Avaliação do efeito do extrato e de frações proteicas das sementes de Crotalaria stipularia (Desv., 1814) (Farbales: Fabaceae) sobre a sobrevivência e parâmetros nutricionais de Tribolium castaneum (HERBST, 1797) (Coleoptera: Tenebrionidae)

Abstract

The reddish-brown beetle, Tribolium castaneum (Coleoptera: Tenebrionidae), is one of the insect pest of stored grains that further damages the storage product industry.To control this pest, pesticides are mainly used. However, insect resistance and the high toxicity of these compounds to the environment and non-target organisms have led to an increase in the search for toxicity-free and effective natural products to control pest insects. Extracts and lectins (proteins or glycoproteins that recognize carbohydrates and agglutinate cells) isolated from plants have shown insecticidal activity and for this reason have been well studied. Crotalaria stipularia, Fabaceae, are wide y distributied in environments of Atlantic Forest being important in the bovine as food for. Thus, the objective of this study was to analyze the insecticidal activity of the extract and lectin fractions of C. stipularia seeds on adult insects of T. castaneum. These are, the crude extract was prepared in 50 mM Tris-HCl, pH 8.0 of the plant seeds, followed by saline precipitation with ammonium sulfate. Subsequently, extract and fraction were quantified usms the Bradford method and evaluated for the presence of lectins. Then, solutions of different concentrations were prepared for the extract (2%, 5% and 10% w/v) and for the fraction (0.5%, 1%, 2% and 5% w/v). The insecticidal activity of the extract and fraction, the dietary determination, the nutritional parameters of the treated insects, the effects of the extract and lectin on the reproduction of these insects were evaluated, besides the biochemical profile presented by them after the 28 days of the test. The extract (10% w/v) of C. stipularia caused 100% mortality of T. castaneum insects, also presenting a deterrent activity (10% w/v), besides exerting antinutritional effects, affecting reproduction and interfering in the metabolism of proteins, cholesterol, triglycerides and carbohydrates of the treated insects. On the other hand, the protein fraction 20% caused mortality of the insects to a lesser extent than the extract, revealing that mortality may also be associated with other metabolites present in the extract and absent in the fraction or the synergy between them. Unlike the extract, the fraction did not present deterrent activity, however it affected in the nutritional parameters of the insect, besides altering the reproduction and the metabolism. In this way, seeds of C. stipularia are a biomaterial with potential to be used in the control of T. castaneum.