the elevated plus maze method, and antinociceptive studies were based on the hot plate test. The LD50 value for D. americana aerial parts extract was established at >500 mg/kg, and for the root bark extract, 400 mg/kg. D. americana aerial parts extract produced anxiolytic (250 mg/kg) and antinociceptive effects (125, 200 and 250 mg/kg). Conversely, D. americana root bark extract showed neither anxiolytic nor antinociceptive effects in mice.

As plantas medicinais (i. e. Discaria americana) têm sido utilizadas pela população por séculos, entretanto, o conhecimento popular não é suficiente para validá-las como medicamentos seguros e/ou efetivos. Assim, o presente estudo teve por objetivo avaliar a toxicidade aguda e subaguda, bem como o efeito ansiolítico e antinociceptivo dos extratos da casca da raiz e das partes aéreas da D. americana em camundongos. A toxicidade aguda foi avaliada pela administração dos extratos, via intraperitoneal. Para o estudo da toxicidade subaguda os animais foram tratados oralmente com os extratos por 14 dias. O efeito ansiolítico dos extratos foi determinado através do modelo do labirinto em cruz elevado e o efeito antinociceptivo, mediante o teste da placa quente. O valor da DL50 para o extrato das partes aéreas da D. americana foi definido como > 500 mg/kg, enquanto que para o extrato da casca da raiz foi estabelecido em 400 mg/kg. O extrato das partes aéreas da D. americana apresentou atividade ansiolítica (250 mg/kg) e antinociceptiva (125, 200 e 250 mg/kg). O extrato da casca da raiz da D. americana não apresentou efeito ansiolítico nem antinociceptivo.

Chromium determination in pharmaceutical grade barium sulfate by solid sampling electrothermal atomic absorption spectrometry with Zeeman-effect background correction.

A procedure for chromium (Cr) determination in pharmaceutical grade barium sulfate by direct solid sampling electrothermal atomic absorption spectrometry (DSS-ET AAS) with Zeeman-effect background correction was developed. Operational conditions for the proposed procedure and the use of citric acid, ammonium phosphate, palladium and magnesium nitrate as chemical modifiers were evaluated. Pyrolysis and atomization temperatures were set at 1500 and 2400 degrees C, respectively and the use of matrix modifiers did not improve these conditions. Graphite platform presented high degradation rate, but minima changes were observed in the sensitivity or signal profile. Samples (0.3-1 mg) were weighted and introduced into the furnace using a manual solid sampling system. The linear concentration range of the calibration curve was from 100 to 1800 pg (R(2)>0.995). The characteristic mass was 7.7 pg and the limit of detection was 2.4 pg. Chromium concentration in commercial samples ranged from 0.45 to 1.06 microg g(-1) and these results were confirmed by standard addition method. The mean reproducibility was 12% (n=20 in a 3-day period) and repeatability was less than 9%. Results obtained using inductively coupled plasma optical emission spectrometry and conventional electrothermal atomic absorption spectrometry after extraction with HNO3 were around 20% lower than those obtained by the proposed procedure. It was assumed that the low results were due to incomplete extraction even using hard conditions related to temperature and pressure. The proposed procedure by DSS-ET AAS provided some advantages related to recommended pharmacopoeias methodology, as lower risks of contamination and analyte losses, higher specificity, accuracy and sensitivity, no toxic or unstable reagents are required, and calibration with aqueous standards was feasible.

Mechanism of delta-aminolevulinate dehydratase inhibition by phenyl selenoacetylene involves its conversion to diphenyl diselenide.

The mechanism of delta-aminolevulinate dehydratase (delta-ALA-D) inhibition by phenyl selenoacetylene in vitro was investigated in this study. Phenyl selenoacetylene (40-400 microM) inhibition of delta-aminolevulinate dehydratase from rat liver (low speed supernatant fraction, S1 fraction) was partially prevented by incubation under argon atmosphere and completely prevented by dithiothreitol. After incubation with S1 fraction from rat liver or cysteine (40 mM), phenyl selenoacetylene was partially converted into diphenyl diselenide, which is a stronger inhibitor of delta-aminolevulinate dehydratase than phenyl selenoacetylene. Diphenyl diselenide increased the rate of oxidation of -SH groups, while phenyl selenoacetylene did not affect such oxidation. delta-Aminolevulinate dehydratase purified from bovine liver (Sigma) was less sensitive to phenyl selenoacetylene and diphenyl diselenide than the enzyme from S1 fraction. We propose that the lower sensitivity of purified enzyme to selenides could be related to the formation of selenols due to the presence of dithiothreitol (a reducing agent) in the incubation medium. In agreement, incubation of purified enzyme (Sigma) with diphenyl diselenide (2 microM) and sodium borohydride (a reducing agent) under argon atmosphere significantly increased enzyme activity. Results obtained suggest that delta-aminolevulinate dehydratase inhibition by phenyl selenoacetylene is dependent on its conversion into diphenyl diselenide that induces oxidation of essential -SH groups of delta-aminolevulinate dehydratase. We propose that oxygen could be important in the regeneration of diphenyl diselenide leading to a catalytic oxidation of the enzyme.

Delta-aminolevulinate dehydratase inhibition by phenyl selenoacetylene: effect of reaction with hydrogen peroxide.

The effect of phenyl selenoacetylene and its selenoxide on delta-aminolevulinate dehydratase from liver of adult rats (mammalian source) and from cucumber leaves (plant source) was investigated. In vivo, selenides can be oxidized to selenoxides by flavin-containing monooxygenases and selenoxides can regenerate selenides by thiol oxidation. The compound phenyl selenoacetylene was converted to selenoxides by reaction with hydrogen peroxide. Phenyl selenoacetylene inhibited mammalian and plant delta-aminolevulinate dehydratase with an IC50 about 250 microM and >400 microM, respectively. Its selenoxide inhibited the enzyme more strongly, with IC50 values of 45 microM and 100 microM for the mammalian and plant source, respectively. The selenoxide inhibitory action was antagonized by dithiothreitol suggesting the involvement of -SH groups. Moreover, delta-aminolevulinate dehydratase from a plant source was inhibited by the selenoxide, suggesting a possible involvement of -SH groups located at a site distinct from the region implicated in Zn2+ binding in mammalian delta-aminolevulinate dehydratase. The results of the present study suggest that (i) delta-aminolevulinate dehydratase is a potential molecular target for phenyl selenoacetylene, due to the oxidation of enzyme sulfhydryl groups, and that (ii) the monooxygenation of this selenocompound, which in vivo could be possibly mediated by flavin-containing monooxigenases, increases its inhibitory effect.