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Determinação de compostos bioativos em frutas e vegetais consumidos na Região Autónoma da Madeira
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Abstract(s)
Os compostos bioativos são metabolitos secundários que ocorrem em pequenas quantidades nas plantas. Para além de atuarem como sistema de defesa, estes compostos também contribuem para o bem-estar humano, devido à sua eficiente ação antioxidante, anticancerígena, antimicrobiana, entre outros. Neste trabalho, foram analisadas a composição bioativa e a atividade antioxidante de 11 amostras vegetais, tipicamente, consumidas na RAM, nomeadamente a beterraba, cebola roxa e amarela, cenoura laranja e branca, agrião, brócolos, espinafres, alho, tomate e tomate inglês. Através dos extratos metanólicos obtidos destas matrizes, quantificou-se o teor total dos compostos fenólicos, de flavonoides, de antocianinas, de betalaínas e de carotenoides. A capacidade antioxidante foi, igualmente testada através dos métodos DPPH, ABTS e FRAP, tendose verificado maior atividade nas amostras de cebola roxa, tomate inglês e beterraba. Utilizando a metodologia de extração QuEChERS seguida de análise por cromatografia líquida de ultra-eficiência (UHPLC), foi possível identificar e quantificar alguns polifenóis da polpa destas matrizes, onde a catequina e os ácidos gentísico e ferúlico foram os polifenóis mais abundantes. Adicionalmente, efetuou-se o estudo da composição volátil destas amostras, com recurso à microextração em fase sólida (HS-SPME) seguida de análise por cromatografia em fase gasosa acoplada à espetrometria de massa (GC-MS). Foram identificados 320 compostos voláteis pertencentes a diferentes famílias químicas. Com base nos resultados obtidos, verificou-se que os compostos terpénicos são predominantes na beterraba (61%), na cenoura laranja (58%) e na cenoura branca (61%), enquanto que os compostos organossulfurados foram encontrados quase exclusivamente nas amostras de cebola, alho e agrião. Os álcoois e aldeídos são os grupos de compostos voláteis predominantes nos brócolos e nos espinafres, enquanto que os frutos da família Solanaceae, são caraterizados por ésteres, no caso do tomate inglês, e aldeídos no caso do tomate.
Bioactive compounds are secondary metabolites that occur in small amounts in plants. In addition to acting as a defense system, these compounds also contribute to human well-being, due to its efficient antioxidant, anticancer, antimicrobial action, among others. In this work, the bioactive composition and antioxidant capacity of 11 vegetables samples typically consumed in RAM, namely, beetroot, red and yellow onion, orange and white carrots, watercress, broccoli, spinach, garlic, tomato and tamarillo, were determined. The methanolic extracts obtained from these matrices, was used to quantify the total content of the phenolic compounds, flavonoids, anthocyanins, betalains and carotenoids. The antioxidant capacity was also measured by three different methods: DPPH, ABTS and FRAP. The highest antioxidant capacity was determined for red onion, tamarillo and tomato. Using the QuEChERS extraction methodology combined with liquid chromatography of ultra-efficiency (UHPLC), it was possible to identify and quantify some polyphenols. Catechin and gentisic and ferulic acids were found the most abundant polyphenols. Additionally, the volatile composition of these samples was studied using solid phase microextraction (HS-SPME) followed by gas chromatography coupled to mass spectrometry (GC-MS). 320 volatile compounds were identified and grouped into different chemical families. Based on the results, terpenic compounds were found the most predominat group in beetroot (61%), orange carrot (58%) and white carrot (61%), while organosulfur compounds are dominant in onion, garlic and watercress. Regarding to broccoli and spinach, these vegetables are, essentially, constituted by alcohols and aldehydes, while fruits of Solanaceae family are characterized by esters, in tamarillo, and aldehydes in tomato.
Bioactive compounds are secondary metabolites that occur in small amounts in plants. In addition to acting as a defense system, these compounds also contribute to human well-being, due to its efficient antioxidant, anticancer, antimicrobial action, among others. In this work, the bioactive composition and antioxidant capacity of 11 vegetables samples typically consumed in RAM, namely, beetroot, red and yellow onion, orange and white carrots, watercress, broccoli, spinach, garlic, tomato and tamarillo, were determined. The methanolic extracts obtained from these matrices, was used to quantify the total content of the phenolic compounds, flavonoids, anthocyanins, betalains and carotenoids. The antioxidant capacity was also measured by three different methods: DPPH, ABTS and FRAP. The highest antioxidant capacity was determined for red onion, tamarillo and tomato. Using the QuEChERS extraction methodology combined with liquid chromatography of ultra-efficiency (UHPLC), it was possible to identify and quantify some polyphenols. Catechin and gentisic and ferulic acids were found the most abundant polyphenols. Additionally, the volatile composition of these samples was studied using solid phase microextraction (HS-SPME) followed by gas chromatography coupled to mass spectrometry (GC-MS). 320 volatile compounds were identified and grouped into different chemical families. Based on the results, terpenic compounds were found the most predominat group in beetroot (61%), orange carrot (58%) and white carrot (61%), while organosulfur compounds are dominant in onion, garlic and watercress. Regarding to broccoli and spinach, these vegetables are, essentially, constituted by alcohols and aldehydes, while fruits of Solanaceae family are characterized by esters, in tamarillo, and aldehydes in tomato.
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Keywords
Compostos bioativos Capacidade antioxidante Cromatografia líquida de ultra-eficiência Cromatografia gasosa acoplado a espetrometria de massa Madeira (Portugal) Bioactive compounds Antioxidant capacity Ultra-efficient liquid chromatography Gas chromatography coupled to mass spectrometry Bioquímica Aplicada . Faculdade de Ciências Exatas e da Engenharia