Insecticidal activity of Leptodactylus knudseni andPhyllomedusa vaillantii crude skin secretions against the mosquitoes Anopheles darlingi andAedes aegypti

Background Mosquitoes are important vectors of several diseases, including malaria and dengue, and control measures are mostly performed using chemical insecticides. Unfortunately, mosquito resistance to commonly applied insecticides is widespread. Therefore, a prospection for new molecules with insecticidal activity based on Amazon biodiversity using the anuransLeptodactylus knudseni andPhyllomedusa vaillantii was performed against the mosquito speciesAnopheles darlingi and Aedes aegypti.Methods The granular secretion from anuran skin was obtained by manual stimulation, and lethal concentrations (LCs) for larvicidal and adulticidal tests were calculated using concentrations from 1-100 ppm. The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species.Results The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species. The calculated LC50 of L. knudseni skin secretions against An. darlingiwas 0.15 and 0.2 ppm for adults and larvae, respectively, but much higher for Ae. aegypti, i.e., 19 and 38 ppm, respectively. Interestingly, the calculated LCs50 of P. vaillantii against both mosquito species in adults were similar, 1.8 and 2.1 ppm, respectively, but the LC50 forAn. darlingi larvae was much lower (0.4 ppm) than forAe aegypti (2.1 ppm).Conclusions The present experiments indicate that skin secretions from L. knudseni and P. vaillantii contain bioactive molecules with potent insecticide activity. The isolation and characterization of skin secretions components will provide new insights for potential insecticidal molecules.(AU)

Insecticidal activity of Leptodactylus knudseni and Phyllomedusa vaillantii crude skin secretions against the mosquitoes Anopheles darlingi and Aedes aegypti

Mosquitoes are important vectors of several diseases, including malaria and dengue, and control measures are mostly performed using chemical insecticides. Unfortunately, mosquito resistance to commonly applied insecticides is widespread. Therefore, a prospection for new molecules with insecticidal activity based on Amazon biodiversity using the anurans Leptodactylus knudseni and Phyllomedusa vaillantii was performed against the mosquito species Anopheles darlingi and Aedes aegypti. The granular secretion from anuran skin was obtained by manual stimulation, and lethal concentrations(LCs) for larvicidal and adulticidal tests were calculated using concentrations from 1-100 ppm. The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species. The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species. The calculated LC50 of L. knudseni skin secretions against An. darlingi was 0.15 and 0.2 ppm for adults and larvae, respectively, but much higher for Ae. aegypti, i.e., 19 and 38 ppm, respectively. Interestingly, the calculated LCs50 of P. vaillantii against both mosquito species in adults were similar, 1.8 and 2.1 ppm, respectively, but the LC50 for An. darlingi larvae was much lower (0.4 ppm) than for Ae aegypti (2.1 ppm). The present experiments indicate that skin secretions from L. knudseni and P. vaillantii contain bioactive molecules with potent insecticide activity. The isolation and characterization of skin secretions components will provide new insights for potential insecticidal molecules.

Evaluation of larvicidal activity of the methanolic extracts of Piper alatabaccum branches and P. tuberculatum leaves and compounds isolated against Anopheles darlingi

Piper is a notable genus among Piperaceae due to their secondary metabolites such as lignans, amides, esters and long chain fatty acids used as anti-herbivore defenses with comparable effects of pyrethroids, that holds a promise in insect control, including malaria vectors such as Anopheles darlingi, the main vector in the North of Brazil. Methanolic extracts of Piper tuberculatum Jacq., Piperaceae, and P. alatabaccum Trel. & Yunck., Piperaceae, and some isolated compounds, i.e, 3,4,5-trimetoxy-dihydrocinamic acid, dihydropiplartine; piplartine, piplartine-dihydropiplartine and 5,5',7-trimetoxy-3',4'-metilenodioxiflavone were tested as larvicides against A. darlingi. The Lethal Concentrations (LC50 and LC90) of methanolic extracts were 194 and 333 ppm for P. tuberculatum and 235 and 401 ppm for P. alatabacum, respectively. Isolated compounds had lower LC values, e.g. the LC50 and LC90 of the piplartine-dihidropiplartine isolated from both plant species was 40 and 79 ppm, respectively.