Efeito toxicogenético de dois derivados do dilapiol in vitro e ensaios simulados de campo em Aedes (Stegomyia) aegypti (Diptera:Culicidae), da Amazônia Central

Abstract

The resistance of Aedes (Stegomyia) aegypti, the primary vector of the viruses that cause dengue, Zika and chikungunya, to synthetic chemical insecticides has required the search for alternatives for its vector control. Dillapiole, present in Piper aduncum and its derivatives, are effective alternatives for the control of this mosquito. The toxic and genotoxic effects of the new dillapiole derivatives, propyl ether dillapiole and piperidyl dillapiole were evaluated for the first time in Ae. aegypti in the laboratory and under simulated field conditions, in vitro in Artemia salina and in cell culture. A total of 1,690 samples, including 780 eggs, 780 larvae and 130 adults, were treated with different concentrations of the substances for 4 h, 24 h and 90 min, respectively. The larvicide temephos (0.012 µg/mL) was used as a positive control, dillapiole (80 µg/mL) as a comparative and water + DMSO 0.05% as a negative control. Changes in larval external morphology were analyzed. Under simulated field conditions, the larvicidal and residual effect of the derivatives were evaluated, at the same concentrations evaluated in the laboratory. Larvae (n = 6,000) exposed to 10 µg/mL of the substances and temephos (0.001 µg/mL) had their enzymatic activity (catalase - CAT, glutathione S-transferase - GST, acetylcholinesterase - AChE and total proteins) analyzed. During four generations (G1 to G4), larvae were treated for 4h with sublethal concentrations of the derivatives (20 to 90 µg/mL) to prepare cytological slides (n = 720) of larval neuroblasts and oocytes of adult females. The average oviposition and egg hatching rates of these females from generations G1 to G4 were calculated. The in vitro cytotoxic effect was analyzed in Ar. salina. In L929 cells, the substances' cytotoxic, genotoxic and mutagenic action (5 to 20 µg/mL) was analyzed. Dillapiole was used to compare the two derivatives as a control and the larvicide temephos as a positive control. Negative control in water and DMSO. The 50% Lethal Concentration (LC50) of propyl ether dillapiole, piperidyl dillapiole in Ar. salina were 48.6 and 48.2 µg/mL. In L929 cells, the 50% cytotoxic concentration (CC50) of the substances were 11.02, 13.94 and 30.98 μg/mL in temephos. In Ae. aegypti, propyl ether dillapiole and piperidyl dillapiole were toxic to eggs (LC50 18.07 and 49.97 µg/mL), larvae (LC50 29.15 and 72.93 µg/mL) and adults (LC50 148.25 and 263.26 µg/mL). Under simulated field conditions, it caused larval mortality (LC50 24.60 and 31.58 µg/mL) and moderate residual effect. Sublethal concentrations of propyl ether dillapiole, piperidyl dillapiole, dillapiole and temephos inhibited AChE activity. Genotoxic and mutagenic effects on neuroblast cells of larvae and oocytes of females were significantly higher (p < 0.05) in treated individuals compared to the negative control. Cumulative damage including lower concentrations, with higher occurrence in G4, led to reduced oviposition and egg viability of treated females, especially in dillapiole propyl ether. Propyl ether dillapiole and piperidyl dillapiole are potential alternatives for effective control of Ae. aegypti. Complementary analyses are necessary to verify the efficacy and safety of these compounds in non-target organisms.