The effect of pH on horseradish peroxidase-catalyzed oxidation of melatonin: Production of N1-acetyl-N2-formyl-5- methoxykynuramine versus radical-mediated degradation

There is a growing body of evidence that melatonin and its oxidation product, N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), have anti-inflammatory properties. From a nutritional point of view, the discovery of melatonin in plant tissues emphasizes the importance of its relationship with plant peroxidases. Here we found that the pH of the reaction mixture has a profound influence in the reaction rate and products distribution when melatonin is oxidized by the plant enzyme horseradish peroxidase. At pH 5.5, 1 mm of melatonin was almost completely oxidized within 2 min, whereas only about 3% was consumed at pH 7.4. However, the relative yield of AFMK was higher in physiological pH. Radical-mediated oxidation products, including 2-hydroxymelatonin, a dimer of 2-hydroxymelatonin and O-demethylated dimer of melatonin account for the fast consumption of melatonin at pH 5.5. The higher production of AFMK at pH 7.4 was explained by the involvement of compound III of peroxidases as evidenced by spectral studies. On the other hand, the fast oxidative degradation at pH 5.5 was explained by the classic peroxidase cycle. © 2007 The Authors.

Avaliação antropometrica e bioquímica em pacientes renais crônicos e a ação da suplementação de ácido fólico na homocisteína, lipídeos, albumina e proteína C reativa

Pós-graduação em Alimentos e Nutrição - FCFAR

Qualidade de frutos de tomate ‘giuliana’ tratados com produtos de efeitos fisiológicos

The present work evaluated the effect of strobilurins, boscalid, plant growth regulators and vegetal extracts on the physico-chemical quality of tomato fruits (Solanum lycopersicum L.), hybrid Giuliana. The fruits from each treatment were selected and separated in 4 repetitions: control, pyraclostrobin, boscalid, pyraclostrobin + boscalid, IBA + GA(3) + kinetin, GA(4+7) + benzylaminopurine and vegetal extract. The first application was carried out at 30 days after transplant and the following at every 15 days. The evaluations were: weight loss, titratable acidity (TA), soluble solids (SS), SS/TA relation, pH, ascorbic acid content, texture, total soluble sugars (TSS), activity of pectin methyl esterase (PME) and polygalacturonase (PG). The SS content, responsible for fruit flavor, varied accordingly to the treatment, being highest for GA(4+7) + benzylaminopurine and lowest for the control. The same occurred regarding the SS/AT relation. The fruits were kept on the shelf for 9 days, at room temperature, being that at the end of this period several treatments still presented fruit in optimal consumption conditions, notably the boscalid treatment, which presented lowest weight loss, followed by pyraclostrobin. Therefore, it can be concluded that the application of the treatments did not modify the values for pH, AT and AST of the fruits. The highest PME activity was observed for the treatments with boscalid and the mixture of boscalid and pyraclostrobin, while the lowest PG activity occurred in the control and the pyraclostrobin treatment, indicating that some products accelerated the process of demethylation of pectins by PME, facilitating the action of PG.

Vanadato de bismuto sintetizado por combustão em solução na presença de diferentes combustíveis: síntese, caracterização e estudo da atividade fotocatalítica

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

Epigenetic and oncogenic regulation of SLC16A7 (MCT2) results in protein over-expression, impacting on signalling and cellular phenotypes in prostate cancer

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

Distribuição generalizada da resistência a fungicidas triazóis e evolução do gene cyp51A em populações de Pyricularia oryzae da brusone do trigo no Brasil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)