Representação da morte e suas expectativas na visão de Petrônio: uma leitura sobre o Satyricon

Pós-graduação em História - FCHS

As religiões em Roma no Principado: Petrônio e Marcial (séculos I e II d.C)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Paulo Leminski, tradutor de latim: renovando o Satyricon, de Petrônio

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Light emission from tryptophan oxidation by hypobromous acid

The emission of ultraweak light from cells is a phenomenon associated with the oxidation of biomolecules by reactive oxygen species. The indole moiety present in tryptophan, serotonin and melatonin is frequently associated with the emission of light during the oxidation of these metabolites. This study presents results for hypobromous acid (HOBr) oxidation of tryptophan as a putative endogenous source of ultraweak light emission. We found that chemiluminescence elicited by the oxidation of tryptophan by HOBr was significantly higher than by hypochlorous acid (HOCl). This difference was related to secondary oxidation reactions, which were more intense using HOBr. The products identified during oxidation by HOCl, but depleted by using HOBr, were N-formylkynurenine, kynurenine, 1,2,3,3a,8,8a-hexahydro-3a-hydroxypyrrolo[2,3-b]-indole-2-carboxylic acid, oxindolylalanine and dioxindolylalanine. The emission of light is dependent on the free α-amino group of tryptophan, and hence, the indole of serotonin and melatonin, although efficiently oxidized, did not produce chemiluminescence. The emission of light was even greater using taurine monobromamine and dibromamine as the oxidant compared to HOBr. A mechanism based on bromine radical intermediates is suggested for the higher efficiency in light emission. Altogether, the experimental evidence described in the present study indicates that the oxidation of free tryptophan or tryptophan residues in proteins is an important source of ultraweak cellular emission of light. This light emission is increased in the presence of taurine, an amino acid present in large amounts in leukocytes, where this putative source of ultraweak light emission is even more relevant.

Antibacterial activity of alkyl gallates against Xanthomonas citri subsp. citri

The plant-pathogenic bacterium Xanthomonas citri subsp. citri is the causal agent of Asiatic citrus canker, a seriousdisease that affects all the cultivars of citrus in subtropical citrus-producing areas worldwide. There is no curative treatment for citrus canker; thus, the eradication of infected plants constitutes the only effective control of the spread ofX. citri subsp. citri. Since the eradication program in the state of São Paulo, Brazil, is under threat, there is a clear risk of X. citri subsp. citri becoming endemic in the main orange-producing area in the world. Here we evaluated the potential use of alkyl gallates to prevent X. citri subsp. citri growth. These esters displayed a potent anti-X. citri subsp. citri activity similar to that of kanamycin (positive control), as evaluated by the resazurin microtiter assay (REMA). Thetreatment of X. citri subsp. citri cells with these compounds induced altered cell morphology, and investigations of the possible intracellular targets using X. citri subsp. citri strains labeled for the septum and centromere pointed to a commontarget involved in chromosome segregation and cell division. Finally, the artificial inoculation of citrus with X. citri subsp. citri cells pretreated with alkyl gallates showed that the bacterium loses the ability to colonize its host, which indicates the potential of these esters to protect citrus plants against X. citri subsp. citri infection. © 2013, American Society for Microbiology.

Apocynin: Chemical and biophysical properties of a NADPH oxidase inhibitor

Apocynin is the most employed inhibitor of NADPH oxidase (NOX), a multienzymatic complex capable of catalyzing the one-electron reduction of molecular oxygen to the superoxide anion. Despite controversies about its selectivity, apocynin has been used as one of the most promising drugs in experimental models of inflammatory and neurodegenerative diseases. Here, we aimed to study the chemical and biophysical properties of apocynin. The oxidation potential was determined by cyclic voltammetry (Epa = 0.76V), the hydrophobicity index was calculated (logP = 0.83) and the molar absorption coefficient was determined (ε275nm = 1.1 × 104 M-1 cm-1). Apocynin was a weak free radical scavenger (as measured using the DPPH, peroxyl radical and nitric oxide assays) when compared to protocatechuic acid, used here as a reference antioxidant. On the other hand, apocynin was more effective than protocatechuic acid as scavenger of the non-radical species hypochlorous acid. Apocynin reacted promptly with the non-radical reactive species H2O2 only in the presence of peroxidase. This finding is relevant, since it represents a new pathway for depleting H2O2 in cellular experimental models, besides the direct inhibition of NADPH oxidase. This could be relevant for its application as an inhibitor of NOX4, since this isoform produces H 2O2 and not superoxide anion. The binding parameters calculated by fluorescence quenching showed that apocynin binds to human serum albumin (HSA) with a binding affinity of 2.19 × 104 M -1. The association did not alter the secondary and tertiary structure of HSA, as verified by synchronous fluorescence and circular dichroism. The displacement of fluorescent probes suggested that apocynin binds to site I and site II of HSA. Considering the current biomedical applications of this phytochemical, the dissemination of these chemical and biophysical properties can be very helpful for scientists and physicians interested in the use of apocynin.

Oxidação de lisozima por haloaminas: caracterização química e efeitos biológicos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Inhibitory effect of gallic acid and its esters on 2,2'-azobis(2-amidinopropane)hodrpchloride (AAPH)-induced hemolysis and depletion of intracellular glutathione in erythrocytes

The protective effect of gallic acid and its esters, methyl, propyl, and lauryl gallate, against 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH)-induced hemolysis and depletion of intracellular glutathione (GSH) in erythrocytes was studied. The inhibition of hemolysis was dose-dependent, and the esters were significantly more effective than gallic acid. Gallic acid and its esters were compared with regard to their reactivity to free radicals, using the DPPH and AAPH/pyranine free-cell assays, and no significant difference was obtained. Gallic acid and its esters not only failed to inhibit the depletion of intracellular GSH in erythrocytes induced by AAPH but exacerbated it. Similarly, the oxidation of GSH by AAPH or horseradish peroxidase/H(2)O(2) in cell-free systems was exacerbated by gallic acid or gallates. This property could be involved in the recent findings on pro-apoptotic and pro-oxidant activities of gallates in tumor cells. We provide evidence that lipophilicity and not only radical scavenger potency is an important factor regarding the efficiency of antihemolytic substances.

Toxicity and loss of mitochondrial membrane potential induced by Alkyl Gallates in Trypanosoma cruzi

American trypanosomiasis or Chagas disease is a debilitating disease representing an important social problem that affects, approximately, 10 million people in the world. The main aggravating factor of this situation is the lack of an effective drug to treat the different stages of this disease. In this context, the search for trypanocidal substances isolated from plants, synthetic or semi synthetic molecules, is an important strategy. Here, the trypanocidal potential of gallates was assayed in epimastigotes forms of T. cruzi and also, the interference of these substances on the mitochondrial membrane potential of the parasites was assessed, allowing the study of the mechanism of action of the gallates in the T. cruzi organisms. Regarding the preliminary structure-activity relationships, the side chain length of gallates plays crucial role for activity. Nonyl, decyl, undecyl, and dodecyl gallates showed potent antitrypanosomal effect (IC50 from 1.46 to 2.90 μM) in contrast with benznidazole (IC50 = 34.0 μM). Heptyl gallate showed a strong synergistic activity with benznidazole, reducing by 105-fold the IC50 of benznidazole. Loss of mitochondrial membrane potential induced by these esters was revealed. Tetradecyl gallate induced a loss of 53% of the mitochondrial membrane potential, at IC50 value.

Oxidation of Bovine Albumin by Hypochlorous and Hypobromous Acids: Structural and Functional Alterations

Aims: Hypochlorous (HOCl) and hypobromous (HOBr) acids are among the most powerful oxidants produced by the innate immune cells. Albumin is the predominant protein in most body fluids and is considered the most important antioxidant of blood plasma. Study Design: Oxidation of bovine albumin (BSA) and study of its structural and functional alterations. Place and Duration of Study: Faculty of Science and Faculty of Pharmaceutical Science, University of the State of Sao Paulo UNESP, between June and December 2012. Methodology: BSA was oxidized with excess of HOCl or HOBr and its structural and functional alterations were analyzed by spectroscopic techniques as UV-Vis absorption, intrinsic and synchronous fluorescence, fluorescence quenching, Rayleigh scattering and circular dichroism. Results: Both oxidants were able to deplete the intrinsic fluorescence of BSA, but HOBr was more effective than HOCl. The alterations in the synchronous fluorescence, UV-Vis absorption, and the appearance of a fluorescence band centered at 450 nm confirmed the difference between the oxidants. The oxidation did not induce aggregation of BSA as measured by Rayleigh scattering. The far-UV circular dichroism spectra showed a loss in the helical content and the near-UV-circular dichroism showed an alteration in the tertiary structure; HOBr was the more effective of the oxidants in this case. However, the oxidations did not induce significant alterations in the binding capacity of BSA, which was evaluated using hydrophobic (norfloxacin) and hydrophilic (ascorbic acid) drugs. Conclusion: These results suggest that, although highly susceptible to oxidation, the alterations did not inhibit BSA’s physiological function as a transport protein.