Mosquito Larvicidal Activities and Chemical Compositions of the Essential Oils of Leucas Zeylanica Growing Wild in Vietnam

Dengue fever and dengue hemorrhagic fever are hyperendemic to Vietnam with frequent outbreaks and epidemics. Control of the vectors for dengue viruses, Aedes mosquitoes, is critical to maintain control of this disease. In this work, the essential oil of Leucas zeylanica was examined for larvicidal activity against the Aedes mosquito vector. Leucas zeylanica was collected from three different locations in Vietnam. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The essential oil from the aerial parts of L. zeylanica was screened for mosquito larvicidal activity against Aedes aegypti and Aedes albopictus. The major components of L. zeylanica essential oil from Vietnam are beta-caryophyllene, alpha-humulene, germacrene D, beta-selinene, caryophyllene oxide, 1-tetradecanol, and phytol. Leucas zeylanica essential oil showed good larvicidal activity against both Ae. albopictus and Ae. aegypti with median lethal concentration-LC50 (24 hours) values of 67 and 44 mu g/mL, respectively. Thus, L. zeylanica essential oil represents an inexpensive and environmentally benign agent for control of the dengue virus vectors.