Use of essential oils from plants of Araripe National Forest against Aedes aegypti (Diptera: Culicidae).

Aedes aegypti control is achieved with chemical insecticides that can promote insecticide resistance. In the search for new forms of control, the use of botanical products is currently growing and many tests with oils have already been performed. The plant diversity of Araripe National Forest enables the study of several species against this vector. To evaluate the larvicidal effect of essential oils from plants of this forest, we used field rosemary, copaiba, bay leaf, cashew and pequi. The work was divided into three stages: all oils with the same dosage; the best oil at dosages of 0, 5, 10, 20, 50 and 75 µg/mL; and the best dosage at temperatures of 15, 20, 25, 30 and 35 °C. The oils of field rosemary, copaiba, bay leaf, cashew and pequi were good insecticides when used at dosages above 5 µg/mL. The bay leaf oil showed high larvicidal activity at all dosages tested, showing the highest efficiency at 75 µg/mL. Temperatures of 15 and 35 °C increased the susceptibility of the insect to the effect of the bay leaf oil. The essential oils of field rosemary, copaiba, bay leaf, cashew and pequi, from Araripe National Forest, applied at a dosage of 5µg/mL, showed insecticidal action, although with low efficiency.

Phytochemical prospection, hemagglutinating and insecticidal activity of saline extracts from the seeds of Tamboril (Enterolobium contortisiliquum) Vell. Morong (Fabaceae) on Aedes aegypti (Diptera: Culicidae).

This study evaluated the insecticidal activity of crude extracts from Enterolobium contortisiliquum (Vell.) seeds on eggs and larvae of A. aegypti, and also verified the phytochemical profile and the presence of lectins in the extract. The 0.15 M NaCl saline solution was used as the extracting substance. For tests with eggs and larvae, the crude extract was used in its raw form (RCE) and boiled at 100º C for 5 min (BCE). Concentrations of 4.68; 9.37; 18.75; 28.13; 37.13 and 46.89 mg/mL, with distilled water as a negative control. Assays were performed in triplicate. The results were subjected to analysis of variance, Tukey's test and Log-Probit analysis to determine LC50 and LC90. BCE showed better results on eggs than RCE, managing to prevent the hatching of larvae in 81.66% ± 10.40 of treated eggs, at a concentration of 46.89 mg/mL. The LC50 and LC90 were set at 35.95 and 52.67 mg/mL, respectively. In tests with larvae, concentrations of 46.89 and 37.13 mg/mL, for RCE and BCE, caused 100% mortality in 24 hours of exposure. Larval mortality at the other concentrations increased with exposure time extending to 48 h. RCE, at 48 h exposure is the most promising extract on larvae (E = 72.77%, LC90 = 10.86 mg/mL). In RCE, the presence of lectins and secondary metabolites: flavonoids, xanthones and phenols, were detected. The results demonstrate the potential of E. contortisiliquum seed extracts with ovicidal and larvicidal action on A. aegypti.

Phytochemical prospection and larvicidal bioactivity of the janaguba (Himatanthus drasticus) Mart. Plumel (Apocynaceae) latex against Aedes aegypti L. (Diptera: Culicidae).

The aim of this study was to carry out phytochemical prospecting and evaluate the larvicidal activity of Himatanthus drasticus latex extracts against Aedes aegypti. The extracts were obtained by maceration from 5 g of latex powder concentrated separately in 100 mL of methanol, ethyl acetate, and hexane solvents. The concentrations of 100, 200, 300, 400, and 500 ppm of each extract were tested in triplicate with a solution of pyriproxyfen as the positive control and distilled water and dimethylsulfoxide as the negative control. The phytochemical prospection of the methanolic extract showed the presence of phenolic compounds, such as anthocyanins, anthocyanidins, catechins, chalcones, aurones, leucoanthocyanidins, and condensed tannins. The insecticidal bioactivity was most significant for the methanolic extract. The methanolic extract lethal concentrations (LC) of 50 and 90% were 190.76 and 464.74 ppm, respectively. After 48 hours of exposure, the extracts using methanol, ethyl acetate, and hexane at their highest concentrations (500 ppm) caused larval mortality of 100, 73.33, and 66.67%, respectively. These extracts also promoted changes in the external morphology of the larvae, such as damage to the anal papillae, darkening of the body, and reduction in the number of bristles. The methanolic extract showed greater expressivity for morphological changes. The latex of H. drasticus has larvicidal activity against third-stade larvae of A. aegypti and it is more significant when obtained through maceration in methanol. The methanolic extract of H. drasticus latex contains phenolic compounds with insecticidal activity against A. aegypti larvae.