Aedes albopictus is an invasive mosquito species, with wide spread in many countries worldwide. The protection from mosquito bites still remains the most effective way to prevent infections associated with moboviruses, such as Zika, Dengue and Chikungunya. In the effort to develop potent mosquito repellents less harmful for humans and the environment, research on natural products with strong bioactivity, such as essential oils, has been prioritized.
In the present work 6 essential oils (EOs) obtained from wood of P. heldreichii and P. nigra, needles of P. pinea, old and fresh fruits of J. phoenicea and fruits of J. oxisedrus have been prepared using Microwave-assisted hydrodistillation. Chemical composition of all EOs were determined by GC/MS analysis. Additionally their repellent properties were evaluated against Aedes albopictus showing that the essential oil of P. pinea and J. phoenicea presented high activity at the dose of 0.2 μL cm(-2). Comparing the results of GC/MS analysis and biological assays we decide to further analyze the EOs of P. pinea and J. phoenicea in order to isolate the main volatile compounds and to identify those responsible for the repellent activity. The fractionation of the selected EOs took place by CPC using for the analysis the biphasic system n-Heptane/ACN/BuOH in ratio 1.6/1.6/0.2 (v/v/v). The results of this step were the isolation of (-) limonene and guaiol from EO of P. pinea and myrcene and germacrene-D from EO of J. oxycedrus. All isolated compounds were tasted for their repellent activity at the dose of 0.2 μL cm (-2). The results of repellant bioassays, employing fractionated compounds, revealed that (-) limonene, guaiol and germacrene D presented high repellent activity, while myrcene was almost non-active.
It is worth noting that the use of CPC for bio-guided isolation of active volatile compounds from EOs is presented for the first time.