Heloísa Helena Garcia da Silva

Atividade larvicida de taninos isolados de Magonia pubescens St. Hil. (Sapindaceae) sobre Aedes aegypti (Diptera, Culicidae)

Phytochemical study of the larvicidal fractions which were carried out for the first time, isolated of the Magonia pubescens, monitored by the study of efficacy against the 3rd larval instar of Aedes aegypti, in the search of alternatives for the control of that mosquito and to obtain structures susceptible to chemical improving of the activity for the synthetic via of other derived. The fractions with biological activity were monitored chemically through chromatography of thin layer, using as revealing a solution acid of vanillin, analyzed by nuclear magnetic resonance of hydrogen and spectrometry of masses. The bioassays with the fractions were accomplished with five replications, controlled at the temperature of 28+/-1 degrees C, 80+/-5% of relative humidity and 12 h light. The found lethal concentrations of the fraction that it presented the largest potential larvicidal, MP-9, LC50 and LC90, were of 3.1 and 36.6 ppm, respectively. All the experiments were accompanied by a control series, containing the same number of larvae.

Ovicidal Activity of Entomopathogenic Hyphomycetes on Aedes aegypti (Diptera: Culicidae) Under Laboratory Conditions

Abstract The ovicidal activity of 21 hyphomycete fungi species against Aedes aegypti (L.) (Diptera: Culicidae) was tested. Fungi with ovicidal activity developed on high numbers of eggs (≥70%) during 25 d of exposure. A clear ovicidal activity with low values of hatch (1.3–40%) was observed after 25 d of incubation with Isaria farinosa (Holm: Fries) Fries, Paecilomyces carneus (Duché & Heim) Brown & Smith, Paecilomyces marquandii (Massee) Hughes, Isaria fumosorosea (Wize), Metarhizium anisopliae (Metschnikoff) Sorokin, Penicillium sp., Paecilomyces lilacinus (Thom) Samson, Beauveria bassiana (Balsamo) Vuillemin, and Evlachovaea kintrischica Borisov & Tarasov. More than 63% of eggs hatched after 25-d exposures to 11 other fungi species deemed as ineffective. These are the first results to show the effects of entomopathogenic fungi against eggs of Ae. aegypti, and they suggest their potential as control agents of this vector.

Impact of moisture on survival of Aedes aegypti eggs and ovicidal activity of Metarhizium anisopliae under laboratory conditions

The effect of relative humidity (43%, 75%, 86% and > 98%) on Aedes aegypti eggs treated with Metarhizium anisopliae or water only was tested for up to a six months exposure at 25 degrees C. Survival of larvae inside eggs was clearly affected by the lowest humidity (43%) tested, and eclosion diminished at all humidities after increasing periods of exposure. M. anisopliae showed to have a strong ovicidal activity only at humidity close to saturation. No difference of activity was found between conidia and hyphal bodies tested. This fungus affected larvae inside eggs and has potential as a control agent of this important vector in breeding sites with high moisture.

Influência do período de quiescência dos ovos sobre o ciclo de vida de Aedes aegypti (Linnaeus, 1762) (Diptera, Culicidae) em condições de laboratório

The influence of the period of egg quiescence on the life cycle of Aedes aegypti (Linnaeus, 1762) (Diptera, Culicidae) was studied under laboratory conditions in order to improve the management of vector control. The eggs are known to be the most resistant stages during development, allowing a long survival of the mosquitoes under unfavorable climatic conditions. The experiments were performed in a biological chamber kept at 28 ± 1oC temperature, with 80 ± 5% relative humidity and 12 hours of photophase. Data about the influence of different periods of quiescence on eclosion, larval and pupal development and the developmentals cycle are presented. We observed a highly significant effect of the period of quiescence on larval eclosion. The period of quiescence had no influence on the duration of larval or pupal incubation. Eggs originating from the same period of quiescence showed significantly different periods of incubation The larvae emerged in groups defined by the period of incubation. This group effect was significant during the cycle. In 99.8% of the cycles the variation was determined by incubation.

Larvicidal activity of Copaifera reticulata ducke oil-resin against Culex quinquefasciatus Say (Diptera: Culicidae)

The appearance of resistance of Culex quinquefasciatus Say to chemical insecticides and the modification of the susceptibility of this mosquito to pyrethroid has stimulated studies on the activity of plants as alternative for its control. In this study, bioassays were carried out to verify the larvicidal activity of the oil-resin of Copaifera reticulata on C. quinquefasciatus. The bioassays were carried out with the oil dissolved in dimethylsulfoxide (DMSO), at the proportion of 0.4 ml of DMSO to 24.6 ml of distilled water. For each instar, the bioassays were carried out in plastic glasses with 100 ml solution using 20 larvae, wit four replications to adjust the lethal concentrations. The mortality observations were made after 48h exposure of the larvae to the solution. The control was carried out in distilled water and DMSO, with the same number of replications as the bioassays. The experiments were carried out in a biological chamber, controlled at 28 ± 1°C, 80 ± 5% relative humidity and 12h light. The larvae without movement were considered dead. The C. reticulata oil-resin demonstrated larvicide activity for all the C. quinquefasciatus instars. The LC50 found for the 1st, 2nd, 3rd and 4th larval instars were: 0.4, 0.9, 39 and 80 ppm, and the LC99 were 15, 15, 50 and 180 ppm, respectively.

Associação entre incidência de dengue, pluviosidade e densidade larvária de Aedes aegypti, no Estado de Goiás

INTRODUCTION: The larval density of Aedes aegypti fluctuates according to seasonal climatic changes. It rises in seasons with higher rainfall, according to the number of potential breeding sites available, thereby predisposing towards increased incidence of dengue. This study aimed to show the association between dengue cases, rainfall and the building infestation rate. METHODS: The municipalities were stratified according to the risk and transmission of dengue, and according to presence or absence of mosquito infestation. We used the building larval infestation rate as an indicator for the risk of transmission. RESULTS: There was a positive correlation between the building infestation rate, number of dengue cases and rainfall. Disease transmission was greater during the first four months of each year studied (period of high rainfall) and lower between June and September (season with low rainfall). Dengue cases occurred continually and in increased numbers between January and March of each year, and then declined in the months of April and May, when it ceased in most municipalities. The metropolitan region of Goiânia was responsible for more than 80% of the dengue cases in Goias. Transmission was continuous throughout the year, although lower during the period from May to December. Over the last three months, there was increased transmission, but usually still at low rates. CONCLUSIONS: The positive correlation between the building infestation rate and rainfall, and between this rate and the incidence of cases, indicated a significant association between increasing transmission and increasing numbers of dengue cases.

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.

Larvicidal effects of fungal Meroterpenoids in the control of Aedes aegypti L., the main vector of dengue and Yellow fever.

The mosquito Aedes aegypti is an increasing problem of public health, being the vector responsible for dengue and Yellow Fever in tropical and subtropical regions. The aim of this work was to determine the potential larvicidal activity of a series of meroterpenoids, compounds 1–7, previously obtained fungal secondary metabolites from Penicillium sp., against the third‐instar larvae of A. aegypti. The lethal concentrations (LC50 and LC90) of 1–7 were evaluated 24 h after exposure. Dehydroaustin (4) was the most active meroterpenoid in the series, with an LC50 value of 2.9 ppm, making it an attractive natural insecticide.

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 0.9ppm solution of diterpenoid and 3.7ppm of the fraction as the main catechin tannin of molecular mass 846Da. 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.

Diterpenos de Copaifera reticulata Ducke com atividade larvicida contra Aedes aegypti (L.) (Diptera, Culicidae)

The objective of this study was to evaluate the larvicidal activity of diterpenoids obtained from the oil-resin of Copaifera reticulata against Aedes aegypti larvae, the principal vector of dengue and urban yellow fever. Four diterpenes were obtained from oil-resin extraction with organic solvents and subsequent chromatographic and spectroscopic procedures allowed to isolation and identification of these compounds as 3-beta-acetoxylabdan-8(17)-13-dien-15-oic acid (1), alepterolic acid (2), 3-beta-hidroxylabdan-8(17)-en-15-oic acid (3), and ent-agatic acid (4). Each compound was previously dissolved in dimethylsulphoxide, and distilled water was added to obtain the desired concentrations. Twenty larvae of third instars were placed into plastic beckers, containing the solution test (25 mL), in a five repetitions scheme, and their mortality, indicated by torpor and darkening of the cephalic capsule, was recorded after 48 h. Probit analyses were used to determine lethal concentrations (LC50 and LC90) and their respective 95% confidence intervals. This study showed that only diterpenoids 1 and 2 exhibited larvicidal properties with LC50 of 0.8 ppm and 87.3 ppm, respectively, revealing the former as the most toxic compound against third instars of Ae. aegypti. Therefore, this compound seems to be an interesting source for new metabolite to be exploited.