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OBJECTIVES: Catechins are important components of human diet and have received special attention due to their antioxidant capacity. The purpose of this paper was to study the antioxidant action of (+)-catechin (CTQ) in the presence of vitamin B2 (riboflavin) as light-absorbing agent. Furthermore, two model compounds, catechol (CTC) and resorcinol (RSC), were selected in order to elucidate the reactive target of the CTQ molecule. The influence of pH-medium was investigated. METHODS: Stationary photolysis, polarographic detection of dissolved oxygen, reactive oxygen species (ROS)-scavengers, time-resolved near-IR phosphorescence detection, stationary, and time-resolved fluorescence and laser flash photolysis techniques were employed. RESULTS: CTQ interacts with riboflavin under visible-light photoirradiation as well as with different ROS which are generated in this mechanism. Radical-scavenging activity increases with increasing of pH-medium. DISCUSSION: pH-effect of the medium on radical-scavenging activity comes from the increased electron-donating ability of CTQ upon deprotonation. These results are very interesting due to the fact that the pH of the food products displays important variations. The [Formula: see text]-scavenging ability of CTQ, would be equal to the additive contribution of each reactive center, CTC, and RSC, present at the molecule of CTQ. However, CTQ would have a moderate ability to removal of [Formula: see text]-species at pH 7.

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Con la introducción y el desarrollo de nuevos productos que han demostrado ser eficaces en el dolor neuropático (DN), se ha generado una clara necesidad de tener un algoritmo basado en la evidencia para tratar las diferentes condiciones del DN. El objetivo de este artículo es elaborar unas recomendaciones para el tratamiento del DN que estén avaladas por la evidencia científica y que estén consensuadas por un grupo multidisciplinario de expertos en metodología y en tratamiento del dolor. La evidencia se ha obtenido de estudios de metanálisis que recogen la mayor información disponible para cada tipo de DN. La búsqueda bibliográfica se llevó a cabo por 5 revisores, que se centraron individualmente en las diferentes formas de presentación del DN. Las bases de datos consultadas fueron la Cochrane Library, EMBASE (año 2000 en adelante) y PUBMED(año 2000 en adelante), y se seleccionaron metaanálisis y ensayos clínicos aleatorizados y controlados. Finalmente, los autores, especialistas en dolor, evaluaron e hicieron las recomendaciones clínicas para el tratamiento del DN. En algunos tipos de DN, de los cuales no hay suficiente información, se han incluido recomendaciones basadas en publicaciones científicas sin evidencia, con el objetivo de que estas recomendaciones proporcionen la mayor información posible acerca de su tratamiento. Se han revisado estudios de eficacia y seguridad de neuralgia postherpética (NPH), neuropatía diabética dolorosa (NDD) y neuralgia del trigémino(NT) como paradigmas de DN periférico, y también se ha recogido la escasa información existente acerca del DN central(DNC) y el dolor simpático (DS). Con los resultados obtenidos con este estudio bibliográfico y las evidencias extraídas, se ha elaborado un algoritmo de decisión con los fármacos disponibles actualmente en la farmacopea española para la NPH y la NDD; por otro lado, y de forma independiente, para la NT y, finalmente, para el DNC y el DS.

The introduction and development of new products with demonstrated efficacy in neuropathic pain has generated a clear need for an evidence-based algorithm to treat the different types of neuropathic pain. The present article aims to provide recommendations on the treatment of neuropathic pain supported by the scientific evidence and agreed on by consensus by a multidisciplinary group of experts in methodology and pain management. The evidence was obtained from meta-analyses including the greatest amount of information available for each type of neuropathic pain. The literature search was performed by 5 reviewers, who focussed individually on the distinct forms of presentation of neuropathic pain. The databases consulted were the Cochrane Library, EMBASE (from 2000 onwards), and PUBMED (from 2000 onwards). Meta-analyses and randomized, controlled clinical trials were selected. Finally, retrieved articles were evaluated and clinical recommendations for the treatment of neuropathic pain were designed by the pain specialists. For some types of neuropathic pain, there is insufficient information. In these types of pain, recommendations based on scientific publications without evidence were included to provide the reatest possible amount of information on their treatment. Studies of safety and efficacy in postherpetic neuralgia (PHN), painful diabetic neuropathy (PDN), and trigeminal neuralgia (TN) were reviewed as paradigms of peripheral neuropathic pain. The scarce available information on central neuropathic pain (CNP) and sympathetic pain (SP) was also gathered. Based on the results obtained with this literature review and the evidence extracted, a decision algorithm was designed with the drugs currently available in the Spanish pharmacopeia for PHN and PDN, and separate decision algorithms were designed for TN and finally for CNP and S P.

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The kinetics of rose bengal-sensitized photooxidation of tyrosine and several tyrosine-derivatives (tyr-D) named tyrosine methyl ester, tyrosine ethyl ester and tyrosine benzyl ester was studied in buffered pH 11 water, and buffered pH 11 micellar aqueous solutions of 0.01 M cetyltrimethylammonium chloride (CTAC) and 0.01 M-octylphenoxypolyethoxyethanol [triton X100 (TX100)]. Through time-resolved phosphorescence detection of singlet molecular oxygen (O(2)((1)Delta(g))) and polarographic determination of oxygen consumption, the respective bimolecular rate constants for reactive (k(r)) and overall (k(t)) quenching of the oxidative species by tyr-D were evaluated. Both rate constants behave in different fashion depending on the particular reaction medium. k(r)/k(t) values, increase in the sense CTAC<

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The kinetics and mechanism of the Riboflavin (Rf)-promoted photochemical degradation with visible light of the herbicide Norflurazon (NF) has been studied by time-resolved and stationary techniques. Using light of wavelength higher than 400 nm--a region where NF is totally transparent--and with concentrations of Rf and NF of ca. 0.02 and 1 mM, respectively, only the excited triplet state of Rf ((3)Rf*) is quenched by NF, in competition with dissolved ground state triplet oxygen, O(2)((3)Sigma(g)(-)). NF degradation mainly occurs by reaction with superoxide radical anion O(2)(-) formed through two electron transfer steps: from NF to (3)Rf*, yielding Rf radical anion, and from this anion to O(2)((3)Sigma(g)(-)), regenerating ground state Rf. Although singlet molecular oxygen is also produced, NF only quenches this oxidative species in a physical mode. The global result is the photoprotection of the sensitiser and the photodegradation of NF.

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4-Hydroxyquinoline (4-OHQ) and 8-hydroxyquinoline (8-OHQ), two compounds of interest because of their bioactivity and their structural relation with bioactive products, are effectively photooxygenated when irradiated with visible light in the presence of riboflavin (Rf) (vitamin B2) in solution in air-saturated water-methanol (9:1). Rf behaves as a dye-sensitiser, since both quinolines are transparent to visible light. 8-OHQ degrades about five times faster than 4-OHQ. Kinetic data obtained through time-resolved and stationary detection of Rf-electronically excited states indicate that a superoxide radical anion-mediated mechanism exclusively operates for 4-OHQ, whereas singlet molecular oxygen--mainly--plus superoxide radical anion is the species that reacts with 8-OHQ. The sensitiser Rf, which is known to photodegrade under visible-light aerobic irradiation, is regenerated in the presence of any of the quinolines through an electron transfer process that produces superoxide radical anion. The overall picture indicates that both quinolines act as sacrificial scavengers of the photogenerated oxygen species, thus preventing the photodegradation of Rf.

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