Browsing by Author "Cunha, Sara C."
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- Advances in isoflavone profile characterisation using matrix solid-phase dispersion coupled to HPLC/DAD in medicago speciesPublication . Visnevschi-Necrasov, Tatiana; Barreira, João C.M.; Cunha, Sara C.; Pereira, Graça; Nunes, Eugénia; Oliveira, BeatrizAnalytical methods used in phytochemistry analysis are limited by the sample preparation step, which should ideally be fast, accurate, ecofriendly and achievable using low quantities of the sample. Matrix solid-phase dispersion (MSPD) may be a good alternative for combining extraction and purification procedures, thereby reducing the indicated limitations. Objective-Applying an MSPD extraction procedure coupled to high-performance liquid chromatography diode-array detection (HPLC/DAD) as an alternative methodology to evaluate isoflavone profiles. Methods-Isoflavone profiles were determined for the leaves of nine species of Medicago in the late flower phenological stage (one or more nodes with 50% open flowers, no seed pods). Extraction was performed following MSPD, and isoflavone profiles were characterised using HPLC/DAD. The quantified amounts were compared with previous results in different species commonly recognised as good sources of isoflavones. Results-Formononetin was the major isoflavone in most species, except M. polymorpha and M. truncatula. The isoflavone amounts were significantly different among the assayed species, with M. orbicularis and M. arabica as the major isoflavone sources, while M. rigidula presented the lowest contents. Furthermore, the detected differences allow electing the best species as a primary source of a specific isoflavone. Conclusion-The MSPD allowed good extraction efficiency, reproducibility and recovery. Some of the species showed relevant isoflavone contents, even when compared with acknowledged plant sources such as soy or red clover. To the best of our knowledge the results presented are reported for the first time in these species.
- Antioxidant activity and bioactive compounds of lettuce improved by espresso coffee residuesPublication . Cruz, Rebeca; Gomes, Teresa; Ferreira, Anabela; Mendes, Eulália; Baptista, Paula; Cunha, Sara C.; Pereira, J.A.; Ramalhosa, Elsa; Casal, SusanaThe antioxidant activity and individual bioactive compounds of lettuce, cultivated with 2.5–30% (v/v) of fresh or composted espresso spent coffee grounds, were assessed. A progressive enhancement of lettuce’s antioxidant capacity, evaluated by radical scavenging effect and reducing power, was exhibited with the increment of fresh spent coffee amounts, while this pattern was not so clear with composted treatments. Total reducing capacity also improved, particularly for low spent coffee concentrations. Additionally, very significant positive correlations were observed for all carotenoids in plants from fresh spent coffee treatments, particularly for violaxanthin, evaluated by HPLC. Furthermore, chlorophyll a was a good discriminating factor between control group and all spent coffee treated samples, while vitamin E was not significantly affected. Espresso spent coffee grounds are a recognised and valuable source of bioactive compounds, proving herein, for the first time, to potentiate the antioxidant pool and quality of the vegetables produced.
- Authentication of vegetable oils.Publication . Cunha, Sara C.; Amaral, Joana S.; Oliveira, BeatrizAuthenticity of vegetable oils continues to be a challenge and the target of many studies. Consumers expectancy on healthier products that conform to the labelled information, and the vast amount of legislation a bout the correct characterisation and classification of vegetable oils have boosted a number of scientific works on this subject. Analytical t echniques to face this challenge are, at least, as manifold as ar e the ways of adulteration, ranging from classical determination of chemical parameters to highly sophisticated instrumental and molecular biology techniques. Rather than being an exhaustive revision of published works, the aim of the present chapter is to summarise: i) the analytical methods used in the determination of the main oil components such as fatty acids, triacylglycerols, phytosterols, tocopherols and tocotrienols, phenolic compounds, pigments and volatile compounds, emphasising their importance in authenticity evaluation; ii) the alternative tech niques based on spectroscopic.
- Caracterização da fração volátil de azeitonas representativas da região de Trás-os-Montes: cvs. Cobrançosa, Madural e Verdeal TransmontanaPublication . Malheiro, Ricardo; Casal, Susana; Cunha, Sara C.; Petisca, C.; Baptista, Paula; Bento, Albino; Pereira, J.A.A fracção volátil das matérias-primas exerce um papel fundamental tanto na qualidade final dos produtos alimentares bem como no que diz respeito à sua aceitabilidade por parte do consumidor. Em Trás-os-Montes, uma região com forte tradição olivícola, a qualidade dos produtos do olival (azeite, azeitonas de mesa e pastas de azeitona) passa indiscutivelmente pela fracção volátil dos mesmos, sendo o factor varietal preponderante. Neste sentido, pretendeu-se caracterizar a fracção volátil das três cultivares de azeitona mais representativas de Trás-os-Montes (Cvs. Cobrançosa, Madural e Verdeal Transmontana) por HS-SPME e GC/MS. A azeitona foi colhida próximo do momento óptimo de colheita (índice de maturação = 3; 3ª semana de Outubro 2011), com 5 lotes por cultivar. As diferentes cultivares influenciaram tanto qualitativamente como quantitativamente a fracção volátil das azeitonas, tendo estas sido caracterizadas maioritariamente por hidrocarbonetos (tolueno), álcoois ((Z)-3-hexen- 1-ol e 1-hexanol), aldeídos (hexanal, heptanal, benzaldeído, nonanal, decanal), ésteres ((Z)-3-hexen-1-ol acetato), cetonas (6-metil-5-hepten-2-ona), monoterpenos (α-pineno, limoneno, L-mentol) e sesquiterpenos ((+)- ciclosativeno, α-copaeno, α-muuroleno). Os hidrocarbonetos, álcoois e aldeídos foram as classes químicas presentes com maior abundância, sendo o tolueno, o (Z)-3-hexen-1-ol e o nonanal os voláteis mais abundantes. O (Z)-3-hexen-1-ol juntamente com o hexanal estão associados a sensações verdes e a erva, característica sensorialmente considerada como um atributo. A fracção volátil é específica de acordo com a variedade de azeitona em estudo. Um aspecto a ter em conta a quando da elaboração de produtos à base de azeitona, tendo em vista também a aceitabilidade por parte do consumidor.
- Carotenoids of Lettuce (Lactuca sativa L.) grown on soil enriched with spent coffee groundsPublication . Cruz, Rebeca; Baptista, Paula; Cunha, Sara C.; Pereira, J.A.; Casal, SusanaThe impact of spent coffee grounds on carotenoid and chlorophyll content in lettuce (Lactuca sativa L. var. capitata) was evaluated. A greenhouse pot experiment was conducted with spent coffee amounts ranging from 0% to 20% (v/v). All evaluated pigments increased proportionally to spent coffee amounts. Lutein and β-carotene levels increased up to 90% and 72%, respectively, while chlorophylls increased up to 61%. Biomass was also improved in the presence of 2.5% to 10% spent coffee, decreasing for higher amounts. Nevertheless, all plants were characterized by lower organic nitrogen content than the control ones, inversely to the spent coffee amounts, pointing to possible induced stress. Collected data suggests that plants nutritional features, with regards to these bioactive compounds, can be improved by the presence of low amounts of spent coffee grounds (up to 10%). This observation is particularly important because soil amendment with spent coffee grounds is becoming increasingly common within domestic agriculture. Still, further studies on the detailed influence of spent coffee bioactive compounds are mandatory, particularly regarding caffeine.
- Chemometric characterization of three varietal olive oils (Cvs. cobrancosa, madural and verdeal Transmontana) extracted from olives with different maturation indicesPublication . Matos, Luís C.; Cunha, Sara C.; Amaral, Joana S.; Pereira, J.A.; Andrade, Paula B.; Seabra, Rosa M.; Oliveira, BeatrizThis paper evaluates the usefulness of three chemical parameters (compositions on tocopherols, sterols and fatty acids) as a tool to discriminate three varietal olive oils (Cvs. Cobrançosa, Madural and Verdeal Transmontana), which are permitted cultivars for the production of ‘‘Trás-os-Montes olive oil’’, a Portuguese protected designation of origin (PDO) product. The olives were collected during the year crop 2000/2001 from the same orchard, in order to eliminate the geographical and climatic influences. Lots with different maturation indices were prepared to allow the evaluation of the ripening stage on the characteristics of varietal olive oils produced from each cultivar. Statistical methods such as multivariate analysis of variance (MANOVA), principal components analysis (PCA) and cluster analysis were used to evaluate significant differences on the studied parameters. Regarding the results, the three cultivars were clearly discriminated.
- Classification PDO olive oils on the basis of their sterol composition by multivariate analysisPublication . Alves, M. Rui; Cunha, Sara C.; Amaral, J.S.; Pereira, J.A.; Oliveira, BeatrizThe sterol compositions (GLC/FID/capillary column) of monovarietal olive oils (51 samples) from the most important cultivars of northeastern Portugal (Cvs. Cobranc¸osa, Madural and Verdeal Transmontana) and 27 commercial samples of olive oils with protected denomination of origin (PDO) from the same region and cultivars were evaluated. Δ-sitosterol, Δ5-avenasterol and campesterol were the most representative sterols. Cholesterol, stigmasterol, clerosterol and Δ7-stigmastenol were also found in all samples. All studied samples respected EC Regulation N. 2568, and in all cases total sterols were remarkably higher than the minimum limit set by legislation, ranging from 2003 to 2682 mg/kg. Results were analysed with the help of several statistical techniques, including reduction of dimensionality by principal component analysis with cross-validation of the number of components, followed by the use of canonical variate predictive biplots for model development and canonical variate interpolative biplots for approximate classification of monovarietal and PDO olive oils. These biplots proved to be a very interesting solution in the present case study, overcoming the problems of interpretation and classification that arise whenever different multivariate analyses are coupled together.
- Determinação do perfil de triacilgliceróis das nozesPublication . Amaral, Joana S.; Cunha, Sara C.; Neves, Nuno; Oliveira, Beatriz; Seabra, Rosa M.Neste trabalho determinou-se o perfil em triacilgliceróis de nove cultivares de nozes (Arco, Franquette, Hartley, Lara, Marbot, Mayette, Mellanaise, Parisienne e Rego) utilizando uma técnica de HPLC/ELSD para a separação e quantificação dos compostos. A separação cromatográfica decorreu numa coluna Kromasil 100 C18 (5 μm; 250 x 4,6 mm) e uma mistura de acetona/acetonitrilo (70:30, v/v) foi utilizada como fase móvel, eluindo com um fluxo de 1ml/min num programa isocrático. O detector ELSD foi programado com os seguintes parâmetros: temperatura de evaporação 40 ºC, pressão do ar 3,5 bar e sensibilidade do fotomultiplicador 6. Foram identificados e quantificados 9 triacilgliceróis: LLnLn, LLLn, LLL, OLLn, OLL, PLL, OOL and PLO (P: ác. palmitico; O: ác. oleico; L: ác. linoleico; Ln: ác. linolénico). Na generalidade das amostras, foi detectado OOO em quantidades vestigiais, pelo que não foi quantificado. Em todas as amostras analisadas, LLL foi o TAG presente em maior percentagem, seguido pelos triacilgliceróis OLL e LLLn.
- Identification of leaf volatiles from olive (Olea europaea) and their possible role in the ovipositional preferences of olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae)Publication . Malheiro, Ricardo; Casal, Susana; Cunha, Sara C.; Baptista, Paula; Pereira, J.A.The olive fly, Bactrocera oleae (Rossi), is a monophagous pest that displays an oviposition preference among cultivars of olive (Olea europaea L.). To clarify the oviposition preference, the olive leaf volatiles of three olive cultivars (Cobrançosa, Madural and Verdeal Transmontana) were assessed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) at six different periods of olive fruit maturation and degrees of infestation. A total of 39 volatiles were identified, mainly esters and alcohols, with a minor percentage of aldehydes, ketones and terpenic compounds, including sesquiterpenes. At sampling dates with higher degrees of infestation, cv. Cobrançosa had, simultaneously, significantly lower infestation degrees and higher volatile amounts than the other two cultivars, with a probable deterrent effect for oviposition. The green leaf volatiles (GLVs) (Z)-3-hexen-1-ol and (Z)-3-hexen-1-ol acetate) were the main compounds identified in all cultivars, together with toluene. The abundance of GLVs decreas ed significantly throughout maturation, without significant differences among cultivars, while toluene showed a general increase and positive correlation with olive fly infestation levels. The results obtained could broaden our understanding of the roles of various types and amounts of olive volatiles in the environment, especially in olive fly host selection and cultivar preference.
- Influence of cultivar and environmental conditions on the triacylglycerol profile of hazelnut (Corylus avellana L.).Publication . Amaral, Joana S.; Cunha, Sara C.; Santos, Alberto; Alves, M. Rui; Seabra, Rosa M.; Oliveira, BeatrizThe oil of several hazelnut ( Corylus avellana L.) samples was extracted and evaluated for their triacylglycerol (TAG) composition. Trials were conducted in two Portuguese localities (Vila Real and Felgueiras) during three consecutive years and involved a total of 19 cultivars. The samples were analyzed by reversed-phase high-performance liquid chromatography with evaporative light-scattering detection. Sample preparation was fast and simple, consisting only of the dissolution of the oil in acetone, homogenization, and filtration, allowing this technique to be suitable for routine analyses. All samples presented a similar qualitative profile composed of eleven compounds: LLL, OLL, PLL, OOL, POL, PPL, OOO, POO, PPO, SOO and PSO (P, palmitoyl; S, stearoyl; O, oleoyl; and L, linoleoyl). The main components were OOO, LOO, and POO, reflecting the high content of oleic acid in hazelnut oils. A total of 79 different samples were studied, and the obtained data were statistically analyzed. Significant differences were verified in canonical variate plots when cultivars were grouped by country of origin. In general, the American cultivars were richer in TAGs with saturated fatty acids moieties, and the group of French, German, and English cultivars was richer in TAGs containing linoleic acid moieties. Differences were also significant when cultivars were grouped by year of production, showing that besides genetic factors, the TAG composition can be influenced by environmental factors.