title: Larvicidal activity of natural and modified triterpenoids against Aedes aegypti (Diptera: Culicidae).
abstract: BACKGROUND
  Insecticide resistance to commonly used substances demands new molecules for the chemical control of the dengue vector Aedes aegypti. Because natural product sources have been an alternative to obtain larvicidal compounds, the aim of this study was to evaluate the triterpenoids betulinic (BA) and ursolic (UA) acids and their semi-synthetic derivatives against larval Ae. aegypti. BA, UA, ten derivatives modified at the C-3 position and a positive control (diflubenzuron) were evaluated. Larvicidal assays were carried out with early fourth-instar larvae, and mortality was observed between 48 and 96 h. Doses from 200 to 10 ppm were used to calculate lethal concentrations (LCs).
  
  
  RESULTS
  Natural compounds, i.e. UA and BA, had the lowest LCs (LC50 of 112 and 142 ppm respectively), except for the modified compound 2b (LC50 of 130 ppm). Larvicidal activity increased significantly from 48 to 96 h for all the compounds evaluated, ranging from 20 to 50% after 48 h and from 48 to 76% after 96 h. Some derivatives, e.g. 2a and 2d, had up to a three-fold larvicidal activity increase from 48 to 96 h.
  
  
  CONCLUSIONS
  BA, UA and their derivatives showed larvicidal activity against Ae. aegypti larvae, increasing significantly from 48 to 96 h. The presence of a hydroxyl group is essential for larvicidal potential in these triterpenoids. © 2016 Society of Chemical Industry.
authors: Phytochemistry and Organic Synthesis Laboratory, School of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors: Gloria Ns
authors: GN
authors: da Silva
authors: Insect Bioecology Laboratory, Department of Biology, Federal University of Rondônia, Porto Velho, Rondônia, Brazil.
authors: Frances Tt
authors: FT
authors: Trindade
authors: Phytochemistry and Organic Synthesis Laboratory, School of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors: Francine
authors: F
authors: Dos Santos
authors: Phytochemistry and Organic Synthesis Laboratory, School of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors: Grace
authors: G
authors: Gosmann
authors: Insect Bioecology Laboratory, Department of Biology, Federal University of Rondônia, Porto Velho, Rondônia, Brazil.
authors: Alexandre A
authors: AA
authors: E Silva
authors: Phytochemistry and Organic Synthesis Laboratory, School of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors: Simone Cb
authors: SC
authors: Gnoatto
mesh_terms: D000330:Aedes; D000818:Animals; D003715:Dengue; D004132:Diflubenzuron; D007303:Insect Vectors; D007306:Insecticides; D007814:Larva; D053978:Pentacyclic Triterpenes; D014315:Triterpenes; D000094062:Betulinic Acid; D000097245:Ursolic Acid
chemical_list: D004132:Diflubenzuron; D007306:Insecticides; D053978:Pentacyclic Triterpenes; D014315:Triterpenes; D000094062:Betulinic Acid; D000097245:Ursolic Acid
keywords: Aedes aegypti; betulinic acid; dengue; larvicidal assay; triterpenoid derivatives; ursolic acid