Toxicity of squamocin on Aedes aegypti larvae, its predators and human cells.

BACKGROUND: The mosquito Aedes aegypti transmits a virus that causes diverse human diseases, and control of the vector is an important strategy to avoid disease propagation. Plants in the family Annonaceae are recognised as sources of molecules with uses in the medical and agriculture fields. Molecules of secondary metabolites of Annonaceae plants exhibit insecticidal potential against insect pests and vectors, especially acetogenins, showing high toxicity at low doses, which has encouraged research into producing new insecticide molecules. Herein, we identify an acetogenin from Annona mucosa seeds (chemical analysis) and provide the results of toxicity tests against larvae of A. aegypti (target insect) and its predators Culex bigoti and Toxorhynchites theobaldi (non-target insects) and cytotoxicity to human leukocytes. RESULTS: We identified squamocin (C37 H66 O7 ), a fatty acid with a bis-tetrahydrofuran ring. In A. aegypti, this compound caused behavioural disturbance before larval death and high mortality at low concentrations (LC50 = 0.01 µg mL-1 and LC90 = 0.11 µg mL-1 ). However, in predators and human leukocytes, squamocin showed no toxicity effect, indicating the selectivity of this molecule for non-target organisms. CONCLUSION: We identified squamocin from A. mucosa seeds, which exhibited lethal action against A. aegypti and showed selectivity for non-target insects and low cytotoxicity to human cells. © 2016 Society of Chemical Industry.

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.