RESUMO -(Bioprospecção de substâncias inseticidas de plantas nativas de Mato Grosso do Sul, Brasil Palavras-chave: metabólitos secundários, plantas inseticidas, gorgulho-do-milho, Sitophilus zeamaisABSTRACT -(Bioprospecting insecticidal compounds from plants native to Mato Grosso do Sul, Brazil). This paper reports on an evaluation of the insecticidal activity of extracts prepared from leaves of Tapirira guianensis Aubl. (Anacardiaceae), Attalea phalerata (Mart. ex Spreng.) Burret (Arecaceae), Eugenia uniflora L. (Myrtaceae), and Gomphrena elegans Mart. (Amaranthaceae) and from stems of Myracrodruon urundeuva Allemão (Anacardiaceae). Four extracts and 18 fractions with a range of polarities were tested. Tengram batches of wheat grains were each nebulized with 1 mL of a separate extract at 10% w/v. After solvent evaporation at 38 ºC, the grains were placed into flasks along with 20 unsexed 10-to 20-day old adult individuals of Sitophilus zeamais. The assessment was carried out on the fifth and tenth day by counting and discarding the dead insects. Leaf extracts of G. elegans showed an insecticidal effect ranging from 27% to 60% by the fifth day, whereas the effect of the remaining extracts tested (if active at all) did not exceed 20% in the same period. By the tenth day, the most active extracts were those of A. phalerata (hexanic, 36.5%) and all those of G. elegans (52-80.5%), whereas the effect of the other extracts did not exceed 30%.

Efeito Inseticida de Extratos de Plantas Nativas do Mato Grosso do PALAVRAS-CHAVE -Planta inseticida, Gomphrena elegans, biopesticida, gorgulho-do-milho, bioprospecção.ABSTRACT -Research on insecticidal plants has increased in recent years, as has their utilization. Their compatibility with other methods of insect control and their lower toxicity to mammals are some of the advantages that have fostered their use. In the present study, selected plant species native to the state of Mato Grosso do Sul, Brazil, were investigated for their insecticidal potential against Sitophilus zeamais Mots. The extracts assayed were obtained from stems of Tapirira guianensis Aubl. (Anacardiaceae), Schinus terebinthifolius Raddi (Anacardiaceae), Tabebuia heptaphylla (Vell.) Toledo (Bignoniaceae), and Gomphrena elegans Mart. (Amaranthaceae). Wheat grains were treated with the extracts and distributed into acrylic containers, each holding 20 unsexed 10-to 20-day-old S. zeamais adults. For the control the wheat grains were treated solely with solvents. The number of dead insects was counted daily until the tenth day. T. heptaphylla and G. elegans extracts exhibited insecticidal effect since the fifth day of treatment, whereas the effect of the other extracts was not observed before the tenth day. Insect death was caused by the following extracts: T. guianensis in n-butanol, hexane, and dichloromethane; S. terebinthifolius in ethanol, ethyl acetate, hexane, and dichloromethane; T. heptaphylla in acetonitrile-chloroform, ethanol, and hexane; and G. elegans in ethanol, hexane, dichloromethane, ethyl acetate, and as hydroalcoholic extract. G. elegans extracts had the strongest insecticidal effect of all the species tested.

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