Natural products represent important alternative sources of insecticidal agents for use in the control of insect vectors of human diseases. In a continuation of our quest for novel bioactive plant products, the leaf oil of Croton rhamnifolioides Pax & K. Hoffm. (Euphorbiaceae), a plant widely distributed in the northeast of Brazil, was screened for larvicidal activity and oviposition deterrent effect against the dengue mosquito Aedes aegypti. We also investigated how three years of storage affects the chemical composition of the oil and its biological activities against A. aegypti. The essential oil was extracted from dried leaves of C. rhamnifolioides by hydrodistillation, and the constituents were identified by gas chromatography-mass spectrometry. A total of 57 and 30 components were identified in the aliquots of Fresh and Stocked essential oils, respectively. Sesquicineole (16.79%), a-phellandrene (12.83%) and 1,8-cineole (7.24%) were the majors compounds in aliquots of Fresh essential oil but chemical composition of Stocked essential oil showed the increase of 1,8-cineole (18.61%) and decrease of Sesquicineole (1.77%) but a-phellandrene was maintained the similar amount exhibit in aliquots of Fresh  oil.  The essential oil exhibited substantial larvicidal activity against 4thinstar larvae of A. aegypti in aliquots of Fresh  (LC50=122.35 ppm) and aliquots of Stocked  (LC50 = 89.03 ppm) essential oil. The pure a-phellandrene was strongly active with an LC50= 39.3 ppm. In addition, the effect of leaf oil trypsin-like activity from larvae gut was determined to investigate larvicidal mode-ofaction. Trypsin-like activity from larvae was inhibited in vitro by leaf oil and thus larvicidal effect may involve inhibition of this enzyme. The leaf oil acted as an oviposition deterrent at concentrations of 50 and 100 ppm when tested against gravid females of the dengue mosquito. The results show that a-phellandrene and essential oil of C. rhamnifolioides could find application in a long term as a commercial natural product in the control of A. aegypti and in the management of dengue fever.

Study of the potential a long term of the essential oil from <i>Croton rhamnifolioides</i> (Euphorbiaceae) to control the spread of the mosquito <i>Aedes aegypti</i>

248th National Meeting (2014)

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Study of the potential a long term of the essential oil from Croton rhamnifolioides (Euphorbiaceae) to control the spread of the mosquito Aedes aegypti