Oviposition deterrent activity of hydrolate, aqueous extract and major constituents of essential oil from the leaves of Eugenia uniflora (Myrtaceae) for the control of Aedes aegypti

Aedes aegypti is the main vector of arboviral diseases, such as dengue, Zika and chikungunya. The emergence of resistance to synthetic insecticides constitutes an important obstacle to combating the mosquito. Thus, studies have investigated the potential of natural products as an alternative to synthetic chemicals. The aim of the present study was to evaluate the oviposition deterrent activity of different products extracted from the leaves of Eugenia uniflora, which is a native species of Brazil with known bioactive properties but explored little for the control of A. aegypti. The major constituents identified in the essential oil from E. uniflora by gas chromatography coupled to mass spectrometry were selina-1,3,7(11)-trien-8-one (65.83%) and selina-1,3,7(11)-trien-8-one epoxide (13.53%). These major constituents were also identified in the dynamic headspace of the hydrolate and aqueous extract and in the ether fraction of the aqueous extract together with pyrogallol. Other classes of secondary metabolites were also identified in the aqueous extract using high-performance liquid chromatog-raphy, such as gallic acid, myricetrin and ellagic acid. The results of the bioassays suggest significant oviposition deterrent activity for the essential oil at concentrations of 9-36 ppm, the isolated substance selina-1,3,7(11)-trien-8-one epoxide at 3.6 ppm, the aqueous extract at 51% (v/v) and hydrolate at 53% (v/v). The magnitude of oviposition deterrent activity for the products extracted from the leaves of E. uniflora, especially the hydrolate and aqueous extract, was one of the most notable ever reported for the inhibition of oviposition by gravid females of A. aegypti. The aqueous extract and hydrolate achieved greater than 90% inhibition. Moreover, the minimum concentration (3.6 ppm) with deterrent activity found for the substance isolated from the essential oil: selina-1,3,7(11)-trien-8-one epoxide -is one of the lowest ever described in the literature.