Prospecção fitoquímica do extrato aquoso das partes aéreas de cnidoscolus phyllacanthus (Müll. Arg.) Pax & K. Hoffm e avaliação larvicida do aedes aegypti L. (Diptera: Culicidae) no Estádio L3

Abstract

The caatinga biome covers a large part of the national territory and has a rich variety of species. It is one of the least studied Brazilian biomes, although it is the main ecosystem of the Northeast region, besides being restricted to the national territory and owning endemic plants that are important sources of natural resources. Much recent research has focused on controlling and combating Aedes aegypti, and bringing the challenge of combating mosquito vectors of diseases such as dengue fever and other arboviruses such as Chikungunya fever and Zika fever effectively. Considering the low exploitation of Caatinga plant species and the need for new products with insecticidal potential, the present work aimed to perform the phytochemical prospection of the aqueous extract of the species Cnidoscolus phyllacanthus, popularly known as "faveleira", and to determine the larvicidal activity of extracts of the leaves of C. phyllacanthus on larvae of the A. aegypti stage L3. The concepts used cover topics on the caatinga biome, family, genus and species studied, considerations on the chemistry of natural products, secondary metabolites and on the insect A. aegypti. The leaves of the species and A. aegypti eggs were collected in the city of Serra Talhada/PE. The leaves were submitted to drying in an oven for 48 h at 50 ºC, after being dried powder. The aqueous extract was prepared from the suspension of 25 g of leaf powder in 250 mL of distilled water for phytochemical prospecting, and on a three-fold scale for the larvicidal tests, shaken for 1 h, then vacuum filtered. The larvicidal activity test was performed in five replicates with dilutions of 30%, 22.5%, 15%, 7.5% and 1%, compared to larvicidal pyriproxyfen (positive control) at a concentration of 2 mg L-1 and distilled water (negative control). The larvicidal activity was evaluated every 12 h, in a period of 72 h. Phytochemical prospecting of the aqueous extracts of C. phyllacanthus leaves detected the presence of some classes of secondary metabolites: phenolic compounds, triterpenes, suspected steroids, alkaloids for Dragendorff and Bouchadart reactive and saponins. From the obtained results it is concluded that the aqueous extract extracted from the leaves of C. phyllacanthus at the concentration used has larvicidal potential on larvae in the third stage of A. aegypti at 30% and 22.5% dilutions and the estimated LC50 was 15.7%. Through the results obtained, other studies of the larvicidal evaluation of this species should still be performed as well as evaluation of the effects on health and the environment for the use of the aqueous extract of the species as larvicide.