Atividade inseticida do extrato metanólico de araucaria Angustifolia

Abstract

The studies of plants with insecticidal properties were reassumed after finding serious environmental pollution problems caused by misuse of chemicals, including organophosphate compounds. The use of plant substrates, as insecticides, has numerous advantages when compared with synthetic products: natural insecticides are made from renewable resources and are rapidly degraded (therefore, do not persist in the environment) and do not leave residues in foods, in addition to their low production cost. Araucaria angustifolia is a Brazilian tree specie and has a broad distribuition in southern Brazil. However, the huge exploitation put it on the official list of Brazilian flora species threatened of extinction. The objective of this work was to identify the mechanism of action involved in the insecticidal activity of the methanolic extract of Araucaria angustifolia leaves and the secondary(ies) metabolite(s) involved in this action, by using assayes of minimum lethal dose (MLD), cardiovascular, behavioral and neurolocomotor in Phoetalia pallida. The thin layer chromatography showed the presence of the flavonoid qrecetin in the methanolic extract of A. angustifolia. The MLD, after a period of 24 hours, was the dose of 10Ag/AL of A. angustifolia (n=6 p˂0,05). In preparation (SIHC) the extract did not induced significant changes in heart rate of the insect, when compared to control group, n=6. To the tests of neurolocomotor activity and central neurotoxicity “grooming”, the methanolic extract of A. angustifolia induced significant changes in behavioral patterns of the cockroach, when compared to control group (n=6 p<0.05) respectively. The transmission of nervous impulses in insects is mediated by biogenic monoamines such as dopamine (DA), octopamine and serotonin (5-HT) (Libersat, 2003). Since quercetin is a natural insecticide, we suggest that the lethal effect of A. angustifolia is quercetin-induced. Nevertheless, the increase in grooming and neurolocomotor patters and lack of cardiovascular effect, show that the insecticidal effect of A. angustifolia is associated with an effect in the nervous system rather than in the cardiocirculatory system.