Regina Geris

Biodiesel de soja: reação de transesterificação para aulas práticas de química orgânica

The transesterification procedure of triacylglycerides from soybean oil (in natura and waste oil) to give biodiesel was adapted to semi-micro laboratory scale as an additional experimental technique of nucleophilic acyl substitution for undergraduate courses in Chemistry and related areas.

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.

Atividade larvicida de Anacardium occidentale como alternativa ao controle de Aedes aegypti e sua toxicidade em Rattus norvegicus

The search for substitutes for synthetic pesticides has been the subject of many scientific publications, including considering the use of oils, extracts and active constituents from plants. This demand can be justified by the insecticide potential associated with an easy degradation of its constituents, lower toxicity to humans and, consequently, a safer alternative for the environment. After collecting and heating the Anacardium occidentale (Anacardiaceae) fruits at 40°C, they were tested to confirm their larvicidal activity. Then, it was fractionated in a silica gel column. The fractionation resulted in eight fractions, which were coded as AO1 to AO8. In this paper, the cashew nut shell liquid (CNSL) and its fractions were evaluated as to their biological activity in the third instar larvae of Aedes aegypti. The acute oral toxicity in Rattus norvegicus also was evaluated. CNSL and the AO2 and AO3 fractions presented larvicidal activity. The lethal concentrations, LC50 and LC90, of CNSL were, respectively, 6.55 and 10.98 ppm. The active fractions, AO2 and AO3, presented LC50 and LC90 of 3.18 and of 7.80 ppm, and 3.57 and 10.47 ppm, respectively. The LCC and the fractions were orally administered at a dose of 2000 mg/kg. These products showed larvicidal potential against Ae. aegypti and no sign of toxicity was evident in the parameters analyzed.

Chapter 10 – Bioactive Natural Products as Potential Candidates to Control Aedes aegypti, the Vector of Dengue

This review deals with the description of bioactive secondary metabolites produced by the living organisms, including plants, fungi, bacteria (actinomycetes and cyanobacteria) and lichens which have activity against the mosquito Aedes aegypti, the vector responsible for dengue and yellow fever. The insecticidal activities of these compounds are discussed herein, and their mode of action and structure–activity relationships are presented when appropriate. Control agents (fungi, bacteria, and other organisms) are briefly commented since they can also be a rich source of bioactive compounds. It describes 319 compounds from plants, 25 from fungi, 27 from bacteria (including actinomycetes and cyanobacteria), and 7 from lichen and cites 264 references. Covering: up to February 2011.

Furfural - da biomassa ao laboratório de química orgânica

The goal of this manuscript is provide to students of Chemistry and related areas an alternative experiment in which they can obtain a compound and learn to observe and interpret properties and predict organic structure by obtaining furfural from biomass. Furfural is an organic compound, obtained through acid hydrolysis of pentosans, commonly used in the chemical and pharmaceutical industries. Students are guided to get furfural through extractive procedures and chemical reactions adapted to semi-micro laboratory scale. Characterization of furfural was done by chemical tests and physical properties. Identification was accomplished by a series of spectroscopic and spectrometric techniques.

Bio-inspired gold microtubes based on the morphology of filamentous fungi

This communication describes a general method for templating fungal filaments with gold nanoparticles that results in a gold replica of filaments after calcination of the biological template.