In the literature there are a considerable number of chemical and biochemical tests for evaluation of in vitro antioxidant activities of pure compounds or fractions and organic extracts. These tests are important tools for screening of synthetic and natural bioactive compound as well as they can be employed in food chemistry. This work is a critical review of the main methods employed for in vitro antioxidant determination

Polygala boliviensis is found in the Brazilian semiarid region. This specie is little chemically and biologically studied. Polygala spp. have different metabolites, especially coumarins. Studies indicate that coumarins have antimalarial potential, denoting the importance of researching new active compounds from plants, since the resistance of Plasmodium strains to conventional therapy has increased. The present study aimed to evaluate the antiplasmodial activity of auraptene and poligalen against a chloroquine-resistant strain of Plasmodium falciparum. Coumarins were isolated from P. boliviensis by open column chromatography and identified by Nuclear Magnetic Resonance Spectroscopy. A cytotoxicity assay was carried out using MTT test, and the in vitro antiplasmodial activity was evaluated using the W2 strain. The antiplasmodial activity results found were IC₅₀=0.171 ± 0.016 for auraptene and 0.164 ± 0.012 for poligalen; the selectivity indexes were 78.71 and 609.76, respectively. Inverse virtual screening in the BRAMMT database by OCTOPUS 1.2 was applied to coumarins to find potential P. falciparum targets and showed higher affinity energy of auraptene for purine nucleoside phosphorylase (PfPNP) and of poligalen for dihydroorotate dehydrogenase (PfDHODH). Molecular Dynamics studies (MD and MM-GBSA) approach were applied to calculate binding energies against selected P. falciparum targets and showed that all coumarins were stable at the binding site during simulations. Furthermore, energies were favorable for complexation. This is the first report of auraptene in P. boliviensis species and of in vitro antiplasmodial activity of auraptene and poligalen. In silico studies indicated that the mechanism of action of coumarins is the inhibition of PfPNP and PfDHODH. Communicated by Ramaswamy H. Sarma

Diabetic neuropathy is a frequent complication of diabetes. Symptoms include neuropathic pain and sensory alterations—no effective treatments are currently available. This work characterized the therapeutic effect of bergenin in a mouse (C57/BL6) model of streptozotocin-induced painful diabetic neuropathy. Nociceptive thresholds were assessed by the von Frey test. Cytokines, antioxidant genes, and oxidative stress markers were measured in nervous tissues by ELISA, RT-qPCR, and biochemical analyses. Single (3.125–25 mg/kg) or multiple (25 mg/kg; twice a day for 14 days) treatments with bergenin reduced the behavioral signs of diabetic neuropathy in mice. Bergenin reduced both nitric oxide (NO) production in vitro and malondialdehyde (MDA)/nitrite amounts in vivo. These antioxidant properties can be attributed to the modulation of gene expression by the downregulation of inducible nitric oxide synthase (iNOS) and upregulation of glutathione peroxidase and Nrf2 in the nervous system. Bergenin also modulated the pro- and anti-inflammatory cytokines production in neuropathic mice. The long-lasting antinociceptive effect induced by bergenin in neuropathic mice, was associated with a shift of the cytokine balance toward anti-inflammatory predominance and upregulation of antioxidant pathways, favoring the reestablishment of redox and immune homeostasis in the nervous system. These results point to the therapeutic potential of bergenin in the treatment of painful diabetic neuropathy.

The present study primarily aims to identify the relative density and the fatty acids (methyl esters) content present in the standardized ethanol extract of leaves of M. glomerata (EPMG). Meanwhile, in a second moment, this study evaluated the effects of the EPMG on the levels of amino acids in the hippocampus, and the mechanism of sedative and anxiolytic action. Adult mice were treated with doses of 200, 300, and 400 mg/kg and evaluated in open field, elevated plus‐maze, light dark, and rotarod tests. Moreover, in the behavioral tests diazepam (GABAergic anxiolytic, 2 mg/kg) as positive control and flumazenil (GABA antagonist, 2.5 mg/kg) were used to identify mechanism of sedative and anxiolytic action produced by EPMG. The EPMG is constituted by the following compounds: methyl cinnamate, 2H‐1‐benzopyran‐2‐one, (2‐hydroxyphenyl)methyl propionate, (Z)‐methyl‐hexadec‐7‐enoate, methyl hexadecanoate, hexadecanoic acid, (Z)‐methyl‐octadec‐9‐enoate, octadecanoic acid, and squalene. This extract demonstrated anxiolytic effects, which may be mediated by GABAergic system, and was able to increase GABA levels and reduce of glutamate and aspartate concentrations in mice hippocampus, which can directly and/or indirectly assist in their anxiolytic effect. Although more studies are needed, the EPMG could represent an interesting therapeutical strategy in the treatment of anxiety.