ÓLEOS ESSENCIAIS DE PIPER TUBERCULATUM E PIPER BRACHYPETIOLATUM (PIPERACEAE) NO CONTROLE DE AEDES AEGYPTI LINNAEUS, 1762 (DIPTERA: CULICIDAE) EM CONDIÇÕES DE LABORATÓRIO

Abstract

Dengue is one of the most concerning arboviral diseases in the world, affecting millions of people annually. In 2024, the Pan American Health Organization (PAHO) reported over 10,239,883 probable cases in Brazil. The rise in temperatures and rainfall across the country, associated with the El Niño phenomenon, has favored the proliferation of Aedes aegypti, the main arbovirus vector in Brazil. This mosquito exhibits a high capacity for adaptation to urban environments and has developed resistance to synthetic chemical insecticides, such as pyrethroids, organophosphates, and carbamates. This resistance is associated with genetic mutations and biochemical defense mechanisms, particularly those mediated by enzymes such as acetylcholinesterase (AChE), which reduce the effectiveness of these compounds. Furthermore, the continuous use of these insecticides at increasingly higher concentrations has caused environmental impacts, especially affecting non-target aquatic organisms. On the other hand, essential oils (EOs) have emerged as a natural chemical control alternative against the vector. In this study, we investigated the larvicidal activity and mechanisms of action of EOs extracted from Piper tuberculatum and Piper brachypetiolatum, as well as their main constituents, β-caryophyllene and (E)-nerolidol, against A. aegypti and non-target aquatic organisms. EO extraction from the leaves of these plants yielded 0.45 ± 0.7% for P. tuberculatum and 1.5 ± 0.7% for P. brachypetiolatum, with β-caryophyllene (54.8%) and (E)-nerolidol (64.32%) identified as the major constituents, respectively. The EOs and their major compounds demonstrated significant larvicidal activity, with LC₅₀ values of 15.51 μg/mL for P. brachypetiolatum, 48.61 μg/mL for P. tuberculatum, 57.20 μg/mL for β-caryophyllene, and 9.50 μg/mL for (E)-nerolidol. Exposure of larvae to these substances resulted in oxidative stress, as evidenced by the increased production of reactive oxygen and nitrogen species (RONS). P. tuberculatum and β-caryophyllene, tested at 100 μg/mL, induced oxidative stress levels of 405.6 ± 11% and 330.7 ± 6%, respectively. P. brachypetiolatum and (E)-nerolidol, evaluated at 30 mg/L, exhibited stress values of 449.7 ± 18% and 365.7 ± 11%, respectively, which were directly associated with elevated ROS production. The EOs and their constituents inhibited acetylcholinesterase (AChE) activity, impairing neuromuscular transmission and resulting in larval paralysis and death. The IC₅₀ values were 57.78 μg/mL for P. tuberculatum, 71.97 μg/mL for β-caryophyllene, 44.97 mg/L for P. brachypetiolatum, and 11.07 mg/L for (E)-nerolidol. Ecotoxicity tests showed that the EOs and their compounds were non-toxic to non-target aquatic species such as Diplonychus indicus, Toxorhynchites haemorrhoidalis, and Anisops bouvieri, ensuring 100% survival of these organisms. In contrast, the synthetic insecticide α-cypermethrin caused 100% mortality in these species, highlighting the environmental harm of conventional insecticides. Therefore, the results suggest that the EOs of P. tuberculatum and P. brachypetiolatum, along with their major constituents, are promising larvicidal agents for controlling A. aegypti, combining high efficacy with low environmental toxicity.