Caracterização química e avaliação das atividades antimicrobianas da cutícula do inseto adulto de Rhynchophorus palmarum

Abstract

The main function of cuticular lipids in insects is to limit water loss through the surface. However they are also involved in various types of chemical communication between species and reduced penetration insecticides chemicals, and toxins as well as provide protection against the attack of microorganisms, parasites and predators. Numerous species of insect vectors of highly virulent diseases of plants, play a critical role as agricultural pests as in the case of Rhynchophorus palmarum which is vector in nematode transmitter red ring disease is responsible for causing damage to the agricultural economy of palm trees, in particular coconut in various regions of the country. However, the susceptibility or resistance of various insect species, infection can result from several factors, including differences in structure and composition of the exoskeleton, and the presence of antimicrobial compounds in the cuticle. The role of the host surface lipids in the pathogenesis of insects is still poorly understood. The determination of cuticular lipids profile is therefore of great importance to understanding insect susceptibility or resistance to infection. This study aimed to characterize the cuticular profile adult insect R. Palmarum male and female, and evaluate the presence of antimicrobial activity. The analyzes were performed by gas chromatography-mass spectrometry of the hexane fractions (extract I) and dichloromethane (extract II and III). the main cuticular components were identified as hydrocarbons, alcohols, ketone and aldehyde, both in male and in female, including the presence of alkanes (C25; C27; C43) trimethyl-alkane (C40) identified in the extract II female insect unsaturated hydrocarbons (C20:5) in the extract I female and male, and methyl branched alkene (C24:6) only in female extract II. They identified 10 fatty acid esters of C14 to C23, with variation between the sexes in C22:0, C18:1, C21:0 and C20:2. Showed relevant amounts of C16 and C18, the common cuticular lipids extract (II) and internal (III). The extracted chitin cuticle, chitosan and derivative thereof, in the study were characterized by IR and X-ray diffraction. The extracts of cuticle were satisfactory inhibition against Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Candida albicans and Candida tropicalis.