Senna alata is a weed species frequently found in pastures of the Amazonian region and whose leaves have medicinal properties. This study aimed to carry out a chemical prospecting and evaluation of the allelopathic activity of the compounds present in S. alata leaves. The plant material was dried, ground, and submitted to exhaustive extraction with water/methanol (3:7) solution. The crude extract obtained was fractioned by wet chromatography column. The purest fractions were submitted to Nuclear Magnetic Resonance Spectroscopy to determine their structures. To evaluate the effects of the isolated chemical substances, concentrations of 50, 100, 150 and 200 ppm were used in water/methanol solvents (3:7). The fractions were placed on Petri dishes and their effects were evaluated on seed germination and radicle and hypocotyl elongation of three pasture weeds: Mimosa pudica, Senna obtusifolia, and Senna alata itself. The compounds with allelopathic activity found in S. alata leaves belong to the flavonoid glycoside class, whose aromatic core is a kaempferol causing major inhibition on radicle elongation and germination of S. obtusifolia and M. pudica. The auto toxic effects of this compound are not very significant for seedling development and null for germination.
Leguminosae; allelochemicals; NMR; flavonoid glycosides; kaempferol
