Cytotoxicity of Piper aduncum (Piperaceae) essential oil in brown stink bug Euschistus heros (Heteroptera: Pentatomidae).

Euschistus heros (F.) (Hemiptera: Pentatomidae) is a soybean pest in Brazil, controlled with synthetic chemical insecticides, which may be harmful to the environment and humans, as well as to select pest resistant strains. The research for new pest control strategies such as the use of plant essential oils has been increased due to the selectivity and biodegradation of these molecules. The objective was to evaluate the cytological changes in the salivary glands, fat body and midgut of E. heros exposed to different concentrations of essential oil of Piper aduncum L. (Piperales: Piperaceae), which the main compounds were identified as myristicin 30.03%, aromadendrene 9.20%, dillapiole 8.43%, α-serinene 7.31%, tridecane 6.26%, γ-elemene 4.58% and o-cymene 4.20%. The essential oil of P. aduncum was toxic for E. heros with LD50 = 36.23 mg per insect and LD90 = 50.42 mg per insect. Cytological changes such as tissue disruption, increase in mitochondria population, and glycogen and lipid depletion occur in the fat body cells, whereas salivary glands and midgut are not affected by this essential oil. Results suggest that P. aduncum essential oil causes fat body cellular stress, which may compromise some physiological processes for the insect survival.

Larvicidal and cytotoxic potential of squamocin on the midgut of Aedes aegypti (Diptera: Culicidae).

Acetogenins are secondary metabolites exclusively produced by Annonaceae, which have antitumor, cytotoxic, and pesticide activities. In this study, we evaluated the larvicidal and cytotoxic effect of squamocin from Annona squamosa on Aedes aegypti (Diptera: Culicidae) midgut. The compound was solubilized in 2% Tween 20 at 10, 20, 50, 80 and 100 ppm. The assay was conducted in a completely randomized design with four replications, each with 20 third-instar larvae. Larval mortality was assessed every hour until total mortality, and the data were subjected to Probit analysis. Cellular damage was evaluated every 30 min in groups comprising five larvae subjected to squamocin at 50 and 100 ppm for 240 min. The total larval mortality occurred after 360 min following application of 50, 80, and 100 ppm squamocin, and 600 min after applying other concentrations with LC50 at 6.4 ppm. Both 50 and 100 ppm of squamocin showed cytotoxic activity in the midgut epithelium of A. aegypti after 240 min with 50 ppm resulting in midgut cells with light cytoplasm containing small vacuoles, whereas at 100 ppm were found cells with cytoplasm highly vacuolated, damaged apical surface and cell protrusion toward the gut lumen. In conclusion, squamocin has the potential to control A. aegypti.