Efeito larvicida e ovocida de extratos de Crotalaria pallida sobre o vetor Aedes aegypti

Abstract

Insecticide resistance has caused difficulties in controlling Aedes aegypti, stimulating the search for natural larvicide compounds. Crotalaria pallida, popularly known as Chique-Chique and for its repellent action, still lacks scientific data regarding its properties. The objective was to verify the larvicidal/ovocidal potential of this plant in A. aegypti. C. pallida leaves were subjected to extraction with solvents: Ethyl Acetate (AcEt), Hexane (Hex) Ethanol (EtOH) and Methanol (MetOH). Larvicidal action was determined with 15 larvae (L2, Rockefeller strain) through contact with each extract (500, 250; 125; 62.5; 31.25 mg/L diluted in dimethyl sulfoxide (DMSO) for 24 hours (triplicate tests)) with subsequent determination of the lethal dose (DL90 and DL50) .The LD50 was used to determine the larvicidal action in the different larval instars for the extracts with greater lethality. at 500 mg/L) for 10 minutes and subsequently transferred to clean water for hatching (Contact Test). Eggs were also hatched in water containing 500 mg/L of the extracts (Hatching test). All results were subjected to statistical analysis, a better larvicidal action was observed, with death of 100% and 88.8%, in the compounds MetOH and EtOH, respectively, at a concentration of 500 mg/L.

Biocidal Activity of a Nanoemulsion Containing Essential Oil from Protium heptaphyllum Resin against Aedes aegypti (Diptera: Culicidae)

“…The stiffness of the chorion increases when they become older and this is responsible for their resistance to dehydration, extreme temperatures and ultraviolet radiation and their tolerance to the action of pathogens and products with ovicidal activity, contributing to the effective control of the mosquito [15]. Some external factors can interfere with ovicidal activity such as the age of the egg, the concentration and the period of exposure to the products used in the control [16]. A study carried out with Crotalaria pallida inhibited the hatching of eggs by 95% through the methanolic extract, by 90% in the ethanolic extract by contact and by 100% in the hatching test at a concentration of 500 µg•mL −1 [16].…”

“…Some external factors can interfere with ovicidal activity such as the age of the egg, the concentration and the period of exposure to the products used in the control [16]. A study carried out with Crotalaria pallida inhibited the hatching of eggs by 95% through the methanolic extract, by 90% in the ethanolic extract by contact and by 100% in the hatching test at a concentration of 500 µg•mL −1 [16]. In another study, the essential oils of Ricinus communis and Cnidoscolus phyllacantus influenced the embryogenesis of A. aegypti eggs and presented hatching rates of 60% for R.communis and 95% for C. phyllacantus [17].…”

“…The extract of Annona coriacea showed a low mortality for the adulticidal activity to A. aegypti; the observed mortality at 1000 µg•mL −1 was only 6.6% [13]. Researchers performed an adulticidal assay with the nanoformulation of Heliotropium indicum, which showed 98.2% mortality to A. aegypti mosquitoes at 250 µg•mL −1 in 24 h of exposure [16].…”

Constituintes químicos e potencial larvicida frente Aedes aegypti do óleo essencial de Origanum vulgare L.

“…Os óleos essenciais podem ser obtidos a partir da planta inteira ou parte dela, por meio de extração com diferentes tipos de solventes, podendo ter toxicidade para as formas adultas do mosquito (inseticida), para os estágios larvais (larvicidas), inibindo o crescimento e diferenciação das mesmas, bem como inibindo a maturação e/ou eclosão dos ovos (ovocida) (Takagi, 2020). Os óleos essenciais apresentam uma composição relativamente complexa, podendo possuir entre dezenas a centenas de compostos, e em geral o fitoconstituinte em maior concentração é aquele que atribui à atividade biológica do óleo essencial (Cunha et al, 2012).…”