Bioatividade de um inibidor de protease de sementes de Enterolobium ontortisiliquum (Vell.) Morong sobre o desenvolvimento do mosquito Aedes aegypti e sua microbiota intestinal

Abstract

Urban insects are considered barriers to human development acting as agricultural pests and disease vectors. Usually the chemicals used in controlling insects cause damage to the environment and the rising of resistant organisms. Thus, in the last decades there has been an increase interest in searching new natural molecules origin, such as protease inhibitors with safe and environmentally-friendly insecticidal activity. Thus, the present study aimed to assess the biological properties of a protease inhibitor of seeds from Enterolobium contortisiliquum (Vell.) Morong, a native plant of Caatinga. The crude protein extract (EcEB) of the defatted E. contortisiliquum flour was subjected to precipitation with trichloroacetic acid (TCA) 20% to a final concentration of 5% (F5). Subsequently, F5 was applied to ion-exchange chromatography column to remove the peak P200 eluted with Tris-HCl 50mM pH 7.5 buffer with 200 mM NaCl. This peak was then loaded onto chromatography column containing trypsin-sepharose for purification of the inhibitor (EcTI). After purification, EcEB and ECTI were evaluated for their effects on proteases and intestinal bacteria of Aedes aegypti, and its development. EcEB and ECTI showed inhibitory activity against the instestinal homogenate of the larvae. SDS - PAGE showed the purification process was effective. The mean lethal concentration to kill 50% of subjects (LC50) was determined for EcEB (519.56 μg/mL) and the ECTI (> 1.000 μg/ml). In addition, the EcTI proved to slow the development of Ae. aegypti in a situation of chronic ingestion and to be bacteriostatic against intestinal bacteria of mosquito larvae L4.The results of the effect of EcTI on larvae and midgut bacteria of Ae. aegypti suggest that this molecule has great potential for development of new insecticides.