Toxicity and larvicidal activity on Aedes aegypti of citronella essential oil submitted to enzymatic esterification / Toxicidade e atividade larvicida sobre Aedes aegypti de óleo essencial de citronella submetido à esterificação enzimática

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.

O óleo essencial de citronela (Cymbopogon winterianus) possui diversas atividades biológicas, entre elas a ação repelente a insetos. Alguns estudos mostraram que os ésteres do ácido cinâmico podem ser aplicados como pesticidas naturais, inseticidas e fungicidas. Nesse contexto, o objetivo do presente trabalho foi avaliar a produção de ésteres a partir do óleo essencial de citronela com ácido cinâmico via esterificação enzimática. Além disso, foi investigada a toxicidade do óleo essencial antes e após a esterificação contra Artemia salina e a ação larvicida sobre Aedes aegypti. Os ésteres foram produzidos utilizando ácido cinâmico 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 conversão 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 ésteres. Os resultados demonstraram que as amostras avaliadas apresentam potencial de aplicação como bioinseticida.

Cytotoxicity and antiviral activity evaluation of Cymbopogon spp hydroethanolic extracts

Cymbopogon citratus and C. nardus are noteworthy among the several existing plant species displaying medicinal properties, due to the potential pharmacological activity of these species, including antiviral, antibacterial, antifungal and anti-trypanosomal activities. The objective of this study was to carry out in vitro toxicity tests of plant extracts from both species and analyze potential antiviral activity against Human mastadenovirus serotype 5 (HAdV-5). Two cell lines (A549 and VERO) were used and mitochondrial and lysosomal viability were determined by the MTT and neutral red assay, respectively, after two exposure times (24 hours and six days). The aim of these assays was to counteract the behavior of the extracts against the different cell lines and determine their non-toxic concentration range, in order to evaluate possible antiviral activity against HAdV-5. Plaque reduction and inhibition index of viral titer assays were performed using the maximum non-cytotoxic concentrations (MNCC) of each extract. The results indicate MNCC at 625 µg/mL for all extracts, except for Cymbopogon nardus obtained with 80% ethanol (CN80), which showed toxicity at concentrations higher than 312.5 µg/mL. CN80 was the only extract that displayed potential activity against HAdV-5, at a concentration of 75 µg/mL, becoming a candidate for extract fraction purification and/or the isolation of substances related to the observed antiviral activity

Avaliação preliminar de óleos essenciais de plantas como repelentes para Aedes albopictus (Skuse, 1894) (Diptera: Culicidae) / Preliminary evaluation of plant essential oils as repellents against Aedes albopictus (Skuse, 1894) (Diptera: Culicidae)

Óleos essenciais de plantas têm sido formulados de forma caseira ou colocados no mercado de forma artesanal para repelir mosquitos hematófagos. O presente trabalho avaliou o possível efeito repelente de alguns excipientes normalmente usados em formulações comerciais e de óleos essenciais de nove plantas, sobre fêmeas de Aedes albopictus. Os testes foram realizados em caixas contendo mosquitos, oferecendo-se uma área definida de dedos da mão tratados ou não. Exceto pelo creme Lanatte e os géis de carbopol, as substâncias excipientes avaliadas mostraram ação repelente. Apenas os óleos provenientes de citronela (5 e 10 por cento) resultaram em repelência expressiva, com índices médiosde proteção acimade 98 por cento. Os resultados indicam que a metodologia empregada é adequada para a avaliação preliminar de produtos com potencial para a repelência de mosquitos.

Plant essential oils have been domestically formulated or marketed as handcraft products to repel hematophagous mosquitoes. This work evaluated the possible repellent effect of both excipients normally used in commercial formulations and essential oils from nine plants against Aedes albopictus females. The assays were carried out in boxes containing mosquitoes, where a defined area of treated or non-treated fingers was offered. Except for Lanatte cream and carbopol gels, the evaluated excipients had repellent action. Only the oils from citronella (5 and 10 percent) presented expressive repellent action, with mean protection indexes above 98 percent. The results indicate that the used methodology is appropriate for the preliminary evaluation of products with potential to repel mosquitoes.