Comunidades no DSpace
Selecione uma comunidade para navegar por suas coleções
Optimization of carboxymethyl chitosan synthesis using response surface methodology and desirability function
In this paper, chitosan was reacted with monochloroacetic acid under alkaline conditions to prepare carboxymethyl chitosan. A 23 full-factorial central composite design was applied to evaluate the effect of molar ratio sodium hydroxide (NaOH)/Chitosan (Ch), time and molar ratio monochloroacetic acid (MCA)/Chitosan (Ch) on the reaction yield and on the characteristics of carboxymethyl chitosan such as average degree of substitution (DS¯ ) and solubility. An optimization strategy based on response surface methodology was used together with the desirability function approach to optimize this process. The occurrence of carboxymethylation was evidenced by FTIR and 1H NMR spectroscopy. The optimum conditions for carboxymethylation process were found to be 12.4, 10.6 h and 5 for molar ratio sodium hydroxide (NaOH)/Chitosan (Ch), time and molar ratio monochloroacetic acid (MCA)/Chitosan (Ch), respectively. Under these optimal conditions, it was possible to obtain carboxymethyl chitosan with DS of 1.86 and solubility of 99.6%.X-ray diffraction and thermogravimetry analysis showed that crystallinity and thermal stability of derivatives was lower than chitosan and decreased with increase of DS.
Potential anti-inflammatory effect of LQFM-021 in carrageenan-induced inflammation: the role of nitric oxide
The pyrazole compound LQFM-021 exhibits vasorelaxant, antinociceptive and anti-inflammatory activities. Furthermore, it has low toxicity, indicating that this compound may be considered to be a good prototype for the development of new analgesic/anti-inflammatory drugs. Therefore, the aim of this study was to investigate the potential anti-inflammatory activity of LQFM-021 using a model of carrageenan-induced inflammation as well as the mechanism of action and role of nitric oxide in this effect. Acute treatments with LQFM-021 (30 and 60 mg/kg p.o.) reduced paw edema formation dose-dependently 2 h after carrageenan injection. In the carrageenan-induced pleurisy test, LQFM-021 (30 mg/kg p.o.) reduced the leukocyte (polymorphonuclear) count in the pleural cavity, as well as decreased protein extravasation and myeloperoxidase activity. This dose of LQFM-021 increased the NO (nitrite/nitrate) and IL-4 levels and decreased the TNF-α and IL-1β levels in the pleural cavity. Moreover, pre-treatment with L-NAME reversed the effect of LQFM-021 on NO, leukocyte migration, and the TNF-α and IL-1β levels. Additionally, we observed that LQFM-021 showed weak inhibitory activity on cyclooxygenases, but reduced the PGE2 levels in the pleural cavity. Immunoblot analyses showed that LQFM-021 promoted a decrease in COX-2 levels and increase in iNOS levels. In conclusion, we demonstrated that LQFM-021 has marked anti-inflammatory activity by reducing polymorphonuclear recruitment, which is associated with the inhibition of the production of inflammatory cytokines and eicosanoids. In addition, we found that the synthase/release of nitric oxide promoted by LQFM-021 is essential for the anti-inflammatory effect observed.
Foodômica por RMN de ¹H para monitoramento da estabilidade oxidativa de margarinas submetidas ao tratamento térmico
Foods with high lipid contents are susceptible to deterioration by oxidative processes that lead to the formation of food rancid. Determining the chemical nature of lipid oxidation products presents a nutritional and health interest due to the possibility of formation of compounds related to the development of degenerative diseases such as Parkinson’s and Alzheimer’s. In this context, the present study describes the use of nuclear magnetic resonance (NMR) spectroscopy and principal component analysis (PCA) to monitor the formation of oxidation products in Brazilian table margarines subjected to the heat treatment at 80, 100, 120, 140, 160 and 180 ° C. Lipid profiles were characterized by 1H NMR experiments. Changes due to heat treatment were identified by NMR-PCA models, which indicated triacylglycerol (TAG) as the main descriptor from 160 °C. At this temperature, were identified signals evolution in 1H NMR spectra whose chemical shifts (δ) indicated the formation of aldehydes and dienes. The results were useful to highlight the need for efficient methods to maintain the oxidative stability of this type of food widely used in industrial and home cooking.
Chemical structure of a partially 3-O-methylated mannofucogalactan from edible mushroom Grifola frondosa
An unusual heteropolysaccharide was isolated from the fruiting bodies of the medicinal mushroom Grifola frondosa, via successive cold aqueous extraction, followed by fractionation through freeze-thawing, precipitation with Fehling solution and dialysis using a membrane with a size exclusion cut-off of 500 kDa. Its chemical structure was determined based on total acid hydrolysis, methylation analysis and NMR studies. The mannofucogalactan had a molar mass of 15.9 × 103 g mol−1 , which was determinate by HPSEC-MALLS. This heteropolymer showed to have a main chain of (1 → 6)-linked α-D-Galp partially substituted at O-2 by 3-O-α-D-mannopyranosyl-α-L-fucopyranosyl groups and in a minor proportion with α-L-Fucp single-unit side chains. Moreover, the presence of 3-O-Me-Galp units could also be observed in the main chain of the G. frondosa mannofucogalactan.
Sorghum starch as depressant in mineral flotation: part 1 – extraction and characterization
The mineral industry is constantly searching for new and sustainable innovations, in order to improve its results and processes. In this context, sorghum (Sorghum bicolor (L.) Moench), a widely farmed crop, was characterized and tested as an alternative depressant in mineral flotation. Starch was extracted from sorghum flour produced with grains cultivated in Brazil, resulting in an extraction yield of approximately 26%. Under polarized light microscopy, starch showed Maltese crosses, indicating that the isolation method used produced intact starch granules. SEM images indicated that the starch granules were oval or semi-spherical, with the occasional presence of broken granules and surface pores. Granule size distribution ranged from 5.5 to 30 μm with average size of 15.5 μm. With 25.5% of amylose content and relative crystallinity around 26%, the sorghum starch was classified as medium size A-type starch. FTIR spectroscopy results confirmed the presence of polysaccharide characteristic peaks, as expected. Thermal properties were measured by DCS, with results similar to cornstarch. Rheological characterization indicated a pasting temperature of 67.1 °C and viscosity peak of 2596 cP. The characterization results indicate a high potential for sorghum as depressant in mineral flotation being a feasible option for cornstarch.