Larvicidal Activity of Isodon japonicus var. glaucocalyx (Maxim.) H.W.Li Essential Oil to Aedes aegypti L. and its Chemical Composition
Purpose: To determine the larvicidal activity of the essential oil derived from Isodon japonicus var. glaucocalyx (Maxim.) H.W.Li (Labiatae) aerial parts at flowering stage against the larvae of Aedes aegypti L.
Methods: The essential oil of I. japonicus var. glaucocalyx aerial parts was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromaotography-mas spectrometry (GC-MS). The activity of the essential oil was evaluated, using World Health Organization (WHO) procedures, against the fourth larvae of A. aegypti for 24 h, and larval mortality recorded at various essential oil concentrations ranging from 12.5 - 200 µg/mL.
Results: A total of 34 components of the essential oil of I. japonicus var. glaucocalyx were identified. The principal compounds of the essential oil were thujone (9.65 %), morillol (8.14 %), caryophyllene oxide (7.68 %), β-caryophyllene (7.60 %), α-terpineol (7.22 %), 1,8-cineole (7.09 %), linalool (5.56 %), Z-caryophyllene (5.10 %) and γ-eudesmol (4.71 %). The essential oil exhibited larvicidal activity against A. aegypti with a median lethal concentration (LC50) of 40.82 µg/mL.
Conclusion: The findings indicate that the essential oil of I. japonicus var. glaucocalyx aerial parts has potentials for use in the control of A. aegypti larvae and may be useful in the search for newer, safer and more effective natural compounds for use as larvicides.
Keywords: Isodon japonicus var. glaucocalyx, Aedes aegypti, Larvicidal activity, Mosquito, Essential oil