CHEMICAL CONSTITUENTS AND LARVICIDAL ACTIVITY OF VOLATILE OIL FROM Solenostemon monostachyus (P Beauv.) Briq. AGAINST Anopheles gambiae

Abstract

Synthetic larvicides have been used to control malarial vector. However, increasing resistance of
mosquito larvae to the synthetic larvicides poses great problem in the vector control. Natural
control with plant essential oil may serve as an alternative. This study investigates the chemical
constituents and larvicidal activity of volatile oil obtained from Solenostemon monostachyus
against the larvae of Anopheles gambiae. The volatile oils were extracted using hydro-distillation
in a Clevenger type apparatus and analyzed using GC-MS. The larvicidal assay was carried out
against Anopheles gambiae larvae at concentration range of 12.5- 400 μg/mL. The analysis of
the volatile oil showed that the major constituents of the oil were Caryophyllene oxide (21.6%),
β-Caryophyllene (19.6%), β-Pinene (9.8%) and Germacrene D (7.3%). Results showed that
larval mortality increases with increasing exposure period to the volatile oils from S.
monostachyus. The larvicidal activity demonstrated that the mosquito larvae were susceptible to
the volatile oil with LC50 of 23.44 μg/mL. The results suggest that S. monostachyus essential oil
has potentials for the control of Anopheles gambiae. Therefore the plant may serve as a potential
source of raw material for a new and eco-friendly larvicide.