Avaliação da atividade antioxidante e alelopática do extrato etanólico e frações das cascas do caule de Zanthoxylum rhoifolium Lam., Rutaceae / Assessment of antioxidant and allelopathic activities of ethanolic extract and solvent fractions from stem bark of Zanthoxylum rhoifolium Lam. (Rutaceae)

The purpose of this study was to test for antioxidantand allelopathic activities in stem bark of Zanthoxylum rhoifolium Lam., Rutaceae, with the eventual aim of discovering biologically active substances. The plant material was subjected to ethanolic extraction and this extract was partitioned, yielding hexane, chloroform, ethyl acetate and hydroalcoholic fractions. Antioxidant activity was estimated by the reduction of phosphomolybdenum complex, of DPPH. and of thiobarbituric acid-reactive substances (TBARS). To detect allelopathy, the samples were tested, at four concentrations, on the germination and development of the radicle and hypocotyl of L. sativa seeds. The samples showed significant antioxidant activity against the reduction of the phosphomolybdenum complex, as compared to rutin, and reduction of TBARS, ascompared to BHT, as well as allelopathic activity, since they stimulated growth and seed germination. The chloroform and ethyl acetate fractions showed the best antioxidant potentials, with 204.17% and 127.11% compared to rutin, in the reduction of phosphomolybdenum complex, as did the crude ethanolic extract and hexane fraction, with 64.2% and 60.9% compared to BHT, in the TBARS method. In the allelopathic assay, the chloroform fraction stood out as the only sample that stimulated the growth of both the radicle and hypocotyl at most concentrations, ranging from 41 to 144%, while the ethyl acetate fraction achieved the greatest stimulus in this bioassay, increasing the growth of the hypocotyl by 274%. This is the first study that demonstrates the antioxidant and allelopathic activities of the species Z. rhoifolium...

Este trabalho teve como objetivo o estudo das atividades antioxidante e alelopática das cascas do caule de Zanthoxylum rhoifolium Lam., Rutaceae, de modo a conduzir à descoberta de substâncias biologicamente ativas. O material vegetal foi submetido à extração etanólica e este extrato foi fracionado obtendo as frações (hexano, clorofórmio, acetato de etila e hidroalcoólica). Para a avaliação da atividade antioxidante, empregaram-se os métodos de redução do complexo fosfomolibdênio, de redução do radical DPPH e das substâncias reativas ao acido tiobarbitúrico (TBARS). Quanto à alelopatia, as amostras foram testadas em quatro concentrações sobre a germinação e o desenvolvimento de radícula e hipocótilo das sementes de Lactuca sativa. As amostras evidenciaram atividade antioxidante significativa frente ao método de redução do complexo fosfomolibdênio quando comparada à rutina, e do TBARS quando comparado ao BHT, assim como a atividade alelopática, uma vez que estimularam tanto a germinação como o crescimento das sementes. A fração clorofórmica e acetato de etila demonstraram melhor potencial antioxidante com 204,17% e 127,11% em relação à rutina no método de formação do complexo fosfomolibdênio, e o extrato bruto e a fração hexano com 64,2% e 60,9%, em relação ao BHT, no método TBARS. No ensaio alelopático, destaca-se a fração clorofórmica, pois foi a única amostra que estimulou o crescimento do hipocótilo e radícula na maioria das concentrações, variando de 41 a 144%, e a fração acetato de etila que apresentou a maior porcentagem de estímulo nesse bioensaio, demonstrando estímulo de 274% do crescimento do hipocótilo. Este é o primeiro trabalho que demonstra a atividade antioxidante e alelopática de Z. rhoifolium...

Protective effect of hop beta-acids on microbial degradation of thick juice during storage.

AIMS: This study assessed the value of a commercial alkaline solution of hop beta-acids (HBA) for prevention of microbial degradation of thick juice, a concentrated intermediate product in the production of beet sugar. METHODS AND RESULTS: The antimicrobial effect of different concentrations of HBA against microbial degradation of thick juice was tested in a pilot-scale storage experiment. Chemical, biochemical and microbial parameters were monitored during thick juice storage. Thick juice degradation, indicated as a decrease in pH, was generally accompanied by an increase in the count of fastidious bacteria (FB) on Columbia Agar with Sheep Blood (CAwSB), which were mainly identified as Tetragenococcus halophilus. Addition of HBA delayed juice acidification and the development of FB in a concentration-dependent manner. The susceptibility of FB to HBA was determined by plating degraded thick juice (FB > 10(5) CFU ml(-1) on CAwSB plates with different concentrations of HBA (0-160 ppm). None of the HBA concentrations tested reduced the number of FB colonies formed, but increasing HBA concentrations extended the lag time of colony formation. CONCLUSIONS: HBA produce no measurable bactericidal effect, but retard the development of FB in thick juice. Moreover, HBA do not prevent the thick juice from deteriorating, but significantly delay its degradation. SIGNIFICANCE AND IMPACT OF THE STUDY: These results indicate that adding a commercially available HBA formulation can prolong the storage life of thick juice in the sugar industry, although degradation cannot be eliminated. Future research will focus on the detailed characterization of FB consistently isolated from degraded thick juice and on determining their role in thick juice degradation.