Papers by Maria Augusta Machado
RESUMO-Este trabalho avaliou o potencial alelopático de extratos foliares e radiculares de Lafoen... more RESUMO-Este trabalho avaliou o potencial alelopático de extratos foliares e radiculares de Lafoensia glyptocarpa Koehne sobre a germinação de sementes e o crescimento de plântulas e de células do metaxilema de gergelim (Sesamum indicum L.). A partir dos resultados, verifi cou-se que os extratos de folhas e raízes de L. glyptocarpa causaram alterações na germinação das sementes e no crescimento das plântulas de gergelim, além de alterações na raiz primária e diminuição no tamanho e número de células do metaxilema. Foram também obtidos extratos foliares com hexano, diclorometano, acetato de etila, acetona e metanol, e testados sobre o desenvolvimento de coleóptilos de trigo, sendo que os quatro últimos apresentaram atividade. Com o sub-fracionamento do extrato de acetato de etila, que se apresentou como o mais promissor, cessou a atividade inibitória para as sub-frações, sendo posteriormente verifi cada a presença de sinergismo entre elas. Palavras-chave: alelopatia; Lafoensia glyptocarpa; Sesamum indicum, sinergismo ABSTRACT-Allelopathic effects of Lafoensia glyptocarpa Koehne on Sesamum indicum L. and on the growth of Triticum aestivum L. coleoptiles. This study evaluated the allelopathic potential of leaf and root extracts of Lafoensia glyptocarpa Koehne on seed germination and the growth of seedlings and sesame (Sesamum indicum L.) metaxylem cells. We found that the leaf and root extracts of L. glyptocarpa changed in sesame seed germination and seedling growth, as well as changes in the primary root and decreased size and number of metaxylem cells. Leaf extracts were also obtained with hexane, dichloromethane, ethyl acetate, acetone, and methanol, and tested when developing wheat coleoptiles, and the last four showed activity. By subfractioning the ethyl acetate extract, which was the most promising, inhibitory activity ceased for subfractions, and the presence of synergism was subsequently found between them.
Acta Scientiarum. Agronomy, 2013
Allelopathic substances can be used to develop weed control alternatives based on natural product... more Allelopathic substances can be used to develop weed control alternatives based on natural products. The objective of this study was to compare the phytotoxic activity of aqueous leaf extracts of Rapanea umbellata with the toxicity of a synthetic herbicide on the germination and growth of weed species. The weeds species barnyard grass (Echinochloa crus-galli), wild poinsettia (Euphorbia heterophylla) and morning glory (Ipomoea grandifolia) were used. The effects of the aqueous leaf extract of R. umbellata at concentrations of 10% and 5% (g mL-1) were compared to the control (distilled water) and to the synthetic herbicide oxyfluorfen. The average weed germination time was significantly lower (p < 0.05) in control than in extract and herbicide treatments. The herbicide had more significant effects than the extract on the initial growth of the aerial part. However, the initial growth of the root part was significantly more affected by the leaf extract than by the herbicide. The extract also caused many disorders in weed root anatomy. Therefore, the leaf aqueous extract of R. umbellata showed important results that indicate that it should be bioprospected and that its allelochemicals should be purified for the discovery of natural-origin herbicides.
Journal of Natural Products, 2015
Tithonia diversifolia (Mexican sunflower) is a dominant plant of the Asteraceae family, which sug... more Tithonia diversifolia (Mexican sunflower) is a dominant plant of the Asteraceae family, which suggests it produces allelochemicals that interfere with the development of surrounding plants. The study described herein was conducted to identify the compounds that have phytotoxic activity in T. diversifolia extracts. Ethyl acetate extracts of the leaves, stems, and roots showed significant inhibition of wheat coleoptile growth, and the leaf extract had similar inhibitory effects to a commercial herbicide. Fourteen compounds, 12 of which were sesquiterpene lactones, have been isolated. Two sesquiterpene lactones are reported for the first time and were isolated as an inseparable mixture of 8β-O-(2-methylbutyroyl)tirotundin (4) and 8β-O-(isovaleroyl)tirotundin ( ). Their structures were determined by spectroscopic analysis, including NMR techniques and mass spectrometry. The sesquiterpene lactones 1β-methoxydiversifolin (6), tagitinin A (7), and tagitinin C (8) were the major products identified. These compounds were active on etiolated wheat coleoptiles, seed germination, and the growth of STS and weeds. The phytotoxic activity shown by these sesquiterpene lactones indicates that they are the compounds responsible for the activity exhibited by the initial extracts.
Tithonia diversifolia (Mexican sunflower) is a dominant plant of the Asteraceae family, which sug... more Tithonia diversifolia (Mexican sunflower) is a dominant plant of the Asteraceae family, which suggests it produces allelochemicals that interfere with the development of surrounding plants. The study described herein was conducted to identify the compounds that have phytotoxic activity in T. diversifolia extracts. Ethyl acetate extracts of the leaves, stems, and roots showed significant inhibition of wheat coleoptile growth, and the leaf extract had similar inhibitory effects to a commercial herbicide. Fourteen compounds, 12 of which were sesquiterpene lactones, have been isolated. Two sesquiterpene lactones are reported for the first time and were isolated as an inseparable mixture of 8β-O-(2-methylbutyroyl)-tirotundin (4) and 8β-O-(isovaleroyl)tirotundin (5). Their structures were determined by spectroscopic analysis, including NM techniques and mass spectrometry. The sesquiterpene lactones 1β-methoxydiversifolin (6), tagitinin A (7), and tagitinin C (8) were the major products identified. These compounds were active on etiolated wheat coleoptiles, seed germination, and the growth of STS and weeds. The phytotoxic activity shown by these sesquiterpene lactones indicates that they are the compounds responsible for the activity exhibited by the initial extracts.
Recebido em 03.IX.2013. Aceito em 26.V.2014
Allelopathic substances can be used to develop weed control alternatives based on natural product... more Allelopathic substances can be used to develop weed control alternatives based on natural products. The objective of this study was to compare the phytotoxic activity of aqueous leaf extracts of Rapanea umbellata with the toxicity of a synthetic herbicide on the germination and growth of weed species. The weeds species barnyard grass (Echinochloa crus-galli), wild poinsettia (Euphorbia heterophylla) and morning glory (Ipomoea grandifolia) were used. The effects of the aqueous leaf extract of R. umbellata at concentrations of 10% and 5% (g mL -1 ) were compared to the control (distilled water) and to the synthetic herbicide oxyfluorfen. The average weed germination time was significantly lower (p < 0.05) in control than in extract and herbicide treatments. The herbicide had more significant effects than the extract on the initial growth of the aerial part. However, the initial growth of the root part was significantly more affected by the leaf extract than by the herbicide. The extract also caused many disorders in weed root anatomy. Therefore, the leaf aqueous extract of R. umbellata showed important results that indicate that it should be bioprospected and that its allelochemicals should be purified for the discovery of natural-origin herbicides.
Resumo -O objetivo deste trabalho foi comparar uma população de leveduras do filoplano de lírio d... more Resumo -O objetivo deste trabalho foi comparar uma população de leveduras do filoplano de lírio de um sistema convencional de cultivo com outra de sistema integrado, além de avaliar o antagonismo da levedura Sporidiobolus pararoseus a Botrytis cinerea. A comunidade de leveduras foi estimada pelo método da queda dos balistoporos nos terços inferior, médio e superior das plantas, bem como nas faces adaxial e abaxial das folhas. Nos discos de folhas de plantas do sistema integrado, foi alta a presença da população de leveduras, tendo sido maior na face adaxial das folhas do terço médio das plantas. Para avaliação do antagonismo, foram aplicadas aos discos de folhas as concentrações de 10 5 , 10 6 e 10 7 células mL -1 da levedura, em três períodos de inoculação: 24 horas antes; simultânea a; e 24 horas após a inoculação de 10 4 esporos mL -1 de B. cinerea. A incidência, a percentagem de área de discos colonizados e a esporulação de B. cinerea foram avaliadas por meio de diagrama de notas, a partir do quarto dia após a inoculação. Todas as concentrações da levedura reduziram a esporulação de B. cinerea nos discos de folha, em comparação à testemunha, e a concentração de 10 7 esporos mL -1 foi a mais eficiente.
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Papers by Maria Augusta Machado