Estudo fitoquímico e abordagem sobre a atividade larvicida de Helicteres Eichleri K. Schum (Sterculiaceae) frente a Aedes aegypti L. (Diptera: Culicidae)

Abstract

Since the dawn of human existence, populations around the world have been using natural products for medicinal purposes and spreading this knowledge for generations. In contemporary times, with the advances of science, the interest of researchers who seek in the medicinal plants the discovery of new bioactive substances has been intensified. In the world scenario, Brazil stands out as one of the countries with the greatest prospects for the sustainable exploitation of its biodiversity, since it holds the greatest diversity of plant species in the world. In this context, we emphasize the importance of research on plant species that present themselves as natural sources to combat the various stages of the Aedes aegypti mosquito, the main vector responsible for the transmission of dengue, zika, chikungunya and yellow fever viruses. This search for natural insecticides from renewable resources that are rapidly degradable, less damaging to the environment and human health, and the study of the use of Helicteres velutina in indigenous medicine against insect bites have led us to isolate and identify the chemical constituents, as well as to evaluate the larvicidal potential against Aedes aegypti of the species Helicteres eichleri K. Schum (Sterculiaceae), popularly known in Brazil as "monkey smoke".Through a chemical and biological pioneer study of the crude ethanolic extract obtained from the aerial parts of this species and using chromatographic and spectroscopic techniques, substances were isolated and identified, respectively: decanol (He-1), rosmarinic acid (He -2), a mixture of βsitosterol and stigmasterol (He-3a and He-3b), lupeol (He-4), a mixture of 3-α-hydroxy-urs-12en-28-oic and 3-α-hydroxy-olean-12-en-28-oic (He-5a and He-5b), a mixture of micromeric acid and ursolic acid (He-6a and He-6b). A preliminary approach, based on the exposure of the larvae in the L4 stage of Aedes aegypti to different concentrations of the crude ethanolic extract from the aerial parts of Helicteres eichleri, demonstrated promising larvicidal activity. After 24 and 48 hours of exposure, the concentration of 20mg/mL was able to kill 92.5% and 93.3% of the larvae, respectively. The LC50 was calculated at 4.4 mg/mL for the 24-hour interval, and, using the Tukey's test model, after 48 hours of exposure, LC50 was 3.73 mg/mL, thus characterizing a favorable alternative to be used in an integrated control system of this vector.