Evaluation of larvicidal activity and ecotoxicity of linalool, methyl cinnamate and methyl cinnamate/linalool in combination against Aedes aegypti.

The frequent use of synthetic pesticides to control Aedes aegypti population can lead to environmental and/or human contamination and the emergence of resistant insects. Linalool and methyl cinnamate are presented as an alternative to the synthetic pesticides, since they can exhibit larvicidal, repellent and/or insecticidal activity and are considered safe for use. The aim of this study was to evaluate the larvicidal activity of methyl cinnamate, linalool and methyl cinnamate/linalool in combination (MC-L) (1:4 ratio, respectively) against Aedes aegypti. The in vitro preliminary toxicity through brine shrimp lethality assay and hemolytic activity, and the phytotoxic potential were also investigated to assess the safety of their use as larvicide. Methyl cinnamate showed significant larvicidal activity when compared to linalool (LC50 values of 35.4µg/mL and 275.2µg/mL, respectively) and to MC-L (LC50 138.0µg/mL). Larvae morphological changes subjected to the specified treatments were observed, as the flooding of tracheal system and midgut damage, hindering the larval development and survival. Preliminary in vitro toxicity through brine shrimp showed the high bioactivity of the substances (methyl cinnamate LC50 35.5µg/mL; linalool LC50 96.1µg/mL) and the mixture (MC-L LC50 57.7µg/mL). The results showed that, despite the higher larvicidal activity of methyl cinnamate, the use of MC-L as a larvicide seems to be more appropriate due to its significant larvicidal activity and low toxicity.

Croton argenteus preparation inhibits initial growth, mitochondrial respiration and increase the oxidative stress from Senna occidentalis seedlings.

Senna ocidentalis is a weed, native to Brazil, considered to infest crops and plantations, and is responsible for yield losses of several crops, particularly soybean. The aim of this work was to evaluate if the Croton argenteus extract and fractions possess phytotoxic activity on S. ocidentalis. The crude ethanolic extract (CEE) and its hexanic (HF), chloroformic (CLF) and ethyl acetate (EAF) fractions were tested in germination, growth, oxidative stress increase, Adenosine triphosphate, L-malate and succinate synthesis. The crude extract and its fractions slowed down the germination of S. ocidentalis and decreased the final percentage of germination. Oxidative stress was also increased in the seedlings, by an increase of catalase, peroxidase, superoxide dismutase, glutathione reductase and lipid peroxidation; and it became clear that the ethyl acetate fraction was more phytotoxic. The results indicate that the crude extract and fractions of C. argenteus compromise the mitochondrial energy metabolism, by the inhibition of mitochondrial ATP production, with a decrease in the production of L-malate and succinate. The ethyl acetate fraction of C. argenteus showed high activity on germination and growth, and these effects take place by means of mitochondrial metabolism alterations and increase the oxidative stress, leading the seedling death.

Atividade antibacteriana de Cereus jamacaru DC, Cactaceae / Screening antimicrobial activity of Cereus jamacaru DC, Cactaceae

A procura por novos agentes antimicrobianos a partir de plantas vem sendo intensificada e não existem estudos direcionados à avaliação da atividade antimicrobiana de C. jamacaru frente a microrganismos prejudiciais ao homem. Em vista disso, avaliou-se o efeito antimicrobiano do extrato bruto etanólico do lenho (EBLE) e do córtex (EBCO) desta espécie frente a colônias puras de oito microrganismos patogênicos. Neste estudo foram utilizados os métodos difusão em ágar (meio sólido) e CIM (concentração inibitória mínima). Os resultados obtidos neste ensaio preliminar mostraram que EBCO apresentou atividade antimicrobiana mais pronunciada que EBCE e que os microrganismos cujo crescimento foi mais influenciado por EBCO foram Streptococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa e Escherichia coli.

The search for new antibiotic agents from plants is growing, and no study regarding the activity of C. jamacaru pathological microorganisms has been carried out. This research evaluates the antibiotic effect of crude ethanolic extracts of the cortex (EBCO) and wood (EBLE) of the species over eight microorganisms. Two methods were used: agar diffusion and MIC (minimal inhibitory concentration). EBCO showed better inhibition results than EBLE. Streptococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli are the microorganisms that were better inhibited by EBCO.