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 (LC
50) 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.
