Toxicity and larvicidal activity on Aedes aegypti of citronella essential oil submitted to enzymatic esterification/Toxicidade e atividade larvicida sobre Aedes aegypti de oleo essencial de citronella submetido a esterificalo enzimatica

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 [degrees]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 [LC.sub.50] results of 5.29 [micro]g [mL.sup.-1] were obtained for the essential oil and 4.36 [micro]g [mL.sup.-1] for the esterified oils obtained with NS 88011. In the insecticidal activity against Aedes aegypti larvae, was obtained [LC.sub.50] of 111.84 [micro]g [mL.sup.-1] for the essential oil of citronella and 86.30 [micro]g [mL.sup.-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.