982 resultados para neoprene phenolic adhesives


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Species with mostly asexual reproduction are interesting subjects for germination studies since variation would be more easily linked to environmental factors. Miconia ferruginata DC. is an apomictic treelet in Brazilian cerrado areas on rocky outcrops. Germination of seeds collected from individuals occurring in the Serra de Caldas Novas State Park, Goiás, was studied in three experiments under controlled conditions. Germination characteristics differed among individuals and were correlated with altitude and soil Al content. Seeds from plants growing at lower altitudes, with lower soil aluminium content, presented malformed seeds with absence of embryo which rendered lower, but better synchronized germination. The nested analysis showed that from the total variance, 78.14% for germinability, 54.56% for uncertainty of the germination process, and 68.30% for the quantity of seeds without embryo was attributed to the altitudinal effect. Individuals nested within altitude contributed up to 16.93% for the total variance. It means that there is low variability among individuals of the same altitude and high variability among individuals from different points of the slope, making clear that for the studied population the environmental effect is stronger than the genetic component to determine the seed quality. The testa of the seeds provides a mechanical dormancy which seems to be associated also with phenolic compounds, which help to disperse germination through time. Photoblastism was also registered for seeds of this species.

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The structure and histochemistry of colleters found on the vegetative and floral apices of Odontadenia lutea are described. Colleters occur on vegetative apices starting at the fourth node, with 68 to 80 colleters being found at each node. Each leaf primordium has only one colleter of axillary origin, 3-5 intra-petiolar, and 12-16 inter-petiolar (intra-stipular). There are four types of colleters: standard, bipartite standard, sessile, and bipartite sessile. Colleters on the reproductive apices alternate with the sepals and are sessile, reduced sessile, tripartite laminar sessile, or asymmetrical. All of the colleters have a central nucleus of parenchymatous cells covered by a palisade uniseriate secretory epidermis and a thin cuticle. Secretory idioblasts were observed in the parenchymatous axis. Vascularization was observed only in standard axillary and laminar colleters. Crystals were observed in the parenchyma of the axillary colleter. Histochemical tests demonstrated that there was no rupturing or distension of the cuticle during the secretion process. Mucilage was identified using the PAS reaction as well as by Mayer's reagent and Ruthenium red staining. The calycine colleters had two distinct secretory phases, the first synthesizing mucilage and the second producing phenolic compounds.

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Lignin, after cellulose, is the second most abundant biopolymer on Earth, accounting for 30% of the organic carbon in the biosphere. It is considered an important evolutionary adaptation of plants during their transition from the aquatic environment to land, since it bestowed the early tracheophytes with physical support to stand upright and enabled long-distance transport of water and solutes by waterproofing the vascular tissue. Although essential for plant growth and development, lignin is the major plant cell wall component responsible for biomass recalcitrance to industrial processing. The fact that lignin is a non-linear aromatic polymer built with chemically diverse and poorly reactive linkages and a variety of monomer units precludes the ability of any single enzyme to properly recognize and degrade it. Consequently, the use of lignocellulosic feedstock as a renewable and sustainable resource for the production of biofuels and bio-based materials will depend on the identification and characterization of the factors that determine plant biomass recalcitrance, especially the highly complex phenolic polymer lignin. Here, we summarize the current knowledge regarding lignin metabolism in plants, its effect on biomass recalcitrance and the emergent strategies to modify biomass recalcitrance through metabolic engineering of the lignin pathway. In addition, the potential use of sugarcane as a second-generation biofuel crop and the advances in lignin-related studies in sugarcane are discussed.

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Spirulina maxima, which is used as a food additive, is a microalga rich in protein and other essential nutrients. Spirulina contains phenolic acids, tocopherols and ß-carotene which are known to exhibit antioxidant properties. The aim of the present study was to evaluate the antioxidant capacity of a Spirulina extract. The antioxidant activity of a methanolic extract of Spirulina was determined in vitro and in vivo. The in vitro antioxidant capacity was tested on a brain homogenate incubated with and without the extract at 37oC. The IC50 (concentration which causes a 50% reduction of oxidation) of the extract in this system was 0.18 mg/ml. The in vivo antioxidant capacity was evaluated in plasma and liver of animals receiving a daily dose of 5 mg for 2 and 7 weeks. Plasma antioxidant capacity was measured in brain homogenate incubated for 1 h at 37oC. The production of oxidized compounds in liver after 2 h of incubation at 37oC was measured in terms of thiobarbituric acid reactant substances (TBARS) in control and experimental groups. Upon treatment, the antioxidant capacity of plasma was 71% for the experimental group and 54% for the control group. Data from liver spontaneous peroxidation studies were not significantly different between groups. The amounts of phenolic acids, a-tocopherol and ß-carotene were determined in Spirulina extracts. The results obtained indicate that Spirulina provides some antioxidant protection for both in vitro and in vivo systems.

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Achyrocline satureioides (Lam.) DC. (Compositae) is a medicinal herb used in Argentina, Uruguay, Brazil and Paraguay for its choleretic, antispasmodic and hepatoprotective properties. The presence of the flavonoid quercetin and its derivatives, and of different phenolic acids such as caffeic, chlorogenic and isochlorogenic acids in the aerial parts of this plant has led us to study the antioxidant activity of its extracts using different bioassays. The inhibition of luminol-enhanced chemiluminescence by the aqueous and methanolic extracts was used to show that their total reactive antioxidant potential index (TRAP; in µM Trolox equivalents) was 91.0 ± 15.4 and 128.1 ± 20.1 µM, respectively, while the total antioxidant reactivity index (TAR) was calculated to be 1537 ± 148 and 1910 ± 171 µM. Only the methanolic extract was capable of reducing iron (II)-dependent DNA damage. Lipid peroxidation was assessed by two different methods. The aqueous extract reduced hydroperoxide-initiated chemiluminescence in rat liver homogenates at all concentrations in a dose-dependent manner, with a calculated IC50 = 225 µg/ml, while the methanolic extract was only effective at higher concentrations (100 and 1000 µg/ml). Both aqueous and methanolic extracts were capable of reducing the production of thiobarbituric acid reactive substances (TBARS) in rat liver homogenates, with an IC50 >1000 µg/ml. The results obtained suggest that the extracts of A. satureioides possess significant free radical scavenging and antioxidant activity in vitro, a fact that should encourage future in vivo studies.

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Novel S-nitrosothiols possessing a phenolic function were investigated as nitric oxide (NO) donors. A study of NO release from these derivatives was carried out by electron spin resonance (ESR). All compounds gave rise to a characteristic three-line ESR signal in the presence of the complex [Fe(II)(MGD)2], revealing the formation of the complex [Fe(II)(MGD)2(NO)]. Furthermore, tests based on cytochrome c reduction were performed in order to study the ability of each phenolic disulfide, the final organic decomposition product of S-nitrosothiols, to trap superoxide radical anion (O2-). This study revealed a high reactivity of 1b and 3b towards O2-. For these two compounds, the respective inhibitory concentration (IC) 50 values were 92 µM and 43 µM.

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The present study was carried out to evaluate the antioxidant and antimicrobial activities of a methanol extract of Bauhinia racemosa (MEBR) (Caesalpiniaceae) stem bark in various systems. 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical, superoxide anion radical, nitric oxide radical, and hydroxyl radical scavenging assays were carried out to evaluate the antioxidant potential of the extract. The antioxidant activity of the methanol extract increased in a concentration-dependent manner. About 50, 100, 250, and 500 µg MEBR inhibited the peroxidation of a linoleic acid emulsion by 62.43, 67.21, 71.04, and 76.83%, respectively. Similarly, the effect of MEBR on reducing power increased in a concentration-dependent manner. In DPPH radical scavenging assays the IC50 value of the extract was 152.29 µg/ml. MEBR inhibited the nitric oxide radicals generated from sodium nitroprusside with an IC50 of 78.34 µg/ml, as opposed to 20.4 µg/ml for curcumin. Moreover, MEBR scavenged the superoxide generated by the PMS/NADH-NBT system. MEBR also inhibited the hydroxyl radical generated by Fenton's reaction, with an IC50 value of more than 1000 µg/ml, as compared to 5 µg/ml for catechin. The amounts of total phenolic compounds were also determined and 64.7 µg pyrocatechol phenol equivalents were detected in MEBR (1 mg). The antimicrobial activities of MEBR were determined by disc diffusion with five Gram-positive, four Gram-negative and four fungal species. MEBR showed broad-spectrum antimicrobial activity against all tested microorganisms. The results obtained in the present study indicate that MEBR can be a potential source of natural antioxidant and antimicrobial agents.

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Reciprocal selection between interacting species is a major driver of biodiversity at both the genetic and the species level. This reciprocal selection, or coevolution, has led to the diversification of two highly diverse and abundant groups of organisms, flowering plants and their insect herbivores. In heterogeneous environments, the outcome of coevolved species interactions is influenced by the surrounding community and/or the abiotic environment. The process of adaptation allows species to adapt to their local conditions and to local populations of interacting species. However, adaptation can be disrupted or slowed down by an absence of genetic variation or by increased inbreeding, together with the following inbreeding depression, both of which are common in small and isolated populations that occur in fragmented environments. I studied the interaction between a long-lived plant Vincetoxicum hirundinaria and its specialist herbivore Abrostola asclepiadis in the southwestern archipelago of Finland. I focused on mutual local adaptation of plants and herbivores, which is a demonstration of reciprocal selection between species, a prerequisite for coevolution. I then proceeded to investigate the processes that could potentially hamper local adaptation, or species interaction in general, when the population size is small. I did this by examining how inbreeding of both plants and herbivores affects traits that are important for interaction, as well as among-population variation in the effects of inbreeding. In addition to bi-parental inbreeding, in plants inbreeding can arise from self-fertilization which has important implications for mating system evolution. I found that local adaptation of the plant to its herbivores varied among populations. Local adaptation of the herbivore varied among populations and years, being weaker in populations that were most connected. Inbreeding caused inbreeding depression in both plants and herbivores. In some populations inbreeding depression in herbivore biomass was stronger in herbivores feeding on inbred plants than in those feeding on outbred ones. For plants it was the other way around: inbreeding depression in anti-herbivore resistance decreased when the herbivores were inbred. Underlying some of the among-population variation in the effects of inbreeding is variation in plant phenolic compounds. However, variation in the modification of phenolic compounds in the digestive tract of the herbivore did not explain the inbreeding depression in herbivore biomass. Finally, adult herbivores had a preference for outbred host plants for egg deposition, and herbivore inbreeding had a positive effect on egg survival when the eggs were exposed to predators and parasitoids. These results suggest that plants and herbivores indeed exert reciprocal selection, as demonstrated by the significant local adaptation of V. hirundinaria and A. asclepiadis to one another. The most significant cause of disruption of the local adaptation of herbivore populations was population connectivity, and thus probably gene flow. In plants local adaptation tended to increase with increasing genetic variation. Whether or not inbreeding depression occurred varied according to the life-history stage of the herbivore and/or the plant trait in question. In addition, the effects of inbreeding strongly depended on the population. Taken together, inbreeding modified plant-herbivore interactions at several different levels, and can thus affect the strength of reciprocal selection between species. Thus inbreeding has the potential to affect the outcome of coevolution.

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Abstract The present study describes the in vitro antimicrobial and antioxidant activity of methanol and water extracts of sweet and bitter apricot (Prunus armeniaca L.) kernels. The antioxidant properties of apricot kernels were evaluated by determining radical scavenging power, lipid peroxidation inhibition activity and total phenol content measured with a DPPH test, the thiocyanate method and the Folin method, respectively. In contrast to extracts of the bitter kernels, both the water and methanol extracts of sweet kernels have antioxidant potential. The highest percent inhibition of lipid peroxidation (69%) and total phenolic content (7.9 ± 0.2 µg/mL) were detected in the methanol extract of sweet kernels (Hasanbey) and in the water extract of the same cultivar, respectively. The antimicrobial activities of the above extracts were also tested against human pathogenic microorganisms using a disc-diffusion method, and the minimal inhibitory concentration (MIC) values of each active extract were determined. The most effective antibacterial activity was observed in the methanol and water extracts of bitter kernels and in the methanol extract of sweet kernels against the Gram-positive bacteria Staphylococcus aureus. Additionally, the methanol extracts of the bitter kernels were very potent against the Gram-negative bacteria Escherichia coli (0.312 mg/mL MIC value). Significant anti-candida activity was also observed with the methanol extract of bitter apricot kernels against Candida albicans, consisting of a 14 mm in diameter of inhibition zone and a 0.625 mg/mL MIC value.

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We determined the anti-inflammatory activity of standardized extracts of four medicinal plant species (Baccharis incarum, B. boliviensis, Chuquiraga atacamensis, Parastrephia lucida) that grow in the Argentine Puna (3800 m above sea level) and that are used to reduce oxidative stress and alleviate gout and arthritic pain. The extracts of plant aerial parts were standardized in terms of total phenolic compounds and flavone/flavanone content and free radical scavenging activity. All extracts showed high phenolic compound concentration (0.5-1.6 mg/mL), mainly flavones and flavonols (0.1-0.8 mg/mL). The extracts showed hydrogen donating ability (DPPH and ABTS) and reactive oxygen species scavenging activity (O2●-, OH-, H2O2). The ability of the extracts to inhibit cyclooxygenase enzymes (COX-1 and COX-2) was determined by calculating percent inhibition of PGE2 production measured by enzyme immunoassay. All extracts inhibited both enzymes with IC50 values of 2.0 to 16.7 µg/mL. The anti-inflammatory activity of B. incarum and C. atacamensis extracts was higher than that of B. boliviensis and P. lucida. The IC50 values obtained for indomethacin were 0.11 and 0.78 µM for COX-1 and COX-2, respectively. The present results are consistent with the anecdotal use of these species in phytotherapic preparations.

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Rosemary leaf extracts were obtained by supercritical fluid extraction (SFE) and Soxhlet extraction. Their chemical compositions were evaluated by GC-MS. The extracts were analyzed for compounds reported in the literature as showing antimicrobial and antioxidant activities. The rosemary extracts were tested with regard to antioxidant (DPPH radical scavenging and total phenolic content - Folin-Denis reagent), antibacterial (Gram-positive bacteria - Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 11778 - and Gram-negative bacteria - Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) and antifungal (Candida albicans) activities. Antioxidant, antibacterial and antifungal activities of the SFE extracts were confirmed.

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A healthy life style and a balanced diet, associated with a high fruit and vegetable intake, are linked to good health and the prevention of diseases. Apples contain bioactive compounds that help in the prevention and control of hyperlipidemia. One of the Public Health concerns in Brazil is to reduce cardiovascular diseases. Therefore, the objective of this work was to analyze the chemical composition of Gala apples and to study the effect of their consumption on weight gain, food intake, serum levels of total cholesterol, HDL-C, LDL-C, triglycerides, hepatic cholesterol and fecal cholesterol in male albino Wistar rats fed a hypercholesterolemic diet. Six animals were utilized for each treatment (control, 5, 15 and 25% apple diet), during 30 and 60 days. This study showed that one apple (200 g) can provide 14.5% of recommended total fiber and 55% of recommended vitamin C, besides supplying considerable quantities of phenolic compounds (0.38 g.100 g-1) and tannins (0.16 g.100 g-1). All animals showed a non-significant reduction in their weight gain and food intake with an increase in the concentration of apple in the diets. At the end of 30 days, all of the diets provided a significant reduction in the levels of triglycerides compared to the control group. The 15 and 25% apple diets showed significant reductions in the serum levels of total cholesterol and LDL-C and an increase in the level of fecal cholesterol in relation to the control group. The 25% apple diet provided a significant reduction in the hepatic cholesterol levels compared to the control group. After 60 days, the serum levels of total cholesterol, LDL-C, HDL-C and triglycerides in rats fed with 5, 15 and 25% apple diets were similar to the control group. This probably happened due to a revertion of the process. These results show the importance of Gala apples in the control of hyperlipidemia in rats. A diet rich in vegetables and fruits, including apples, associated to a healthy life style, over time, could prevent or reduce the risk of heart disease.

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This work evaluated the physicochemical composition of 171 red Brazilian wines from the 2006 vintage, which were represented by 21 varietals. These wines were produced by 58 Brazilian wineries in different regions of the country, with latitudes varying from 9º to 31º South. Physicochemical wine analysis was performed in the same year and discrimination in the viticultural regions, varietal wines, and wineries was performed by means of the principal component analysis (PCA). The main results show that wines from São Joaquim had higher values of A420, A520, A620, color intensity, total phenolic compounds, anthocyanins, and dry extracts, while those from Toledo had lower values of these variables; those from Vale do São Francisco had higher values of potassium, pH, density, and volatile acidity; from Serra do Nordeste A, they had higher titratable acidity; and from Planalto Superior B, higher hue. Regarding the varietal wines, PCA mainly discriminated the wines produced from the varieties Ancellotta, Teroldego, Egiodola, Refosco, Marselan, Cabernet Sauvignon, Pinotage, Pinot Noir, Malbec, Arinarnoa, Barbera, and Alfrocheiro. In relation to wineries, twenty two of them were discriminated by their higher values of some variables, i.e., three were characterized by color intensity; three by hue; eight by alcohol content; six by potassium, dry extract, density, and pH; and two by titratablel acidity.

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The artisanal production of cachaça, a beverage obtained by the fermentation of sugar cane juice after distillation, especially by small-sized producers, has traditionally used natural ferment ("fermento caipira") which consists of sugar cane juice with crushed corn, powdered rice, or citrus fruits. In despite of the difficulties in quality control due to the high level of contaminants and longer periods of preparation, the sensorial quality of the beverage may be attributed to the physiological activities of wild yeasts and even bacteria present during fermentation when this ferment is used. In this context, the aim here was to evaluate the microbiological (yeasts) and physicochemical characteristics of sugar cane juice extracted from different parts of three different varieties (RB72454, RB835486, and RB867515) of the cane stalk (lower, medium, and upper sections) in three harvesting periods (from May to December 2007) in an area under organic management. The juice from the upper section (from the eleventh internode to the top) of the sugar cane stalk could be indicated for the preparation of the natural ferment since it is as a source of yeasts and reducing sugars, especially the variety RB867515. Due to the seasonality, the best period for using this part of the sugar cane stalk is at the beginning of harvesting when the phenolic compounds are at low concentration, but there are higher number of Saccharomyces population and other yeast species. The high acidity in this section of the plant could result in a better control of bacterial contamination. These findings explain the traditional instructions of adding the upper sections for the preparation of natural ferment and can help its management in order to get a better performance with respect to organic cachaça production.

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The potential health benefits attributed to green tea and its catechins such as antioxidant effects, cancer chemoprevention, and weight loss have led to a huge increase of green tea products in the food market. The objectives of this work were to analyze and compare these products in terms of phenolic contents and in vitro antioxidant capacity including tea bags, dehydrated leaves, and ready-to-drink preparations after standardization of the infusion preparation procedure. Total phenolics content in 1 cup of the different teas varied from 90 to 341 mg of catechin equivalents, and the highest and the lowest values were both those of the ready-to-drink products. Infusions prepared from tea bags had contents varying from 96 to 201 mg.200 mL-1, and there were no significant differences among batches. The DPPH radical scavenging and the Oxygen Radical Absorbing Capacities (ORAC) varied largely among the different tea preparations, from 23 to 131 mmoles of Trolox Equivalents (TE).200 mL-1 (DPPH), and from 1.2 to 5.1 mmoles of TE.200 mL-1 (ORAC), but again there were no differences among infusions or ready-to-drink commercial preparations. However, the antioxidant capacity of ready-to-drink products was partially due to the presence of other non-phenolic compounds such as ascorbic acid