Histoquímica e prospecção de compostos produzidos por Senna alata (L.) Roxb. com potencial atividade alelopática

• Autor(a) principal: Rodrigues, Izabella Martins da Costa
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4491
• topic: Alelopatia; Produtos naturais; Ecologia química; Allelopathy; Natural produtcs; Chemical ecology; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

One of the most important aspects of allelopathy, in manipulated ecosystems, is its role in agriculture. Currently, the allelopathic potential of diverse species has been evaluated as one of the alternative control methods, reducing the intensive use of synthetic herbicides. In field observation of individuals of the specie Senna alata (L.) Roxb., was verified a rapid vegetative growth trending to form pure stands, and this is an evidence of allelopathy phenomenon. The study objective was the identification, by phytochemical tests, of the main compound classes of potential allelochemicals, found in this specie different structures; the evaluation of potential allelopathic and autotoxic activity of these structures extracts on the seeds germination and initial elongation of plants found in Amazon cultivated pastures; prospection of chemicals in the most allelopathic inhibitory active structure of S. alata; leaf anatomical studies and histochemical tests for the location and identification of the allelochemicals in the mesophyll cells. The plant material was collected from cultive in Experimental Field of Embrapa Amazônia Oriental, Belém, Pa, Brazil, dried and had been then submitted to exhaustive extraction with hydromethanolic solvent (3:7), by seven days, to obtain the crude extracts. In phytochemical tests were compared two different methodologies to determine the main classes of constituents potential allelochemicals of different structures (stems, flowers, leaves, roots, seeds and pods) from S. alata: tests by thinlayer chromatography (TLC), and tests to preliminary detection of distinct chemical constituents, based on their extraction with appropriate solvents and application of color testing. For the previous exam of its allelopathic and autotoxic potencial, hydromethanolics extracts of different fractions of S. alata were applied on the seed germination and radicle and hypocotyl elongation of two pastures weeds: Mimosa pudica and Senna obtusifolia, and one forage legume Pueraria phaseoloides, and Senna alata itself. For prospection, isolation and identification of present compounds in S. alata leaves and its allelopathic tests under: M. pudica, S. obtusifolia and S. alata, the crude extracts was fractioned through an adsorption chromatography column, and the most pures fractions were submitted to the Nuclear Magnetic Resonance Spectroscopy of hydrogen and carbon 13 to determine their structures. To the leaves anatomical and histochemical analyses usual techniques in plant anatomy were used. The phytochemical results of both methods demonstrated few similarities, and the TLC was the simplest, cheaper and faster. In this prime analysis, was comproved the high diversity of chemical compounds present in S. alata. In preliminary allelopathic and autotoxic tests, the results indicated that the major site of allelochemicals biosynthesis in S. alata, is found in their leaves, and the autotoxic effects of S. alata extracts are observed only in the early growth of seedlings, affecting mostly their root system. The most sensible specie, in general, was congener S. obtusifolia. Chemical investigation of S. alata leaves resulted on isolation, in the most polar fraction, of compounds belonged to the flavonoids glycosides class, which aromatic core were identified by NMR spectroscopic analysis as kaempferol. In alleopathic bioassays, the most sensible specie, was again S. obtusifolia, comproving the prelimirary results. Also, once and again S. alata showed to be more tolerant to the autotoxics effects of the fraction. And finally in the anatomical and histochemical trials, the leaves presented two forms of trichomes: tectors and glandulars. The principal characteristics of the specie were: amphiestomatic leaf, with paracytic stomata, dorsiventral mesophyll, and phenolic compounds presence. Leaves are rich in calcium oxalate crystals along their veins, and other phenolic compounds, such as flavonoids and anthraquinones, in different cells.