Abstract
Although numerous reports are available concerning the larvicidal potential of essential oils, very few investigations have focused on their mechanisms of action. In the present study, we have investigated the chemical composition of the leaf oil of Croton rhamnifolioides during storage and its effects on oviposition and survival of larvae of the dengue fever mosquito Aedes aegypti. In addition, we have established a possible mechanism of action for the larvicidal activity of the essential oil. GC-MS analyses revealed marked differences in the composition of oil that had been freshly isolated and that of a sample that had been stored in a sealed amber-glass vial under refrigeration for three years. However, both fresh and stored oil exhibited substantial larvicidal activities with LC50 values of 122.35 and 89.03 ppm, respectively, and oviposition deterrent effects against gravid females at concentrations of 50 and 100 µg·mL−1. These results demonstrate that the larvicidal effect of the essential oil was unchanged during three years of storage even though its chemical composition altered. Hence, the essential oil could be used in the preparation of commercial products. In addition, we observed that the trypsin-like activity of mosquito larvae was inhibited in vitro by the essential oil of C. rhamnifolioides, suggesting that the larvicidal effect may be associated with inhibition of this enzyme.
Highlights
Croton is a major genus of the family Euphorbiaceae and comprises some 1200 species of trees, shrubs and herbs that are widely distributed in tropical regions [1]
The characteristic features of the essential oil of C. rhamnifolioides obtained in the present study resembled those reported for various species of Croton, including C. heliotropiifolius and C. pulegiodorus [37], C. argyrophylloides and
The results revealed that the leaf oil inhibited trypsin-like activity of 4th instar A. aegypti in a dose-dependent manner (Figure 1), and this inhibitory effect may be associated with larvicidal activity
Summary
Croton is a major genus of the family Euphorbiaceae and comprises some 1200 species of trees, shrubs and herbs that are widely distributed in tropical regions [1]. Has been identified in several areas of the Brazilian Caatinga [20], a biome that is characterized by high temperatures with long and irregular periods of drought This xerophytic shrub is used in folk medicine to treat stomach disorders, vomiting, hemorrhagic diarrhea and fever [21]. Navarro et al [36] demonstrated that the leaf oils obtained from members of the families Lauraceae and Piperaceae exhibited strong larvicidal activities (LC50 below 20 and ppm, respectively). The present paper aimed to (i) determine the chemical composition of the essential oil from leaves of C. rhamnifolioides and (ii) assess the influence of storage on the biological activities of. C. rhamnifolioides in controlling the spread of A. aegypti is described for the first time together with a possible mechanism of action
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