Chromatographic techniques for the determination of free phenol in foundry resins

Phenol is a toxic compound present in a wide variety of foundry resins. Its quantification is important for the characterization of the resins as well as for the evaluation of free contaminants present in foundry wastes. Two chromatographic methods, liquid chromatography with ultraviolet detection (LC-UV) and gas chromatography with flame ionization detection (GC-FID), for the analysis of free phenol in several foundry resins, after a simple extraction procedure (30 min), were developed. Both chromatographic methods were suitable for the determination of phenol in the studied furanic and phenolic resins, showing good selectivity, accuracy (recovery 99–100%; relative deviations <5%), and precision (coefficients of variation <6%). The used ASTM reference method was only found to be useful in the analysis of phenolic resins, while the LC and GC methods were applicable for all the studied resins. The developed methods reduce the time of analysis from 3.5 hours to about 30 min and can readily be used in routine quality control laboratories.

Electroanalytical study of the pesticide ethiofencarb

A detailed study of voltammetric behavior of ethiofencarb (ETF) is reported using glassy carbon electrode (GCE) and hanging mercury drop electrode (HMDE). With GCE, it is possible to verify that the oxidative mechanism is irreversible, independent of pH, and the maximum intensity current was observed at +1.20 V vs. AgCl/Ag at pH 1.9. A linear calibration line was obtained from 1.0x10-4 to 8.0x10-4 mol L-1 with SWV method. To complete the electrochemical knowledge of ETF pesticide, the reduction was also explored with HMDE. A well-defined peak was observed at –1.00V vs. AgCl/Ag in a large range of pH with higher signal at pH 7.0. Linearity was obtained in 4.2x10-6 and 9.4x10-6 mol L-1 ETF concentration range. An immediate alkaline hydrolysis of ETF was executed, producing a phenolic compound (2-ethylthiomethylphenol) (EMP), and the electrochemical activity of the product was examined. It was deduced that it is oxidized on GCE at +0.75V vs. AgCl/Ag with a maximum peak intensity current at pH 3.2, but the compound had no reduction activity on HMDE. Using the decrease of potential peak, a flow injection analysis (FIA) system was developed connected to an amperometric detector, enabling the determination of EMP over concentration range of 1.0x10-7 and 1.0x10-5 mol L-1 at a sampling rate of 60 h-1. The results provided by FIA methodology were performed by comparison with results from high-performance liquid chromatography (HPLC) technique and demonstrated good agreement with relative deviations lower than 4%. Recovery trials were performed and the obtained values were between 98 and 104%.

Antioxidant properties of hydroxycinnamic acids: a review of structure- activity relationships

Hydroxycinnamic acids (HCAs) are important phytochemicals possessing significant biological properties. Several investigators have studied in vitro antioxidant activity of HCAs in detail. In this review, we have gathered the studies focused on the structure-activity relationships (SARs) of these compounds that have used medicinal chemistry to generate more potent antioxidant molecules. Most of the reports indicated that the presence of an unsaturated bond on the side chain of HCAs is vital to their activity. The structural features that were reported to be of importance to the antioxidant activity were categorized as follows: modifications of the aromatic ring, which include alterations in the number and position of hydroxy groups and insertion of electron donating or withdrawing moieties as well as modifications of the carboxylic function that include esterification and amidation process. Furthermore, reports that have addressed the influence of physicochemical properties including redox potential, lipid solubility and dissociation constant on the antioxidant activity were also summarized. Finally, the pro-oxidant effect of HCAs in some test systems was addressed. Most of the investigations concluded that the presence of ortho-dihydroxy phenyl group (catechol moiety) is of significant importance to the antioxidant activity, while, the presence of three hydroxy groups does not necessarily improve the activity. Optimization of the structure of molecular leads is an important task of modern medicinal chemistry and its accomplishment relies on the careful assessment of SARs. SAR studies on HCAs can identify the most successful antioxidants that could be useful for management of oxidative stress-related diseases.

Wine and grape polyphenols — a chemical perspective

Phenolic compounds constitute a diverse group of secondary metabolites which are present in both grapes and wine. The phenolic content and composition of grape processed products (wine) are greatly influenced by the technological practice to which grapes are exposed. During the handling and maturation of the grapes several chemical changes may occur with the appearance of new compounds and/or disappearance of others, and consequent modification of the characteristic ratios of the total phenolic content as well as of their qualitative and quantitative profile. The non-volatile phenolic qualitative composition of grapes and wines, the biosynthetic relationships between these compounds, and the most relevant chemical changes occurring during processing and storage will be highlighted in this review.

Extração e caracterização de extratos de Jatropha gossypiifolia L.: avaliação da sua atividade antimicrobiana e antioxidante

Trabalho Final de Mestrado para obtenção do grau de mestre em Engenharia Química e Biológica

Effect of peel and seed removal on the nutritional value and antioxidant activity of tomato (Lycopersicon esculentum L.) fruits

The effect of peel and seed removal, two commonly practiced procedures either at home or by the processing industry, on the physicochemical properties, bioactive compounds contents and antioxidant capacity of tomato fruits of four typical Portuguese cultivars (cereja, chucha, rama and redondo) were appraised. Both procedures caused significant nutritional and antioxidant activity losses in fruits of every cultivar. In general, peeling was more detrimental, since it caused a higher decrease in lycopene, bcarotene, ascorbic acid and phenolics contents (averages of 71%, 50%, 14%, and 32%, respectively) and significantly lowered the antioxidant capacity of the fruits (8% and 10%, using DPPH. and b-carotene linoleate model assays, correspondingly). Although seeds removal favored the increase of both color and sweetness, some bioactive compounds (11% of carotenoids and 24% of phenolics) as well as antioxidant capacity (5%) were loss. The studied cultivars were differently influenced by these procedures. The fruits most affected by peeling were those from redondo cultivar (-66% lycopene, -44% b-carotene, -26% ascorbic acid and -38% phenolics). Seeds removal, in turn, was more injurious for cereja tomatoes (-10% lycopene, -38% b-carotene, -25% ascorbic acid and -63% phenolics). Comparatively with the remaining ones, the rama fruits were less affected by the trimming procedures.

Organic versus conventional tomatoes: Influence on physicochemical parameters, bioactive compounds and sensorial attributes

The effect of organic and conventional agricultural systems on the physicochemical parameters, bioactive compounds content, and sensorial attributes of tomatoes (‘‘Redondo’’ cultivar) was studied. The influence on phytochemicals distribution among peel, pulp and seeds was also accessed. Organic tomatoes were richer in lycopene (+20%), vitamin C (+30%), total phenolics (+24%) and flavonoids (+21%) and had higher (+6%) in vitro antioxidant activity. In the conventional fruits, lycopene was mainly concentrated in the pulp, whereas in the organic ones, the peel and seeds contained high levels of bioactive compounds. Only the phenolic compounds had a similar distribution among the different fractions of both types of tomatoes. Furthermore, a sensorial analysis indicated that organic farming improved the gustative properties of this tomato cultivar.

Geossintéticos em vias de comunicação: influência das condições climáticas

Trabalho de Dissertação de Natureza Científica para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Vias de Comunicação e Transportes

Biochemistry of grape berries: post-genomics approaches to uncover the effects of water deficits on ripening

Dissertation presented to obtain the Ph.D degree in Biochemistry, Plant Physiology

Brazilian fruit pulps as functional foods and additives: Evaluation of bioactive compounds

Eight tropical fruit pulps from Brazil were simultaneously characterised in terms of their antioxidant and antimicrobial properties. Antioxidant activity was screened by DPPH radical scavenging activity (126–3987 mg TE/100 g DW) and ferric reduction activity power (368–20819 mg AAE/100 g DW), and complemented with total phenolic content (329–12466 mg GAE/100 g DW) and total flavonoid content measurements (46–672 mg EE /100 g DW), whereas antimicrobial activity was tested against the most frequently found food pathogens. Acerola and açaí presented the highest values for the antioxidant-related measurements. Direct correlations between these measurements could be observed for some of the fruits. Tamarind exhibited the broadest antimicrobial potential, having revealed growth inhibition of Pseudomonas aeruginosa. Escherichia coli, Listeria monocytogenes, Salmonella sp. and Staphylococcus aureus. Açaí and tamarind extracts presented an inverse relationship between antibacterial and antioxidant activities, and therefore, the antibacterial activity cannot be attributed (only) to phenolic compounds.

Impact of boiling on phytochemicals and antioxidant activity of green vegetables consumed in the Mediterranean diet

The effect of boiling (10 minutes) on eleven green vegetables frequently consumed in the Mediterranean diet was evaluated. For that, some physicochemical parameters and the contents of vitamin C, phenolics and carotenoids, as well as the antioxidant activity, were determined in raw and boiled samples. The raw vegetables analysed in this study were good sources of vitamin C, carotenoids and phenolic compounds, with contents ranging from 10.6 to 255.1 mg/100 g, 0.03 to 3.29 mg/100 g and 202.9 to 1010.7 mg/100 g, respectively. Boiling promoted losses in different extensions considering both the different bioactive compounds and the distinct vegetables analysed. Contrary to phenolics (more resistant), vitamin C was the most affected compound. Boiling also originated significant losses in the antioxidant activity of the vegetables. Considering all the parameters analysed, the vegetables most affected by boiling were broccoli and lettuce. The least affected ones were collard and tronchuda cabbage.

Monomeric and oligomeric flavan-3-ols and antioxidant activity of leaves from different Laurus sp.

The phenolic profile and antioxidant activity of three endemic Laurus sp. from Portugal were analysed. Dried leaves of L. nobilis L., L. azorica (Seub.) Franco, and L. novocanariensis Rivas Mart., Lousã, Fern. Prieto, E. Días, J. C. Costa & C. Aguiar, collected in the mainland and in the Azores and Madeira archipelagos, respectively, were used to prepare different extracts (aqueous, ethanolic and hydroalcoholic). They were studied regarding their DPPH˙ scavenging activity, total phenolic and flavonoid contents, and the main phenolic compounds were identified by HPLC-DAD-ESI-MS/MS. Total flavonoid contents were 30.1, 46.3, and 36.7 mg of epicatechin equivalents per g of sample (dry weight) for L. nobilis, L. azorica and L. novocanariensis, respectively. Epicatechin was the major compound, representing ∼12.1% of total flavan-3-ols in L. nobilis, ∼25.6% in L. azorica, and ∼19.9% in L. novocanariensis. Although all samples presented a similar phenolic profile, significant differences were observed in their total contents and antioxidant activity.

Cultivo e avaliação do potencial da microalga Chlorella zofingiensis para a produção de biodiesel e produtos de valor acrescentado

O presente trabalho tem como objetivo o cultivo da microalga Chlorella zofingiensis, e a avaliação da sua potencial aplicação na produção de biodiesel e de produtos de valor acrescentado, de entre os quais se destacam os antioxidantes. Com o intuito da produção de biocombustível é necessário efetuar o cultivo da microalga num volume que permita a obtenção de elevada quantidade de biomassa para a concretização do trabalho. Além deste biocombustível, existe ainda a possibilidade de valorização de alguns produtos com valor comercial, como é o caso da astaxantina, a saber na área farmacêutica, alimentar ou até mesmo cosmética. O cultivo da microalga foi feito em meio Bold’s Basal Medium (BBM), inicialmente em matrazes de 5 L e, quando se obteve uma cultura suficientemente densa, inocularam-se fotobiorreatores de 50 L. Conseguiu-se atingir uma concentração máxima de 0,76 g/L, no reator de 5 L, após cerca de 6 semanas de ensaio. Por sua vez, em fotobiorreatores de 50 L, a concentração máxima obtida foi de 0,4 g/L, após 4 semanas de ensaio. Nestas culturas foi possível obter-se uma percentagem lipídica de 7 %, apresentado concentração de pigmentos por litro de cultura na ordem dos 10 mg/L, 4 mg/L e 2 mg/L de clorofila a, clorofila b e carotenoides totais, respetivamente. Com esta percentagem lipídica recuperaram-se 400 mg de óleo, obtendo-se posteriormente 280 mg de biodiesel. Pela análise à amostra de biodiesel obtida foi possível obter o perfil lipídico desta microalga, quando cultivada em meio BBM, sendo 41% de ácido palmítico (C16:0), 9% de ácido esteárico (C18:0), 27% de ácido oleico (C18:1) e 23% de ácido linoleico (C18:2). Os resultados obtidos mostram que a Chlorella zofingiensis é uma microalga com interesse potencial para a produção de clorofila e carotenóides, mas não para o óleo para a produção de biodiesel.

Neuroprotection for optic nerve disorders.

The concept that optic nerve fiber loss might be reduced by neuroprotection arose in the mid 1990s. The subsequent research effort, focused mainly on rodent models, has not yet transformed into a successful clinical trial, but provides mechanistic understanding of retinal ganglion cell death and points to potential therapeutic strategies. This review highlights advances made over the last year. In excitotoxicity and axotomy models retinal ganglion cell death has been shown to result from a complex interaction between retinal neurons and Müller glia, which release toxic molecules including tumor necrosis factor alpha. This counteracts neuroprotection by neurotrophins such as nerve growth factor, which bind to p75NTR receptors on Müller glia stimulating the toxic release. Another negative effect against neurotrophin-mediated protection involves the action of LINGO-1 at trkB brain-derived neurotrophic factor (BDNF) receptors, and BDNF neuroprotection is enhanced by an antagonist to LINGO-1. As an alternative to pharmacotherapy, retinal defences can be stimulated by exposure to infrared radiation. The mechanisms involved in glaucoma and other optic nerve disorders are being clarified in rodent models, focusing on retrograde degeneration following axonal damage, excitotoxicity and inflammatory/autoimmune mechanisms. Neuroprotective strategies are being refined in the light of the mechanistic understanding.

Skin fibroblast model to study an impaired glutathione synthesis: consequences of a genetic polymorphism on the proteome.

An impaired glutathione (GSH) synthesis was observed in several multifactorial diseases, including schizophrenia and myocardial infarction. Genetic studies revealed an association between schizophrenia and a GAG trinucleotide repeat (TNR) polymorphism in the catalytic subunit (GCLC) of the glutamate cysteine ligase (GCL). Disease-associated genotypes of this polymorphism correlated with a decrease in GCLC protein expression, GCL activity and GSH content. To clarify consequences of a decreased GCL activity at the proteome level, three schizophrenia patients and three controls have been selected based on the GCLC GAG TNR polymorphism. Fibroblast cultures were obtained by skin biopsy and were challenged with tert-butylhydroquinone (t-BHQ), a substance known to induce oxidative stress. Proteome changes were analyzed by two dimensional gel electrophoresis (2-DE) and results revealed 10 spots that were upregulated in patients following t-BHQ treatment, but not in controls. Nine corresponding proteins could be identified by MALDI mass spectrometry and these proteins are involved in various cellular functions, including energy metabolism, oxidative stress response, and cytoskeletal reorganization. In conclusion, skin fibroblasts of subjects with an impaired GSH synthesis showed an altered proteome reaction in response to oxidative stress. Furthermore, the study corroborates the use of fibroblasts as an additional mean to study vulnerability factors of psychiatric diseases.