Bioatividade dos extratos de Annona glabra L. (Magnoliales: Annonaceae) sobre a fase larval de Aedes aegypti (Diptera: Culicidae)

Abstract

The species Aedes aegypti (Diptera: Culicidae) is responsible for the transmission of several arboviruses (dengue, chikungunya, yellow fever and zika), due to its competence in the transmission of these pathogens and damage to human health, control is necessary. The plant Annona glabra (Magnoliales: Annonaceae) is presented in the scientific literature having a wide range of properties and among them, the insecticidal action. The objectives of this study were to evaluate the larvicidal activity, residual action and lethal concentrations (LC50 and LC90) of extracts from the plant on the larval stage (L3) of A. aegypti. The extraction process took place from green and ripe fruits in a fractional way using hexane [CH3(CH2)4CH3], dichloromethane (CH2Cl2) and ethanol (CH3CH2OH) as solvents. The percentages of mortality with the highest values recorded were for both extracts of the fruits (green and ripe) extracted with CH2Cl2, but the highlight was on account of the green fruit that recorded an increasing linear pattern as the analyzed concentrations increased, demonstrating a concentration relationship/(larvicidal) effect on A. aegypti. The two highest concentrations 160 and 320 ppm in the period of 24 h killed 60 and 72%, respectively, of the tested larvae and when the observations of these same groups were carried out in the period of 48 h, a total mortality of 86% was recorded for 160 ppm and for 320 ppm registered 96%. The residual action with extract of unripe fruits (CH2Cl2) at the highest concentrations showed significant mortality rates and over time this rate was reduced. This occurred at all concentrations from the beginning to the end of the experiment, but the only exception was at 320 ppm, where there was a certain constancy in the mortality rate that came to reduce over the days. The effect of ethanol extracts (CH3CH2OH) from unripe and ripe fruits in the experimental models showed a reduced ability to control larvae, and it is plausible to say that the polarity of substances with greater larvicidal effect were better extracted with dichloromethane and not with ethanol. The dichloromethane extract of unripe fruits showed the lowest values of lethal concentration, being the LC50 equal to 160.61 ppm and 10.13 ppm at 24 and 48 h respectively and the LC90 equal to 445.39 ppm and 216.52 ppm for 24 h and 48 h respectively, so the greatest effectiveness was achieved after 48 h of extract application. The results found in this study for the extracts of the fruits of the species A. glabra indicate that the plant has larvicidal activity and promising applicability.