In Vitro Characterization and Mosquito (Aedes aegypti) Repellent Activity of Essential-Oils-Loaded Nanoemulsions

The nanoemulsions composed of citronella oil, hairy basil oil, and vetiver oil with mean droplet sizes ranging from 150 to 220 nm were prepared and investigated both in vitro and in vivo. Larger emulsion droplets (195–220 nm) shifted toward a smaller size (150–160 nm) after high-pressure homogenization and resulted in higher release rate. We proposed that thin films obtained from the nanoemulsions with smaller droplet size would have higher integrity, thus increasing the vaporization of essential oils and subsequently prolonging the mosquito repellant activity. The release rates were fitted with Avrami’s equations and n values were in the same range of 0.6 to 1.0, implying that the release of encapsulated limonene was controlled by the diffusion mechanism from the emulsion droplet. By using high-pressure homogenization together with optimum concentrations of 5% (w/w) hairy basil oil, 5% (w/w) vetiver oil (5%), and 10% (w/w) citronella oil could improve physical stability and prolong mosquito protection time to 4.7 h due to the combination of these three essential oils as well as small droplet size of nanoemulsion

Extraction of citronella (Cymbopogon nardus) essential oil using supercritical co2: experimental data and mathematical modeling

Citronella essential oil has more than eighty components, of which the most important ones are citronellal, geranial and limonene. They are present at high concentrations in the oil and are responsible for the repellent properties of the oil. The oil was extracted using supercritical carbon dioxide due to the high selectivity of the solvent. The operational conditions studied varied from 313.15 to 353.15 K for the temperature and the applied pressures were 6.2, 10.0, 15.0 and 180.0 MPa. Better values of efficiency of the extracted oil were obtained at higher pressure conditions. At constant temperature, the amount of extracted oil increased when the pressure increased, but the opposite occurred when the temperature increased at constant pressure. The composition of the essential oil was complex, although there were several main components in the oil and some waxes were presented in the extracted oils above 10.0 MPa. The results were modeled using a mathematical model in a predictive way, reproducing the extraction curves over the maximum time of the process

Essential Oils from Aromatic and Medicinal Plants as Effective Weapons Against Mosquito Vectors of Public Health Importance

The fight against mosquito-borne diseases has recently seen the failure of control programmes based on synthetic chemical treatments to combat larvae and adults of mosquito vectors. This has led to several problems linked to residual substances causing a detrimental impact on environment and human health and to the development of resistance in mosquitoes. In this scenario, new eco-friendly and alternative strategies for the management of mosquito-borne diseases come from the use of plant essential oils (EOs). These are complex mixtures of small, volatile and lipophilic compounds, mostly belonging to monoterpenoids, sesquiterpenoids and phenylpropanoids, produced by aromatic plants belonging to several botanical families such as Apiaceae, Asteraceae, Geraniaceae, Lamiaceae, Lauraceae, Myrtaceae, Poaceae, Rutaceae, Verbenaceae and Zingiberaceae. An important ecological role played by EOs is defending plants from several enemies such as bacterial and fungal pathogens, viruses, insects and parasites. EOs represent ideal candidate ingredients to be incorporated in insecticidal formulations since scientific evidences have documented their efficacy against larvae and adults of several mosquitoes (e.g. Anopheles, Aedes and Culex) even at low doses (<50 ppm), the multiple mode of action and wide spectrum of efficacy, the low toxicity on nontarget organisms and environment and the unlikely capacity to induce insect resistance. In this chapter, we gave an overview of the most important EOs obtained from commercially important botanical families with documented efficacy against mosquito vectors. Particular attention has been paid to highlight their strengths and weakness and the future challenges leading to the replacement of conventional insecticides by agrochemical companies