POTENCIAL FITOTÓXICO DE Pterodon polygalaeflorus BENTH (LEGUMINOSAE) SOBRE Acanthospermum australe (LOEFL.) O. KUNTZE E Senna occidentalis (L.) LINK

Abstract

The objectives of this research were synthesize and characterize the allelopatic activity of 6a,7bdi-hydroxyvouacapan-17b-oic acid derivatives, isolated from seeds of Pterodon polygalaeflorus Benth (Leguminosae). The compound characterization processes involve in infrared spectrometry (IR) and hydrogen and carbon nuclear magnetic resonance (1H and 13C NMR) including experiments in double dimensions (COSY 1H 1H, HMQC and HMBC). Allellopathic effects were evaluated by bioassays, carried out at controlled 25 °C temperature and photoperiod (12h light/12h dark), during 72 hours. Sample concentrations of 1,0, 100,0 and 1000,0 mg.L-1 were tested. Senna occidentalis (fedegoso) and Acanthospermum australe (carrapichinho) were used as the target weed plants. Was observed that the allelopatic effect of the compounds increased as a function of the enhancement of concentration, thus showing a relation dose dependence. The N-ethyl-6a-acethoxy- 7b-hydroxyvouacapan-17b-amide and N,N-diethyl-6a-acethoxy-7b-hydroxyvouacapan 17b-amide were the derivatives that present the biggest inhibitory effect on seed germination and root growth of fedegoso and carrapichinho. Therefore, these compounds represent the most allelochemical potential against these weeds.