Toxicity and larvicidal activity on Aedes aegypti of citronella essential oil submitted to enzymatic esterification

Abstract

The essential oil of citronella (Cymbopogon winterianus) has several biological activities, among them the insect repellent action. Some studies showed that cinnamic acid esters can be applied as natural pesticides, insecticides and fungicides. In this context, the objective of the present work was to evaluate the production of esters from citronella essential oil with cinnamic acid via enzymatic esterification. Besides, the essential oil toxicity before and after esterification against Artemia salina and larvicidal action on Aedes aegypti was investigated. Esters were produced using cinnamic acid as the acylating agent and citronella essential oil (3:1) in heptane and 15 wt% NS 88011 enzyme as biocatalysts, at 70 °C and 150 rpm. Conversion rates of citronellyl and geranyl cinnamates were 58.7 and 69.0% for NS 88011, respectively. For the toxicity to Artemia salina LC₅₀ results of 5.29 µg mL^-1 were obtained for the essential oil and 4.36 µg mL^-1 for the esterified oils obtained with NS 88011. In the insecticidal activity against Aedes aegypti larvae, was obtained LC₅₀ of 111.84 µg mL^-1 for the essential oil of citronella and 86.30 µg mL^-1 for the esterified oils obtained with the enzyme NS 88011, indicating high toxicity of the esters. The results demonstrated that the evaluated samples present potential of application as bioinsecticide.

Alternate abstract:

O óleo essencial de citronela (Cymbopogon winterianus) possui diversas atividades biológicas, entre elas a açâo repelente a insetos. Alguns estudos mostraram que os esteres do ácido cinámico podem ser aplicados como pesticidas naturais, inseticidas e fungicidas. Nesse contexto, o objetivo do presente trabalho foi avaliar a produçâo de esteres a partir do óleo essencial de citronela com ácido cinámico via esterificaçao enzimática. Além disso, foi investigada a toxicidade do óleo essencial antes e após a esterificaçao contra Artemia salina e a açao larvicida sobre Aedes aegypti. Os esteres foram produzidos utilizando ácido cinámico como agente acilante e óleo essencial de citronela (3: 1) em heptano e 15% em peso da enzima NS 88011 como biocatalisadores, a 70 ° C e 150 rpm. As taxas de conversao de cinamatos de citronelil e geranil foram 58,7 e 69,0% para NS 88011, respectivamente. Para a toxicidade sobre Artemia salina foram obtidos CL₅₀ de 5,29 µg mL^-1 para o óleo essencial e 4,36 µg mL^-1 para os óleos esterificados com NS 88011. Na atividade inseticida contra larvas de Aedes aegypti, obteve-se CL₅₀ de 111,84 µg mL^-1 para o óleo essencial de citronela e 86,30 µg mL^-1 para os óleos esterificados com a enzima NS 88011, indicando alta toxicidade dos esteres. Os resultados demonstraram que as amostras avaliadas apresentam potencial de aplicaçao como bioinseticida.