Estudo fitoquímico de Annona sylvatica (Annonaceae). Avaliação das atividades inseticida e fungicida frente às formigas cortadeiras e seu fungo simbionte e ao gorgulho do milho

Abstract

The leaf-cutting ants are social species, living in permanent colonies. The genera of the greater importance, Atta (saúvas) and Acromyrmex (quenquéns), are the major plagues of Brazilian agriculture, to cause serious damages by its large and uncontrolled grazing, which leads to serious economic losses for many agrosystems. In the same way, the corn maize weevil, Sitophilus zeamais, belonging to the family Curculionidae, is the major pest species of stored corn. The corn grains are drilled and damaged by larvae and adults, causing numerous qualitative and quantitative losses of corn grains disabling its marketing. As the consequence, the effective control of these plagues is extremely important for agriculture and economy that aims to provide the nacional and international market quality products with high commercial value. In this context, the phytochemistry study of Annona sylvatica provides an alternative way to control these plagues, since that studies of these species showed a wide variety of natural products with promising activities, including, insecticide and fungicide, due to the large presence of acetogenins and lignans as secondary metabolites. This study allowed the isolation of fourteen compounds (four lignans, four acetogenins, three alkaloids and three steroids), however were identified eleven compounds due to the high structural complexity presented for the acetogenins. The identification techniques employed have been using single and two-dimensional spectra of 1H and 13C NMR and Mass Spectrometry (HPLC/NMR; HPLC/ESI-MS/MS e HPLC/APCI-MS/MS). For the biological tests, the ethanolic extract of the seeds stood out as potentially toxic to three bioassays cited above. The leaves and branches dichlorometanic fractions obtained by liquid-liquid partitioning of the extracts were toxic for leaf-cutting ants and their symbiotic fungus. Among the acetogenins isolated, only one of them showed a significant activity against corn maize weevil.