Percorrer por autor "Aires, Alfredo"
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- Antagonistic activities of Kefirgel and Kefirgel products against Staphylococcus aureus isolated from diabetic ulcersPublication . Zenão, S.; Aires, Alfredo; Dias, Carla; Saavedra, Maria José; Fernandes, ConceiçãoDiabetic foot ulcers are often complicated by infection and among pathogens the Gram-positive Staphylococcus aureus is the most common isolated. Also concomitantly, the high prevalence of methicillin-resistant S. aureus (MRSA) was significant impact on successful treatment of infected foot ulcers. In this context, the purpose of the present study was to evaluate the antibacterial properties of Kefigel®, a natural product composed by nettle (Urtica dioica L), lavender (Lavandula angustifolia Mill) and kefir grains, which have been reported as to having antibacterial activity against several diseases. Here, antibacterial effect of Kefigel® and its components were investigated against 20 S. aureus isolates (10 MSSA and 10 MRSA) collected from several diabetic foot ulcers. To assess antibacterial activity, the disk diffusion assay method, minimum inhibitory concentration (MIC), minimal bacterial activity and effects on specific growth rate, were applied. Results showed that by diffusion method, only etanolic extracts of nettle and lavender showed antibacterial activity and their effects were mainly bacteriostatic. Compared to the antibiotic gentamicin, the nettle and lavender extracts showed an efficacy between 50 and 100% relative to the antibiotic. Generally, the MRSA isolates sowed higher inhibition halos comparing MSSA isolates. In turns, Kefigel® (40mg.mL-1) affects the specific growth rate of S. aureus isolates, since after incubation for 9h almost MSSA isolates growth were inhibited. A bactericide effect was observed only against one isolates MRSA. These findings indicate a potential use of Kefigel® as a natural product having an effective effect against Staphylococus aureus. The topical use of this product for prevention of diabetic foot ulcers infections can be useful, however further investigation will be made, namely tests with high Kefigel® concentrations and synergetic effects with antibiotics.
- Antibacterial potential of Urtica dioica and Lavandula angustifolia extracts against methicillin resistant Staphylococcus aureus isolated from diabetic foot ulcersPublication . Zenão, S.; Aires, Alfredo; Dias, Carla; Saavedra, Maria José; Fernandes, ConceiçãoDespite the antibacterial potential of plant extracts against several bacterial infections, until now, no major studies have been published about the effect of lavender and nettle leaves against methicillin-sensitive and methicillin-resistant strains of Staphylococcus aureus (MSSA and MRSA, respectively). Thus, the authors studied their antibacterial potential against MSSA and MRSA from diabetic foot ulcers in order to find alternatives to the systematic use of antibiotics. Phenolic acids, flavonoids, flavones and flavonols were extracted from lavender and nettle leaves and characterized by HPLC-DAD/Vis. Disc diffusion assay and minimum inhibitory concentration (MIC) were used to assess their antibacterial activity. A direct association between the high content of hydroxycinnamic acids (chlorogenic acid, caffeic acid, rosmarinic acid) and flavonoids (quercetin) and decreasing bacterial growth activity was noted. The fact that lavender and nettle are rich in hydroxycinnamic acids and quercetin seems to explain the high antibacterial potential of these plant and the differences between them.
- Antibacterial screening of active ethanolic fractions of Urtia dioica L. against pathogenic bacteria from gastrointestinal and respiratory tractPublication . Aires, Alfredo; Dias, Carla; Zenão, S.; Rosa, Eduardo; Fernandes, Conceição; Saavedra, Maria JoséMedicinal plants are largely explored source of drug repository. Although a huge number of antibiotics are available for treatment of microbial infections, development of resistance mechanism against antibiotics is nowadays a major health concern. Therefore the needs of discover new antimicrobial compounds with high safety index is always recurrent and medicinal plants have great potential for providing novel drug leads with novel mechanism of action. Historically, this plants have always been a source of inspiration for new drug compounds. In this context we evaluate the antimicrobial potential of various extracts (produced by a partial purification in a silica gel column) of Urtica dioica L (stinging nettle) (Urticaceae) collected from Vila Real region (Portugal), against 10 different bacteria isolates collected from clinical patients (gastrointestinal segments and respiratory tract), namely 4 Gram positive [2 Staphylococcus aureus (MRSA), Staphylococus aureus (MSSA), Staphylococcus saprophyticus, and Enterococcus faecalis]and 5 Gram negative[Salmonella thyphi, Echerichia coli, Klebsiela pneumoniae, Pseudomonas aeruginosa and Proteus mirabilis]. The current study represents the investigation of antimicrobial activity of U. dioica from four fractions (Hexane, Ethyl-acetate, ethanol and water) that were prepared using sequential fractionating method by column chromatography. The antibacterial activity was assessed by disk diffusion and minimum inhibitory concentration methods. The phytochemical composition of U. dioica fractions were assessed by HPLC-UV-DAD. Our results showed that only ethanolic fractions had antibacterial activity but only in S. aureus (MRSA and MSSA), S. saprophyticus and E. faecallis isolates. Thus, only the Gram positives were affected by U.doica extracts. The inhibition zone diameter halos ranges from 0 to 23 mm and the minimum inhibitory concentration (MIC) were6.25 mg.mL-1 for MRSA isolates and 0.78 mg.mL-1 for S. saprophyticus and E. faecalis. Our results show a direct association between the antibacterial activities and high content of phytochemicals detected in the ethanolic fractions particularly with phenolic acids (chlorogenic and ferulic acids) and flavonols (rutin, isoquercetin and quercetin isomers). Our observations suggest the importance of ethnomedicinal use of U. dioica, which could be used by the pharmaceutical industry as source of a natural antimicrobial agents and antioxidant compounds.
- Antimicrobial activity against Staphylococcus aureus (MRSA and MSSA): bioactive compounds potencialPublication . Ballem, Andressa; Fernandes, Conceição; Zenão, S.; Gaspar, João; Carvalho, E.; Carvalho, J.A.; Aires, Alfredo; Rosa, Eduardo; Saavedra, Maria JoséHospital infections in diabetic patients are associated with Staphylococcus aureus, including S. aureus resistant to methicillin (MRSA). Besides their increase incidence, MRSA is considered one of the main pathogens causing nosocomial infections and, furthermore, many of these MRSA isolates are becoming multidrug resistant, constituting a public health problem. As a consequence, there is an increase for the search of alternatives to antibiotics, either by synthesis of new compounds or by the research for natural products with antibacterial properties. In this context, this work investigated the antibacterial effect of natural compounds present in plants (Urtica dioica L. and Lavandula angustifolia Mill) in several Gram-positive isolates, collected from diabetic foot ulcers, namely Staphylococcus aureus (MRSA and MSSA). Different plant extracts (extraction in ethanol, acetone and water) were tested and the antibacterial activity was evaluated by disk diffusion assay method, minimum inhibitory concentration (MICs), minimum bactericide concentration (MBC) and growth rate (µ). Spectrophotometry methods were used to assess the total phenolic content and HPLC-DAD/VIS method was used to identify and quantify the phytochemicals present in the plant extracts. Best antibacterial activity against both MRSA and MSSA was observed with the ethanolic extracts, reaching an effectiveness of 100%, in relation to the antibiotic gentamicin. For both plant extracts, the effect on bacterial growth rate was predominantly bacteriostatic. These findings indicate a potential of these plant extracts as a natural product with antimicrobial activity. Their use in formulations, alone or with synergistic effect with conventional antibiotics could be an alternative to limit the infections of these bacteria.
- Assessment of the effect of different deficit irrigation strategies on polyphenolic compounds of olives (cv. “Cobrançosa”)Publication . Silva, Marília; Aires, Alfredo; Almeida, Arlindo; Fernandes-Silva, AnabelaOlive tree (Olea europaea L.) is one of the most important fruit trees of Mediterranean countries due its food products, table olives and olive oil that are well known by its high biophenol contents. Different water regimes affect the general development and the composition of olive fruit [1] leading to slight changes in the taste of the resulting oil [2] Particular attention has been given to the changes in phenolic compounds. Although this is not a general effect and responses may differ in relation to the genotype, generally olives harvested from irrigated trees show a lower accumulation of total phenols [3]. Contrasting evidence has not completely clarified the relation between water availability and the oleuropein content in the drupes [4]. This study was undertaken to assess the effect of different deficit irrigation strategies on polyphenolic compounds of olives. Field trials took place in a typical olive growing area of Northeast Portugal region, Vilariça Valley (“Terra Quente Transmontana”), in 2013 year in an irrigated olive orchard with “Cobrançosa Transmontana” cultivar. Four irrigation regimes were applied: i) a well irrigated treatment (T1), that received a seasonal equivalent water amount to satisfied crop evapotranspiration (100%ETc), irrigated on the two sides; three deficit irrigation treatment: two sustained deficit irrigation treatment: ii) irrigated with 40% T1 on two side (SDI40) and iii) irrigated with 75% T1 on two side 75% (SDI75) and a four treatment iv) Partial Root Drying System (PRD100), irrigated with 100% of T1 on one side, switching every 15 days. Total content of polyphenols (TP) and ortho-diphenols decreased during maturation and were affected by irrigation treatment (p<0.05). At the first picking date, with maturation index (IM) = 0, no significant differences were observed in TP between deficit irrigation treatments, with 19,072; 19,275 and 19,439 mg GAE kg-1 dw for SDI40; SDI75 and PRD100, respectively. The differences were only observed between these and T1treatment (100%ETc) that showed the lower values (15,270 mg GAE kg-1 dw). Curiously, at the harvest (IM = 3.2-3.5) the highest values of TP were observed in SDI40 treatment with significant differences. TP in the others treatments decreased and weren’t no different. Concerning to individual phenolic compounds, oleuropein and verbascoside are the most representative in all treatments. Olives with higher values (149.96 ½g. g-1 dw) of oleuropein were submitted to the higher level of water deficit (SDI40), followed by treatments SDI75 (143.55 ½g.g-1 dw), PRD100 (125.78 ½g.g-1 dw) and finally by 100% ETc (122.53 ½g.g-1 dw). Verbascoside was the main hydroxycinnamic acid present in olives, with the higher values observed in treatments with low irrigation (SDI40 and PRD100). The content of the individual phenolic compounds including phenolic alcohols, and secoiridoids were affected by irrigation, being lower with the increase of the amount of water applied.
- Combined soil and foliar nitrogen fertilization effects on rainfed almond tree performancePublication . Morais, Maria Cristina; Aires, Alfredo; Barreales, David; Rodrigues, M.A.; Ribeiro, A.C.; Gonçalves, Berta C.C.; Silva, A.P.Cultivation of almond in the Mediterranean region is traditionally done under rainfed conditions and poorly established cropping practices resulting in low yields. Despite the importance of nitrogen (N) fertilization to increase yield in cultivated species, this practice is usually neglected in rainfed managed almond orchards. Selection of the most appropriate rate and method of nitrogen (N) application are utmost factors to maximize almond yield in the considered conditions. Therefore, the aim of this study was to understand how soil and foliar N fertilization affect physiological and biochemical performance, almond yield, and fruit quality of almond trees grown under rainfed conditions. A 3-year experiment comprised four soil-applied N rates (0, 25, 50, and 100 kg ha−1) with and without 0.5% foliar N application of urea during the growing season, which was arranged in a randomized complete block design with three replications. Nitrogen soil fertilization did not influence the leaf gas exchange parameters and the content of photosynthetic pigments but significantly improved almond yield. There were no particular advantages in foliar fertilization. Soil application of small doses of fertilizer (e.g., 25 kg N ha−1) per year was optimal for maintaining appropriate physiological behavior of almond trees under the conditions in which the experiment was carried out, without compromise almond yield and fruit quality. Thus, the annual application at 25 kg N ha−1 enables substantial reduction of almond production costs being a positive contribution to environment-friendly farming practices.
- Crescimento de Chlorella Vulgaris (chlorophyta unicelular) na presença de compostos fenólicosPublication . Silva, Andreina Sofia Nunes da; Geraldes, Ana Maria; Aires, Alfredo; Fernandes, ConceiçãoNeste trabalho avaliou-se o efeito de diferentes tipos de extractos da planta de rosmaninho (Rosmarinus officinalis) ricos em compostos fenólicos, no crescimento e na fisiologia da microalga Chlorella vulgaris. Os extractos foram obtidos por infusão aquosa a quente e a frio, esta ultima com dois períodos de extração (5 e 21 dias). Os ensaios foram desenvolvidos em culturas batch com extratos à concentração de 10%, 25% e 30% (v/v). Os resultados mostraram para os extractos a frio que o crescimento da microalga foi afetado apenas com extratos de 21 dias, levando ao aumento da taxa específica de crescimento (μ) e da densidade celular, bem como da concentração de clorofila a (Chl a) e do teor em proteinas, numa relação direta com a concentração de extrato testada. A exposição aos extractos a quente apesar de levar ao aumento de µ e da densidade celular final de C. vulgaris, concomitantemente induziu alguma toxicidade a nível fisiológico, visível pela diminuição dos teores de Chl a e proteínas. Os compostos fenólicos identificados por HPLC, nestes dois tipos de extratos, mostraram diferenças qualitativas e quantitativas. O extrato a frio apresentou essencialmente ácido rosmarínico e quercetina, enquanto que no extrato a quente foram quantificados sete compostos distintos, sendo os mais abundantes os ácidos rosmarínico e gálico. Considerando o perfil de compostos fenólicos encontrado, é possível concluir que o grau de inibição/estimulo do crescimento de C. vulgaris está relacionado com a concentração e composição em compostos fenólicos dos extractos estudados.
- Effects of foliar and soil boron fertilization on yield, leaf physiological traits and fruit attributes in rainfed almond orchardsPublication . Silva, A.P.; Aires, Alfredo; Barreales, David; Rodrigues, M.A.; Ribeiro, A.C.; Gonçalves, Berta M.; Morais, Maria C.Boron (B) fertilizers are recognized as essential for ensuring yield and fruit quality. However, the importance of soil and foliar B fertilization in almond orchards under rainfed conditions is presently unclear. To address this literature gap, in the present study, the impact of soil and foliar application of B on leaf gas exchange, leaf photosynthetic pigments, yield, and fruit quality in almonds was investigated across three consecutive growing seasons. Boron fertilizer was applied to the soil at four rates (0, 1, 2, and 3 kg ha−1) in the presence or absence of foliar application (0.36 g L−1) of the same micronutrient. Borax pentahydrate was used as the B source. When compared to foliar B fertilization, the soil application of B positively affected the gas exchange parameters, mainly the net CO2 assimilation rate, stomatal conductance, and transpiration rate (percentage of gain between 15% and 80%), but did not influence the chlorophyll content. The almond yield and fruit characteristics were also enhanced (about 25–72%) in response to lower soil B fertilization rates. In the 3 kg ha−1 dose, B had an adverse effect on the yield and resulted in lighter fruits. On the other hand, foliar B fertilization did not benefit any of the evaluated parameters. Overall, these results suggest that, under the studied conditions, almond orchards do not respond to higher B rates in soil or foliar B fertilization.
- Effects of soil and foliar application of nitrogen and boro non a.tocoferol and antioxidant properties of two varieties (Glorieta and Masbovera) of almond grown in Northeast of PortugalPublication . Aires, Alfredo; Morais, Cristina; Prgomet, Iva; Oliveira, Ivo; Bernardo, Sara; Afonso, Sílvia Martins; Carvalho, Rosa Paula; Barreales, David; Rodrigues, M.A.; Ribeiro, A.C.; Gonçalves, Berta C.C.; Silva, A.P.The aim of the current study was to determine the effects of two fertilizers, boron and nitrogen, on the nutritional quality of two cultivars od almonds (Prunus Dulcis Mill.) Glorieta and Masbovera grown in Alfandega da Fé region, Northeast of Portugal.
- Phenolics and antioxidant activity of green and red sweet peppers from organic and conventional agriculture: A comparative studyPublication . Guilherme, Rosa; Aires, Alfredo; Rodrigues, Nuno; Peres, António M.; Pereira, J.A.Today, consumers are very concerned regarding food quality, nutritional composition and positive health effects of consumed foods. In this context, the preference and consumption of organic products has been increasing worldwide. In the present work, sweet peppers in two maturation stages (i.e., green and red peppers) from organic and conventional production systems were evaluated in regards to phenolic composition and antioxidant activity. Nine phenolic compounds were identified and quantified by a high-performance liquid chromatography-diode-array detector (HPLC-DAD), namely resveratrol, meta-coumaric acid, ortho-coumaric acid, clorogenic acid, caffeic acid, myricetin, rutin, luteolin-7-O-glucoside and quercitin-3-O-rhamnoside. In contrast to the production system, the maturation stage showed a pronounced significant effect on the phenolic composition of the studied sweet peppers; in general, green peppers possessed higher contents than red ones. Meta-coumaric acid, ortho-coumaric acid and quercitin-3-O-rhamnoside were more abundant in green conventional peppers and chlorogenic acid, caffeic acid and rutin were found in higher levels in red organic peppers. Regarding the antioxidant activity, green conventional peppers showed the highest DPPH, ABTS•+ and total reducing capacities, while red conventional peppers had higher TEAC values. Finally, principal component analysis showed that the phenolic composition together with the antioxidant capacities could be used to differentiate the production system and the maturation stage of sweet peppers. This finding confirmed that both factors influenced the peppers’ phenolic composition and antioxidant capacity, allowing their possible use as maturation–production biomarkers.