[Ultrastructural alterations in larvae of Aedes aegypti subject to labdane diterpene isolated from Copaifera reticulata (Leguminosae) and a fraction enriched with tannins of Magonia pubescens (Sapindaceae)]. / Alterações ultraestruturais em larvas de Aedes aegypti submetidas ao diterpeno labdano, isolado de Copaifera reticulata (Leguminosae), e à uma fração rica em taninos de Magonia pubescens (Sapindaceae).

INTRODUCTION: Dengue is an important public health problem in many countries and its main vector Aedes aegypti, is the mosquito most adapted to urban areas. For the first time, the mechanism of action of labdane diterpenoid extracted from Copaifera reticulata and the fraction enriched of catechin tannins extracted from Magonia pubescens is demonstrated through ultrastructural alterations of Aedes aegypti larvae. METHODS: Experiments were performed using a 0.9 ppm solution of diterpenoid and 3.7 ppm of the fraction as the main catechin tannin of molecular mass 846 Da. The compounds were obtained by thin layer chromatography and identified by nuclear magnetic resonance of hydrogen and mass spectrometry. Larvae that achieved lethargic state were collected and dissected. Next, they were contrasted with 1% uranyl acetate, dehydrated, embedded and polymerized. Ultrathin sections were made, mixed with 3% uranyl acetate and lead citrate and placed in an electron microscope. RESULTS: The main ultrastructural alterations caused by the diterpenoid and by tanins in larvae of Aedes aegypti were: cytoplasmic vacuolation, alteration of microvilli, cellular aging, cell disruption and degeneration, formation of secretion vesicles and structural changes in microvilli, irregular nuclei and displacement of cells in the basal lamina. CONCLUSIONS: The fraction containing tannins and the diterpenoid caused the death of Aedes aegypti larvae by cell destruction in the midgut.

Larvicidal activity of oil-resin fractions from the Brazilian medicinal plant Copaifera reticulata Ducke (Leguminosae-Caesalpinoideae) against Aedes aegypti (Diptera, Culicidae).

Oil-resin fractions from Copaifera reticulata Ducke (Leguminosae-Caesalpinoideae) were evaluated for larvicidal activity on third larval instars of Aedes aegypti, in searching for alternative control methods for this mosquito. The bioactive fractions were chemically monitored by thin-layer chromatography, (1)H and 13C nuclear magnetic resonance and mass spectrometry. Bioassays were performed using five repetitions, at a temperature of 28+/-1 degrees C, relative humidity of 80+/- 5% and light and dark cycles of 12h. Mortality was indicated by darkening of the cephalic capsule after 24h of exposure of the larvae to the solutions. The most active fractions were CRM1-4 (sesquiterpenes) and CRM5-7 (labdane diterpenes), which showed LC50 values of 0.2 and 0.8 ppm, respectively.

[Toxicity of the ethanol extract of Magonia pubescens on larvae Aedes aegypti]. / Toxicidade do extrato etanólico de Magonia pubescens sobre larvas de Aedes aegypti.

Crude ethanol extracted from Magonia pubescens trunks was utilized to prove its effect in the intestinal tract of Aedes aegypti 3rd instar larvae. Exposure times (2, 4, 6, 8, 10, 12, and 13 hours) were tested to verify when the morphological alterations begin to occur, in the intestinal tract of the larvae. The toxic effect of the extract was mainly in the midgut, beginning at the anterior midgut and followed through to posterior midgut. The main alterations observed were partial or total cell destruction, high citoplasmatic vacuolization, increase of subperitrophic space, cell hypertrophy and the epithelium did not maintain its monolayer appearance. The alterations began after four hours of exposure to M. pubescens extract. Observations of tissue sections from larvae treated for different lengths of time revealed a wide variation in the degree of damage between exposure periods and midgut larvae region. The present study provides evidence regarding the mode of action of the M. pubescens extract and suggests its potential utilization as a larvicide to control Aedes aegypti mosquito.