RESUMO:Objetivou-se determinar o rendimento, a composição química e avaliar a atividade antilisterial dos óleos essenciais de Cymbopogon citratus (DC.) Stapf. (capim-limão) e Cymbopogon nardus (L.) Rendle (capim-citronela), puros e em combinação. A obtenção dos óleos essenciais foi realizada a partir de folhas frescas, empregando-se a técnica de hidrodestilação e utilizandose aparelho de Clevenger modificado. Os rendimentos foram calculados a partir da massa obtida na extração e da umidade do material vegetal. A análise qualitativa foi realizada por cromatografia em fase gasosa acoplada à espectrometria de massas e a avaliação dos teores dos constituintes químicos por cromatografia em fase gasosa com detector de ionização de chamas. O efeito bacteriostático de diferentes concentrações dos óleos essenciais, puros e em combinação, foi determinado pela técnica de difusão em ágar. As concentrações mínimas inibitórias (CMIs) foram utilizadas na determinação do tempo de ação bactericida. O rendimento, em base seca, foi de 1,39% (v/p) para o óleo essencial de C. citratus e de 2,27% (v/p) para o óleo essencial de C. nardus. Geranial e neral foram os constituintes majoritários do óleo essencial de C. citratus, enquanto, para C. nardus, foram citronelal, geraniol e citronelol. A maioria das concentrações utilizadas mostrou-se efetiva contra Listeria monocytogenes e observaram-se efeitos bactericidas nas CMIs. Óleos essenciais de C. citratus e C. nardus, puros e em combinação, constituem novas alternativas de antibacterianos naturais a serem utilizados no controle de L. monocytogenes na indústria de alimentos. Palavras-chave: Cymbopogon citratus, Cymbopogon nardus, óleos essenciais, atividade antibacteriana, Listeria monocytogenes ABSTRACT: Yield, chemical composition and antilisterial activity of essential oils fromCymbopogon species. The aim of this study was to determine the yield and the chemical composition of essential oils from Cymbopogon citratus (DC.) Stapf. (lemongrass) and Cymbopogon nardus (L.) Rendle (citronella), and to evaluate their antilisterial activity when pure and combined. The essential oils were obtained from fresh leaves through hydrodistillation by using a modified Clevenger-type device. Yield was calculated based on the extracted mass and the plant humidity. The qualitative analysis was done by gas chromatography-mass spectrometry and the levels of the chemical components were detected by gas chromatography with flame ionization detector. The bacteriostatic effect of different concentrations of pure and combined essential oils was determined by the agar diffusion technique. Minimum inhibitory concentrations (MICs) were used to determine the time of bactericidal action. The yield was 1.39% (v w -1 dry basis) for C. citratus essential oil and 2.27% (v w -1 ) for C. nardus essential oil. Geranial and neral were the major components of C. citratus essential oil, while citronellal, geraniol and citronellol were predominant in C. nardus oil. Most of the used concentrations were efficient against Listeri...
The antibacterial eVects of Cinnamomum cassia essential oil (EO) and cinnamaldehyde were evaluated against single-and mixed-species cultivation of enteropathogenic Escherichia coli (EPEC) and Listeria monocytogenes attached to stainless steel. A central composite rotational design with two variables and eleven assays was used to optimize the concentrations (0.00-1.00% v/v for the EO and 0.00-0.80% v/v for cinnamaldehyde) and contact times (1-21 min). The models generated were validated, and the eVectiveness of C. cassia EO and cinnamaldehyde was compared with that of commercially available chemical sanitizers. Cinnamaldehyde and C. cassia EO proved to be eYcient alternatives to commercial chemical sanitizers in the reduction or elimination of sessile bacterial cells. The activity of these natural compounds was, in most cases, equivalent or superior to that of the chemical sanitizers tested. However, L. monocytogenes was more resistant than EPEC to C. cassia EO and cinnamaldehyde, and the bacterial association in mixed-species bioWlms made them more susceptible to these compounds.
-The objective of this work was to evaluate the effect of inclusion of dietary glycerol in replacement to starch on the growth and energy metabolism of Nile tilapia juveniles. The experiment was carried out in a completely randomized design with four treatments (0, 5, 10, and 15% purified glycerol) and six replicates. Pelleted, isonitrogenous, and isocaloric diets were provided for 60 days. Growth performance parameters and muscle glucose and protein concentrations were not affected by dietary glycerol levels. The treatment with 15% glycerol presented higher levels of muscle and liver triglycerides. A quadratic effect of treatments on muscle and liver triglyceride concentrations was observed. The treatment with 0% glycerol presented higher hepatic glucose levels than the one with 15%. Treatments did not differ for concentrations of liver protein, as well as of plasma glucose, triglycerides, and protein. Treatments with 10 and 15% glycerol showed higher activity of the glucose-6-phosphate-dehydrogenase enzyme than the treatment with 5%; however, there were no significant differences in the hepatic activities of the malic and glycerol kinase enzymes. A linear positive effect of treatments was observed on the activity of the glycerol kinase enzyme in liver. Levels of glycerol inclusion above 10% in the diet of Nile tilapia juveniles characterize it as a lipogenic nutrient.Index terms: Oreochromis niloticus, alternative feed, carbohydrate, nutrition. Crescimento e metabolismo energético de juvenis de tilápia-do-nilo alimentados com glicerolResumo -O objetivo deste trabalho foi avaliar o efeito da inclusão de glicerol na dieta, em substituição ao amido, sobre o desempenho e o metabolismo energético de juvenis de tilápia-do-nilo. O experimento foi conduzido em delineamento inteiramente casualizado com quatro tratamentos (0, 5, 10 e 15% de glicerol purificado) e seis repetições. Dietas peletizadas, isonitrogenadas e isoenergéticas foram fornecidas por 60 dias. Os parâmetros de desempenho produtivo e as concentrações de glicose e proteína muscular não foram afetados pelos níveis de glicerol na dieta. O tratamento com 15% de glicerol apresentou maiores níveis de triglicerídeos musculares e hepáticos. Observou-se efeito quadrático dos tratamentos nas concentrações de triglicerídeos no músculo e no fígado. O tratamento com 0% de glicerol apresentou maiores níveis de glicose hepática do que o tratamento com 15%. Os tratamentos não diferiram quanto às concentrações de proteína no fígado, bem como de glicose, triglicerídeos e proteína no plasma. Os tratamentos com 10 e 15% de glicerol apresentaram maiores atividades da enzima glicose-6-fosfato-desidrogenase do que o tratamento com 5%; no entanto, não houve diferenças significativas nas atividades hepáticas das enzimas málica e glicerol quinase. Observou-se efeito linear positivo dos tratamentos na atividade da enzima glicerol quinase no fígado. Níveis de inclusão de glicerol acima de 10% na dieta de juvenis de tilápia-do-nilo o caracterizam como nutriente lipogênico....
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