Navegando por Assunto "Alelopatia"

Agora exibindo 1 - 18 de 18

Acesso aberto (Open Access)
Aleloquímico produzido pela gramínea forrageira Brachiaria humidicola
(2005-03) SOUZA FILHO, Antonio Pedro da Silva; PEREIRA, Angela Albertina Gaspar; BAYMA, Joaquim de Carvalho
The traditional methods of weed control in cultivated pasture do not meet society's present and future needs of protecting natural resources and life quality. An alternative to this problem could be the use of secondary metabolites produced by plants. These products present few risks to the environment and meet society interests. Therefore, this research was carried out to isolate, identify and characterize the allelopathic activity of chemical compounds produced by the forage grass Brachiaria humidicola. The allelopathic effects of the extracts, fractions and compound were tested on seed germination and root elongation of the weeds Mimosa pudica, Senna obtusifolia and Senna occidentalis. Germination bioassays were developed under 25 ºC and a photoperiod of 12 hours. For root elongation, the bioassay conditions were 25 ºC and photoperiod of 24 hours. Hydromethanolic extract was used as a source for isolating and identifying p-coumaric acid. The allelopathic effects were positively related to p-coumaric acid concentration, weed species and the evaluated parameter. Comparatively, S. occidentalis and M. pudica showed the greatest sensitivity to the allelopathic effects. For S. obtusifolia no allelopathic effects promoted by p-coumaric acid on seed germination or on root elongation could be detected under the concentration of 1.0 and 8.0 mg L-1. Root elongation was more sensitive to p-coumaric acid allelophatic effects than seed germination.
Acesso aberto (Open Access)
Análise comparativa do potencial alelopático do extrato hidroalcoólico e do óleo essencial de folhas de cipó-d'alho (Bignoniaceae)
(2009) SOUZA FILHO, Antonio Pedro da Silva; GUILHON, Giselle Maria Skelding Pinheiro; ZOGHBI, Maria das Graças Bichara; CUNHA, Roberto Lisboa
Allelopathy is an important mechanism that affects the stability of agro-eco systems. The identification of this character, in several cases, is accomplished via analysis of the effects of polar crude extracts. The allelopathic activity of the species "cipó-de-alho"(Mansoa standleyi - Bignoniaceae) is characterized in the present work, by comparing the effects of the hydroalcoholic extract and essential oil of the leaves, attempting to establish the need to consider in research of this nature the approach involving non polar extracts. Bioassays of the weed plant 'malicia'' (Mimosa pudica) radicle and hypocotyl germination and growth were carried out in periods of 10 days, using concentrations of 0.5%; 1.0% and 2.0%. The chemical constituents of the essential oil were also identified. The results showed that both the hydroalcoholic extract and the essential oil have the potential to inhibit radicle and hypocotyl germination and growth. The hydroalcoholic extract showed higher potential to inhibit germination, while the essential oil promoted more intense inhibitions on radicle and hypocotyl growth. The effects were positively related with concentration, with maximum and minimum effects being obtained at concentrations of 2.0% and 0.5%, respectively. The sulfur compounds diallyl disulfide (42.15) and diallyl trisulfide (11.25%), alone or in association, are involved with the allelophatic effects caused by the essential oil. In addition, the results point to the need to consider using non polar extracts when evaluating the allelopathic activity of a given plant, especially when there is no information about the production of essential oil by the prospected plant.
Acesso aberto (Open Access)
Análise comparativa dos efeitos alelopáticos das substâncias químicas titonina e titonina acetilada
(2006-06) SOUZA FILHO, Antonio Pedro da Silva; BORGES, Fábio Cardoso; SANTOS, Lourivaldo da Silva
The objective of this paper was to establish the variations in the allelopathic activity of the chemical substance tithonine, in function of the acetylation of its molecule. Germination bioassays, under 25 ºC of constant temperature and 12-hour photoperiod, and radicle and hypocotyl development bioassays under 25 °C of constant temperature and 24-hour photoperiod were developed. The receiving plant used was the weed Mimosa pudica. Spectral analysis RMN 1H and 13C and bidimensional RMN techniques were carried out on the acetylated molecule. The acetylation process produced the molecule 7,4'- dimethoxy-3'-acetylflavone, which differed from the original molecule, identified as 7,4'-dimethoxy-3'-hydroxyflavone. The structure of the acetylated tithonine was confirmed by the specters of RMN 1H, 13C, DEPT, COSY and HETCOR. Tithonine was acetylated with acetic anhydride in pyridine. The comparative analysis of the allelopathic activity of the two substances showed that acetylated tithonine presented a greater potential to inhibit seed germination, as well as root and hypocotyl development of M. pudica. Both tithonine and acetylated tithonine showed the same behavior pattern in relation to substance concentration. The data obtained allow suggesting the possibility of increasing the biological activity of a chemical substance with allelopathic activity without compromising its biological peculiarities, desirable to nature and to the interests of society.
Acesso aberto (Open Access)
Atividade alelopática de chalcona sintética, de seus precursores e de cetonas e aldeídos relacionados
(2007-12) BITENCOURT, Heriberto Rodrigues; SANTOS, Lourivaldo da Silva; SOUZA FILHO, Antonio Pedro da Silva
Several secondary metabolites produced by plants can be used as herbicides. These products are expected to offer fewer risks to the environment and to meet social demands. However, the availability of compounds is very limited, so synthesis is an alternative. The objective of this work was to evaluate the allelopathic activity of synthetic chalcone, 2,4'-dimethoxychalcone, its precursors, 4-methoxyacetophenone (A) and ortho-anisaldehyde (B), and some of their chemical alterations. The bioassays were developed under 25 ºC and photoperiod of 12 hours. The allelopathic effects of the compounds were tested on seed germination of Mimosa pudica and Senna obtusifolia weeds, under a concentration of 100, 200 and 300 mg L-1 of the compounds. The results indicated that precursor A (4-methoxyacetophenone) plays an important role in allelopathic activity of the chalcones. These results show that synthesis is a possible pathway, helping to overcome problems such as characterization and isolation of natural products with herbicidal activity against weed species.
Acesso aberto (Open Access)
Atividade alelopática de substâncias químicas isoladas da Acacia mangium e suas variações em função do PH
(2010) LUZ, Sylmara de Melo; SOUZA FILHO, Antonio Pedro da Silva; GUILHON, Giselle Maria Skelding Pinheiro; VILHENA, Karyme do Socorro de Souza
The aim of this study was to isolate, identify and characterize the allelopathic activity of the substances produced by Acacia mangium and to determine the variations of this activity according to the pH variation of the solution. The allelopathic activity was evaluated in germination bioassays (at 25 oC and under 12-12 h light-dark cycle) and radicle and hypocotyl development (at 25 oC and under 24-24 h light-dark cycle) of the weed species malicia (Mimosa pudica) and mata-pasto (Senna obtusifolia). The influence of the pH (3.0 and 9.0) of the solution in the allelopathic activity of the substances on seed germination of the same species was evaluated. The triterpenoids Lupenone (3 oxolup-20(29)-ene) and Lupeol (3β-hydroxylup-20(29)-ene), obtained from fallen leaves of the donor plant, separately and in pair, showed low allelopathic effects on seed germination and hypocotyl growth, especially on the former, with effects showing values lower than 2%. The effects on radicle growth were higher than the other two, reaching values above 40%, especially inhibition promoted by the substance Lupenone. Separately, each substance showed higher effects than those observed when tested in pair, indicating the existence of antagonism. The pH of the solution influenced the allelopathic activity of the substances; for Lupenone, the effects were more intense at acidic pH, while for Lupeol, best results were observed under alkaline conditions, showing that this is an important factor to be considered in field works.
Acesso aberto (Open Access)
Atividade alelopática de substâncias químicas isoladas do Capim-Marandu e suas variações em função do pH
(2008) SANTOS, Lourivaldo da Silva; SANTOS, Josiane Cristina Lucas dos; SOUZA FILHO, Antonio Pedro da Silva; CORRÊA, Marivaldo José Costa; VEIGA, Thiago Andre Moura; FERREIRA, Vivianne Cristinne Marinho Freitas; FERREIRA, Isabel Cristina Serrão; GONÇALVES, Nelson Santos; SILVA, Carlos E. da; GUILHON, Giselle Maria Skelding Pinheiro
This work aimed to isolate, identify and determine the allelopathic activity of the chemical substances produced by Brachiaria brizantha cv. Marandu and to verify the effects of the pH in the solution on the activity of these compounds. The allelopathic activity was evaluated based on germination bioassays and radicle and hypocotyl growth using the species 'malícia' (Mimosa pudica) and 'mata-pasto' (Senna obtusifolia) as receptors. The effect of pH was analyzed in a range from 3.0 to 9.0. The pentacyclic triterpenes friedelin and epifriefelinol isolated from the shoots of B. brizantha showed a low inhibitory activity against seed germination and radicle and hypocotyl growth of the two receptor plants evaluated. The pentacyclic triterpenes friedelin and epifrifelinol presented differentiated behaviors in relation to the pH variation in the solution, with stronger inhibition activity against the weed 'mata-pasto'.
Acesso aberto (Open Access)
Atividade alelopática em folhas de Tachigali myrmecophyla (Leg. - Pap.)
(2005-12) SOUZA FILHO, Antonio Pedro da Silva; LÔBO, Lívia Trindade; ARRUDA, Mara Silvia Pinheiro
The use of forest species with allelopathic activity can promote a higher stability to agroforestry systems, mainly relative to the reduction of weed species. The objective of this study was to isolate and identify chemical substances produced by Tachigali myrmecophyla and characterize its inhibitory allelopathic activity on the germination and seedling development of two weed species. Bioassays were carried out under controlled conditions of 25 ºC and 12-hour photoperiod for germination and 24-hour photoperiod for radicle and hypocotyl development. The extracts and fractions were analyzed under concentrations of 1.0% and 0.5%, and the substance under concentrations of 5, 10, 15 and 20 ppm. The isolation process allowed the identification of the chemical substance 4,5-dihydroblumenol A. This substance showed allelopathic activity, with the effects varying according to concentration, weed species and the plant parameter analyzed. The intensity of the allelopathic effects was positively associated to the concentration. Mimosa pudica was the most affected weed species. Radicle development was more sensitive plant to the substance effects than hypocotyl development and seedling germination.
Acesso aberto (Open Access)
Atividade potencialmente alelopática do óleo essencial de Ocimum americanum
(2009) SOUZA FILHO, Antonio Pedro da Silva; BAYMA, Joaquim de Carvalho; GUILHON, Giselle Maria Skelding Pinheiro; ZOGHBI, Maria das Graças Bichara
Essential oils are known for their several biological activities. The biodiversity of the Amazon region is rich in essential-oil producing plants.The aim of this work was to study the potentially allelopathic activity of the essential oil of Ocimum americanum and to determine its effects on seed germination and growth of two weed species. Solutions of the essential oil were tested at concentrations varying from 100 to 2,000 mg L-1, considering their effects on seed germination (at 25 ºC and a photoperiod of 12 hours) and radicle and hypocotyl growth (at 25 ºC and a photoperiod of 24 hours) of the weeds Mimosa pudica and Senna obtusifolia. Factors related to concentration, specificity of the receiving plants and the parameters analyzed were decisive for the effects obtained. Overall, there was a positive relation between concentration and inhibitory effect. M. pudica tended to be more sensitive to the effects than S. obtusifolia. Seed germination was more affected by the essential oil, followed by radicle elongation and hypocotyl elongation. The observed effects can be attributed to the composition of the essential oil, that includes monoterpenes, sesquiterpenes, aliphatic compounds and phenylpropanoids. The compounds limonene, camphor and linalol, found in the essential oil, are known to have allelopathic activity.
Acesso aberto (Open Access)
Bioensaios de atividade alelopática dos esteroides espinasterol, espinasterona e glicopiranosil espinasterol
(2012-12) RIPARDO FILHO, Haroldo da Silva; PACHECO, Luidi Cardoso; SOUZA FILHO, Antonio Pedro da Silva; GUILHON, Giselle Maria Skelding Pinheiro; ARRUDA, Mara Silvia Pinheiro; SANTOS, Lourivaldo da Silva
Three steroids (spinasterol, spinasterone, and spinasterol glucopyranosyl) were isolated from the stem of the Amazonian plant Moutabea guianensis. Their structures were determined on the basis of NMR analysis and by comparison with spectroscopic data found in the literature. The allelopathic activities of the three substances were evaluated against two common weeds of the Amazon region, Mimosa pudica ('malicia') and Senna obtusifolia ('mata-pasto'). The substance spinasterol glucopyranosyl was the most active in the radicle growth bioassay, inhibiting Senna obtusifolia in 75%; spinasterol inhibited the development of hypocotyl of Senna obtusifolia in 22%, and spinasterone and spinasterol inhibited 10% of the seed germination of the species Mimosa pudica. These results showed that the difference of substitutes at the C-3 position of the steroids can influence allelopathic activity: the glicosyl group at the C-3 position enhanced the inhibition of hypocotyl growth of the species Mimosa pudica, compared to the hydroxilated and carbonylated steroid. This is the first chemical and allelopathic study with Moutabea guianensis.
Acesso aberto (Open Access)
Dihydroflavonols from the leaves of Derris urucu (Leguminosae): structural elucidation and DPPH radical-scavenging activity
(2009) LÔBO, Lívia Trindade; SILVA, Geilson Alcantara da; FERREIRA, Malisson; SILVA, Milton Nascimento da; SANTOS, Alberdan Silva; ARRUDA, Alberto Cardoso; GUILHON, Giselle Maria Skelding Pinheiro; SANTOS, Lourivaldo da Silva; BORGES, Rosivaldo dos Santos; ARRUDA, Mara Silvia Pinheiro
Derris urucu is an Amazonian plant with insecticide and ichthyotoxic properties. Studies with this species show the presence of flavonoids, mainly rotenoids, as well as stilbenes. The ethanol extract of the leaves of Derris urucu (Leguminosae) afforded three new dihydroflavonols named urucuol A (1), B (2) and C (3), and the dihydroflavonol isotirumalin (4). Their structures were elucidated by extensive analysis of 1D and 2D NMR, UV and IR spectra and MS data and comparison with literature data. The isolated compounds (1-4) were evaluated for DPPH• radical scavenging activity and showed a relatively lower antioxidant ability compared to the commercial antioxidant trans-resveratrol.
Acesso aberto (Open Access)
Flavonoids from leaves of Derris urucu: assessment of potential effects on seed germination and development of weeds
(2013-09) SILVA, Ewerton Afonso Silva da; LÔBO, Lívia Trindade; SILVA, Geilson Alcantara da; SOUZA FILHO, Antonio Pedro da Silva; SILVA, Milton Nascimento da; ARRUDA, Alberto Cardoso; GUILHON, Giselle Maria Skelding Pinheiro; SANTOS, Lourivaldo da Silva; ARRUDA, Mara Silvia Pinheiro
In some previous studies, we described the isolation of nine compounds from leaves of Derris urucu, a species found widely in the Amazon rainforest, identified as five stilbenes and four dihydroflavonols. In this work, three of these dihydroflavonols [urucuol A (1), urucuol B (2) and isotirumalin (3)] were evaluated to identify their potential as allelochemicals, and we are also reporting the isolation and structural determination of a new flavonoid [5,3′-dihydroxy-4′-methoxy-(7,6:5″,6″)-2″,2″-dimethylpyranoflavanone (4)]. We investigated the effects of the dihydroflavonols 1-3 on seed germination and radicle and hypocotyl growth of the weed Mimosa pudica, using solutions at 150 mg.L–1. Urucuol B, alone, was the substance with the greatest potential to inhibit seed germination (26%), while isotirumalin showed greater ability to reduce the development of the hypocotyl (25%), but none of the three substances showed the potential to inhibit radicle. When combined in pairs, the substances showed synergism for the development of root and hypocotyl and effects on seed germination that could be attributed to antagonism. When tested separately, the trend has become more intense effects on seed germination, while for the substances tested in pairs, the intensity of the effect was greater on development of weed.
Acesso aberto (Open Access)
Investigação de metabólitos secundários de folhas de Derris urucu (Killip et Smith) Macbr. com atividades biológicas
(Universidade Federal do Pará, 2009-06-30) LÔBO, Lívia Trindade; SILVA, Milton Nascimento da; http://lattes.cnpq.br/6742390457977989; ARRUDA, Mara Silvia Pinheiro; http://lattes.cnpq.br/8047078292358267
Derris urucu, belonging to the family Leguminosae / Fabaceae, is popularly known as “timbó”. The roots of this species are commonly used as pesticides and poison to fish. From Derris genus many phytochemical studies have been reported, the roots being of the most studied part from the plants of this genus. The name “timbó” is most general for the species Derris urucu and Derris nicou, which are the species that produce, in their roots, rotenoids such as rotenone and deguelin, from which derives the importance of these plants. The extracts, and the substances isolated from this genus are responsible for a wide range of biological activities, mainly the insecticidal activity. From the ethanolic extract of leaves of D. urucu, twelve compounds were isolated and purified by High Performance Liquid Chromatography: five stilbenes, six dihydroflavonols and one flavanone. The structural identification was based on the mass, 1H and 13C NMR spectrometric analysis and two dimensional NMR, beyond comparison with literature data . The ethanolic extract of leaves of D. urucu was submitted to bioassays to avaluate the allelophatic potential, presenting relevant percentage of inhibition of seed germination and development of weeds in pastures. Aiming to detect the substances responsible for allelophatic activity, three stilbenes and three dihydroflavonols were selected and submitted to bioassays of inhibition of germination and development of the radicle and hypocotyl of weeds. The allelophatic tests were performed with the substances isolated and with the combination of them, aiming to assess the synergism between them, but the magnitude of inhibition observed was very low. By other side, when the substances were tested in mixtures there was a significant increase in the percentage of inhibition, so these substances in mixtures, can be considered promising for future studies involving allelophatic activity. An other test was carried out with the isolated compounds. Three stilbenes and five dihydroflavonols were evaluated for DPPH radical scavenging activity (antioxidant activity). In this bioassay, was not observed a significant antioxidant activity, justified by the analysis in the structures of the substances tested.
Acesso aberto (Open Access)
Metodologias empregadas em estudos de avaliação da atividade alelopática em condições de laboratório: revisão crítica
(2010) SOUZA FILHO, Antonio Pedro da Silva; GUILHON, Giselle Maria Skelding Pinheiro; SANTOS, Lourivaldo da Silva
During the last decades, many allelopathy research groups have been formed, worldwide. As part of this trend, Brazil has published a large number of scientific articles in national and international periodicals. Allelopathy, a relatively new science, is in its first stage of development; thus, a proliferation of often not very sound techniques has occurred. The use of such techniques makes it difficult to interpret the results, their biological value and real meaning. Procedures must become more uniform, as the importance of allelopathy increases. Thus, this work has critically revised the bioassay protocols used to characterize the allelopathic properties of crude extracts and pure substances, presenting the strong points and limitations of each procedure, as well.
Acesso aberto (Open Access)
Obtenção de extratos da polpa de açaí (Euterpe oleracea) por extração supercrítica: isotermas de rendimento global, atividade alelopática dos extratos, enriquecimento de antocianinas e compostos fenólicos
(Universidade Federal do Pará, 2016-10-04) BATISTA, Camila de Cássia Rodrigues; MACHADO, Nélio Teixeira; http://lattes.cnpq.br/5698208558551065; CARVALHO JUNIOR, Raul Nunes de; http://lattes.cnpq.br/5544305606838748
Açaí is one of the most popular functional foods of the Amazon, widely consumed in Brazil and became known in other countries, especially due to the many benefits it has for a wide use in the growing market for nutraceuticals. Açaí extracts derived have a number of components with antioxidant, vasodilatory, anti-inflammatory and energy. Among the appropriate technologies in the processes, supercritical technology has become advantageous to obtain extracts with higher quality, adding value to products and by-products of the process. This work presents as objective a study of the supercritical extraction process of acai pulp to obtain extracts rich in bioactive compounds. A evaluation of the variables of the supercritical extraction process with CO2 (temperature, pressure, and solvent density) of Açai pulp showed the conditions that maximize the amount extracts (lipid fraction) obtained, and enable the concentration anthocyanins in açai pulp defatted for subsequent extraction of these compounds. The extracts obtained from extraction with CO2 were evaluated for fatty acid composition and allelopathic activities. The overall yield isotherms showed that the maximum amount of extract obtained in the process was in the condition of 70°C/490 bar followed by the condition of 50°C/350 bar.
Acesso aberto (Open Access)
Phytotoxic potential of the geopropolis extracts of the jandaira stingless bee (Melipona Subnitida) in weeds
(Universidade Federal do Pará, 2017-12) PEREIRA, Daniel Santiago; HOLANDA NETO, João Paulo de; OLIVEIRA, Mozaniel Santana de; PEREIRA, Natanael Santiago; MARACAJÁ, Patrício Borges; SOUZA FILHO, Antonio Pedro da Silva
The objective of the present research is to characterize the phytotoxic activity of geopropolis from the Jandaira bee (Melipona subnitida Ducke) in the state of Ceará in Northeast Brazil and to analyze its effects. Extracts were prepared in 80% v/v grain alcohol at 0.25, 0.5, 0.75, and 1.0%. Their effects were determined on seed germination, radicle elongation, and hypocotyl growth of the pasture weeds malícia (Mimosa pudica) and mata-pasto (Senna obtusifolia). Extract phytotoxicity varied as functions of plant species, application dosage, and plant organ. M. pudica was more sensitive to the inhibitory effects of geopropolis than S. obtusifolia. There was a phytotoxic effect of 50% (PE50) for S. obtusifolia in terms of seed germination and in rootlet development near the maximum applied concentrations. M. pudica had PE50 and PE90 at the minimum concentration (0.25%) and near the maximum (1.00%), respectively. Thus, geopropolis extracts from the Jandaira bee (M. subnitida) are potentially phytotoxic to certain plant species.
Acesso aberto (Open Access)
Potencial alelopático de catequinas de Tachigali myrmecophyla (leguminosae)
(2008) LÔBO, Lívia Trindade; CASTRO, Kelly Christina Ferreira; ARRUDA, Mara Silvia Pinheiro; SILVA, Milton Nascimento da; ARRUDA, Alberto Cardoso; MÜLLER, Adolfo Henrique; GUILHON, Giselle Maria Skelding Pinheiro; SANTOS, Alberdan Silva; SOUZA FILHO, Antonio Pedro da Silva
Two compounds, (+)-catechin and epicatechin, were isolated from leaves of T. myrmecophyla, using chromatographic techniques. The structural identification was carried out on the basis of 1H and 13C NMR spectral data and comparison with literature data. The compounds (+)-catechin and epicatechin were submitted to germination inhibition and radicle and hypocotyl growth assays. Results showed some significant activities confirming the initial hypothesis about allelopathic properties of that plant.
Acesso aberto (Open Access)
Potencial alelopático de duas neolignanas isoladas de folhas de Virola surinamensis (Myristicaceae)
(2007-03) BORGES, Fábio Cardoso; SANTOS, Lourivaldo da Silva; CORRÊA, Marivaldo José Costa; OLIVEIRA, Marilene Nunes; SOUZA FILHO, Antonio Pedro da Silva
The objective of this research was to isolate, identify and characterize the allelopathic activity of chemical compounds in Virola surinamensis leaves. The process of isolation and identification of chemicals compounds involved the use of organic solvents and Magnetic Nuclear Resonance (MNR 1H, MNR 13C and MNR 13C-DPT), HETCOR and COSY specter. Allelopathic activity was evaluated by bioassays, under constant temperature of 25 ºC and 12-h photoperiod for seed germination and 25 ºC of constant temperature and 24-hour photoperiod for radicle and hypocotyl elongation, at concentrations ranging from 1.0 mg L-1 to 8.0 mg L-1. The receiving plants used were the weeds Mimosa pudica, Senna obtusifolia and Senna occidentalis. Two neolignans were isolated and identified: surinamensin and virolin. The general trend observed was a positive relation between allelopathic effects and the concentration of the compounds, with maximum inhibition obtained at the concentration of 8.0 mg L-1. Surinamensin presented greater potential to inhibit seed germination and radicle/hypocotyl elongation than virolin, regardless of the receiving species or plant parameter. Radicle and hypocotyl elongation were more intensely inhibited than seed germination by the two compounds. Except for the effects promoted on hypocotyl elongation, the species M. pudicawas the most sensitive to the allelopathic effects caused by the two neolignans.
Acesso aberto (Open Access)
Stilbenes from Deguelia rufescens var. urucu (Ducke) A. M. G. Azevedo leaves: effects on seed germination and plant growth
(2010) LÔBO, Lívia Trindade; SILVA, Geilson Alcantara da; FREITAS, Manolo Cleiton Costa de; SOUZA FILHO, Antonio Pedro da Silva; SILVA, Milton Nascimento da; ARRUDA, Alberto Cardoso; GUILHON, Giselle Maria Skelding Pinheiro; SANTOS, Lourivaldo da Silva; SANTOS, Alberdan Silva; ARRUDA, Mara Silvia Pinheiro
The Amazon biodiversity may provide plants whose chemical substances are capable of controlling weeds. In this study we report the isolation and identification of five stilbenes from the leaves of "timbó vermelho" (Deguelia rufescens var. urucu): 4-methoxylonchocarpene (1); 3,5-dimethoxy-4´-hydroxy-3´-prenyl-trans-stilbene (2), lonchocarpene (3), 3,5-dimethoxy-4´-O-prenyl-trans-stilbene (4) and pterostilbene (5). Compounds 2 and 4 are new natural products although 2 has been previously cited as synthesis product. Potential allelopathic activity for 1, 2 and 4 was evaluated over seed germination and plant growth of Mimosa pudica weed. The observed effects on seed germination did not vary significantly (p > 0.05) when the analysis of phytotoxicity was performed with the substances alone, the maximum inhibition did not exceed 20%. The most intense inhibitions on radicle and hypocotyl development were found for compound 4 (p < 0.05). When tested in pairs, showed antagonism for seed germination and synergism for radicle and hypocotyl development.