Potencial larvicida do extrato hidroalcoólico das raízes de Tagetes patula sobre Aedes aegypti

Abstract

Aedes aegypti is one of the main vectors of arboviruses in Brazil, and its control faces challenges due to resistance to synthetic insecticides and the environmental impacts of these products. This study evaluated the larvicidal activity of hydroalcoholic extracts from fresh and dried roots of Tagetes patula against fourth-instar larvae of A. aegypti. The objective was to assess the larvicidal potential of root extracts on A. aegypti. The experiment was carried out through the cultivation, collection, and preparation of roots, followed by maceration in a hydroalcoholic solution. Three concentrations (10, 50, and 100 mg/mL) were tested in bioassays with larval groups, using positive (Bacillus thuringiensis israelensis) and negative (distilled water) controls. Larvae were exposed for 48 hours and evaluated at predefined intervals, considering as dead those that met the criteria established by the World Health Organization (WHO). Data were analyzed using a Generalized Linear Mixed Model (GLMM), with CL₅₀ and CL₉₀ estimates. The results showed that larval mortality depended on both time and extract concentration. At 100 mg/mL, the fresh root extract reached 100% mortality in less than 10 hours, while the dried root extract required up to 24 hours. At intermediate concentrations (50 mg/mL), the fresh root extract performed better (96,7%) compared to the dried root extract (80,5%). At lower concentrations (10 mg/mL), both extracts showed low effectiveness, with significant variation among replicates. CL₅₀ analysis indicated greater potency of the fresh root extract (≈ 9–10 mg/mL at 24–48h), in contrast to higher values for the dried roots (≈ 37–85 mg/mL).It is concluded that T. patula roots contain compounds with larvicidal activity, but further studies are needed to identify the compounds responsible for these effects, as well as to determine whether toxic effects are also observed in non-target organisms.